1976 Sprint V mechanical rebuild
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Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Fri Nov 09, 2018 3:27 pm quote
First start, just to see...

The fuel tank was leaking when I first filled it up, so I need to see if the tap is leaking or the fuel line is cracked, as it's basically petrified.

A lot of white smoke at first, but that cleared up after it ran for a few minutes.

I took it for a ride around the block and the ride was just really smooth. Much slower than I'm used to, and I didn't really push it since I only swapped out one tire, but from that two minutes of riding, I like it a lot.

Next will probably be pulling the tank and cleaning out the autolube. I'll swap it over to 12v. It had the wiring harness replaced, but the ignition is still the original points. That will turn into a SIP Variable Timing ignition soon enough, along with the engine rebuild.

Let the fun begin!

Last edited by chandlerman on Tue Nov 20, 2018 6:44 pm; edited 1 time in total
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Fri Nov 09, 2018 5:22 pm quote
First parts orders placed. Engine rebuild bits, plus a SIP Road XL and 60mm Mazzi crank. Clauss Mounts for the motor and rear shock. A new 6v battery from Amazon.

I'll use the Polini 177 that's sitting on the shelf for a top end, keep the stock gearing. Maybe swap the clutch out at some point.

No ignition upgrade for the moment, because the SIP Sport Ignition is out of stock and that's an easy swap later. No shocks, rims, or tires, either, because I have a couple of spare Continental Zippy 1's already sitting on rims. I just needed an inner tube for one of them.j

And no front disc, which will probably happen at the same time as I replace the shocks since I'll be going the PK fork route.

And for the moment, I'll probably pull the 24/24 carb off the VBB and install that until I eventually go to a PWK 28 or 30 (again, becauseI have those lying around).

My goal is to get reliably back on the road, then worry about the less intrusive (i.e. cosmetic or no case splitting) upgrades later.
Molto Verboso
08 GTS 250, 79 P200E, 62 Allstate
Joined: 11 Jan 2006
Posts: 1048
Location: Florence, OR
Fri Nov 09, 2018 7:56 pm quote
SCORE - It runs! Very nice. Now for the general stuff (fuel line, tires, etc) and at least you'll be rolling. I'll be watching what you do.

BTW, is that a Pinasco tubless split rim on the Stella I saw in the vid? If so, how are you liking them? I'm thinking of getting a set myself...
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Sat Nov 10, 2018 4:42 am quote
qascooter wrote:
SCORE - It runs! Very nice. Now for the general stuff (fuel line, tires, etc) and at least you'll be rolling. I'll be watching what you do.
The biggest problem right now is that I don't have enough room in my garage because of the boat project, which is inside the plastic sheeting in all the recent pictures.

It's pretty sad when I've gone from no workshop (I was, literally, a shade tree mechanic for three years before moving into this house) to "oh, my two car garage workshop isn't big enough for all my toys!"

So next up is probably some workspace cleaning, at least getting my workbench cleared off, so I can pull the motor and see what's up inside the cases. I know that the previous owner never rebuilt the motor. He owned it for 25 years and put 7,000 miles on it, but the transmission was super-smooth yesterday, so to me that's a very good sign.

You can see a LOT of white smoke in that video, which might just be crud from sitting for ten years, but given that he originally asked me about help with getting the carb to dial in, I'm guessing leaky clutch side seal. Either way, it's getting replaced once the SIP Fairy arrives.

And I'll be replacing the motor mounts, too, since I'm pretty certain that they and the top rear shock mount are all going to be shot to hell since he also told me that he and his wife used to ride two-up a lot, and he's over six feet.
qascooter wrote:
BTW, is that a Pinasco tubless split rim on the Stella I saw in the vid? If so, how are you liking them? I'm thinking of getting a set myself...
Yes, it is. I bought a pair of them four or five years ago, then had to replace one when it got loose on the hub and damages the mounting holes. The newer generation version goes together a lot better, but is a millimeter too tight for the front hub on the Stella.

All three of them have had a tendency for intermittent slow leaks, I assume along the split.

They have not held up to general wear & tear as much as I would have liked, but they're significantly lighter and noticeably better balanced at higher speeds.

I've been tempted to try the SIP Tubeless rims, especially now that they'll ship them with tires pre-mounted, but that's a fair ways down the scooter budget list right now, what with a couple grand worth of brakes, suspension, ignition, and probably more engine upgrades beyond the long stroke and basic rebuild bits I've already ordered for this current adventure.
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6839
Location: Victoria, Australia
Mon Nov 19, 2018 11:32 pm quote
Looks like a great project Chandler! Should be good fun.
Do you have the Clauss mounts on your VBB? I tried them on the Super and had to take them out, waaay too much vibration. But I haven't heard anyone with a P complain about them.

I recently had a Pinasco wheel come off... I had done about 400km since tightening the wheel nuts. But they came loose and eventually fell off altogether. Funny thing was I didn't notice anything strange until suddenly I was skidding along with the wheel jammed up in behind the hub and the scooter simply stopped. The stud holes were all enlarged by this time. I've ordered another one but I'll be looking for another type of nut this time!
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Tue Nov 20, 2018 7:10 pm quote
I thought I'd posted a reply this morning, but it seems to have been eaten by The Internet Gods, so...
Ginch wrote:
Looks like a great project Chandler! Should be good fun.
Do you have the Clauss mounts on your VBB? I tried them on the Super and had to take them out, waaay too much vibration. But I haven't heard anyone with a P complain about them.
I have them in my Stella, but not my VBB. I've been pleased with them on the Stella, so I'm going to go with them again.
Ginch wrote:
I recently had a Pinasco wheel come off... I had done about 400km since tightening the wheel nuts. But they came loose and eventually fell off altogether. Funny thing was I didn't notice anything strange until suddenly I was skidding along with the wheel jammed up in behind the hub and the scooter simply stopped. The stud holes were all enlarged by this time. I've ordered another one but I'll be looking for another type of nut this time!
I had a similar issue. It felt like the rear hub nut had come loose, but when I went to check it, several lug nuts were loose and the rim was trashed.

I replaced the rim and the newer version had several engineering changes, most of them related to making bolting the halves together easier, and some that might have been cosmetic, or maybe just simplified manufacturing. It was also a tiny bit tight on the hub, but not so tight it couldn't be persuaded on with a tiny bit of love from a dead blow hammer.

IMG_20181120_153649.jpg
Trashed :(

Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Tue Nov 20, 2018 7:39 pm quote
Also, this afternoon I pulled the tank for general cleaning (it has a little loose crud, but not much rust; oil tank just needs cleaning) and to replace the fuel tap with a faster flow.

I also dropped the motor. Crankcase oil was gas-free, which surprised me a little. I guess all the white smoke when I fired it up was just from sitting for ten years.

With the motor out, the frame is amazingly light. I was able to easily hoist it by the tail with one hand after the centerstand slipped and folded up while I was dropping the motor. I think it's even lighter than the VBB, if that's possible.

The fuel line was basically petrified, to the point I couldn't even pull it out and had to cut it when I pulled the tank. The shocks are looking pretty dodgy, so maybe I'll do the rear since I'm replacing the mount, then suck it up on the front until I put the disc brake on.

The rubbing on the clutch cover is from the stick-on whitewalls the PO had which had come un-stuck.

I'm still working around the boat hull painting, but I figure that tomorrow I'll get my workbench cleaned up so I can split the cases and see what I failed to order first time around in the way of rebuild parts. Thus far, the only thing I've realized I forgot is clutch plates and new cables, neither of which are show stoppers for the engine rebuild.

And a guy I work with has a sandblasting cage and powercoating rig, so I'll probably hook up with him to do the wheel rims and hubs. I'm still thinking black for those.

Who knows. I might be rolling before the snow gets too deep yet!

IMG_20181120_153622.jpg
Definitely not VaderKleen!

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Naked frame

Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Mon Jan 07, 2019 2:52 pm quote
It begins...
I decided to move my project thread over to, well, my project thread.

Hopefully it won't wind up as long as some build threads .

I started the teardown on Saturday morning and provided my initial update over in Today, I...
chandlerman wrote:
I finally started the teardown on my Sprint's motor yesterday.

First up was scraping off all the crud, which took an hour or two by itself. It still needs more cleaning, but at least it's not a total muddy/greasy mess so I can work on it.

I don't think it had ever been opened up before, but it definitely needed a rebuild. Leaks on every seal, but almost no wear on things like the cruciform or gears. Maybe it's just how I build and ride my bikes, but this thing shows less wear on the gears and cruciform after at least 25 years (PO never rebuilt it) than I get in a year.

Assuming that I don't get pulled into too many other things, today will hopefully see me finishing the tear down and building up the cases around the ports with JB Weld prior to tearing into them with the ol' Dremel.

I also decided after watching The latest (ep 34) of That Scooter Thing that I'd go ahead and get a Vape ignition for it rather than mess with points and 6v. I have a few other things I need to get from SIP anyway (brake shoes? those wear out?), so why not, other than, well, money?
And yesterday's update...
chandlerman wrote:
Finished the teardown this morning, then cleaned the cases and JBWeld'ed around the ports.

I also went a little bit crazy over at SIP.

The build plan is now:
- Polini 177
- 60mm Mazzi cut crank
- 24/24e with the fuel passage drilled out
- Polini Venturi carb adapter
- SIP (Vape) variable timing ignition
- Full DC & 12v conversion
- SIP RoadXL
- Clauss Mounts

I'll keep the autolube and see where all that gets me.
But future updates will live here.

Next up is porting, grinding down the excess of JBWeld that I put around the ports, and then assembly. Maybe not until Friday, but maybe earlier. Now that it's under way, I'm pretty fired to get things rolling.

My biggest challenge is that SIP didn't get my order shipped today, so I could be waiting for parts over the weekend. Luckily, nothing that will keep me from getting the cases buttoned up, though.

IMG_20190105_073635.jpg
Ready to go!

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Head leak. My personal nemesis.

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Now we're getting somewhere!

IMG_20190105_111319.jpg
But it still started and ran before I pulled the motor off the bike. Compression was not all it could have been, though...

Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1055
Location: UK (South East)
Tue Jan 08, 2019 3:37 am quote
Chandlerman, I was surprised to see what looks like a narrow taper crank in a 1976 Sprint V motor. I thought Piaggio had transitioned to the P style crank by then. There's a lot of material around the transfers on those older 3 ports. I doubt you'll need the JB Weld.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Tue Jan 08, 2019 6:15 am quote
swa45 wrote:
Chandlerman, I was surprised to see what looks like a narrow taper crank in a 1976 Sprint V motor. I thought Piaggio had transitioned to the P style crank by then. There's a lot of material around the transfers on those older 3 ports. I doubt you'll need the JB Weld.
To be honest, I hadn't really considered the crank taper. I'll measure it when I get home and confirm. It used the self-extracting flywheel though, which actually worked just fine, a bit to my surprise after having a terrible time with the one on my VBB.

Yes, the JBWeld is overkill (it's *really* overkill), but it's soooo much easier to do it now when the cases are clean and de-greased and then not need it. A lot of it will be getting dremeled off, for sure. I didn't realize how much I'd overkilled it until I put the cylinder on and saw the excess.

I had the Polini on my Stella previously and matched its ports to the Stella cases at the time, so I was kind've beholden to those openings as a result. Looking at what I have, I'm in good shape. A little bit on that upper transfer would have been plenty, but I also don't have to worry about breaking through this way, either.

And in less happy news, the expected delivery date on my SIP order is not until Monday, although it's been known to arrive a day early, or go to the FedEx distribution center, which is about ten minutes from my house. Either way, Meh.

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Look at that beautiful rotary pad!

IMG_20190108_073220-porting.jpg
Big ol' ports

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6839
Location: Victoria, Australia
Tue Jan 08, 2019 5:49 pm quote
That pad looks great! Nice motor you got there.

I have 74 and a 75 Super motors (according to the Scooterhelp calculator - although Rob Hodge has said that there is some wiggle room on the dates given) and one has the P type flywheel side bearing and the other doesn't.
Both have the narrow taper though. So looks like there was another step between these late motors and the P.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Sun Jan 13, 2019 6:09 pm quote
Today was Dremel Day.

Spent a few hours in the garage opening up the ports, cutting out the gates in the cylinder, porting and flowing the airbox into the cases for the 24/24, and rounding out a few edges.

I have a couple spots to touch up, then

Naturally, I managed to break through the ports on each side, so I had the pleasure of fixing those spots. I should get a JBWeld endorsement.

I'll clean up the JBWeld, polish it all a little bit, and then it'll be good-to-go.

Almost ready for the re-assembly to begin!

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Before

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After

IMG_20190113_153726-cropped.jpg
I like big ports and I cannot lie

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6839
Location: Victoria, Australia
Sun Jan 13, 2019 8:50 pm quote
I do often wonder what the right shape for the base of the transfers is. Thinking about it, I wonder if digging them out with a relatively sharp radius at the bottom is really the best? I imagine the flow would be smoother with a gentler path from case to cylinder.

CYLINDER.jpg

Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1055
Location: UK (South East)
Mon Jan 14, 2019 12:46 am quote
I would assume that volume is equally important, but only if you have the inlet/crank/carb combo that can create the requisite volume of charge in the first place. Otherwise, flow, as you say would surely be better with the sloping port sides.

The added benefit would be little or no need for JB Weld !!
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1202
Location: London UK
Mon Jan 14, 2019 12:57 am quote
Looking like good progress. Shape is not as important as big. There should be no sharp edges or right angles all those parts should be radiused. Round edges create less turbulance.

What port timing you aiming for?
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Mon Jan 14, 2019 7:09 am quote
I'm going for a torque-y build, so probably 123-1225 TD, see what that gets me in terms of exhaust duration and blowdown. I'm hoping to get through the metal-shaving-making portion of the show maybe this week

I decided to keep the SI carb and autolube for this build, so I'm going to run a 24/24e with the DRT modifications that just arrived from SIP, along with a Polini venturi on the intake.

I matched the airbox to the carb and flowed the carb opening into the airbox and cases yesterday, too. Still needs to get final sanding, but it's coming along nicely.

This biggest mystery for me at this point is intake timings. I went with the Long Stroke Mazzi Cut Crank, which is timed at 138/6 post TDC, per SIP's product page, but will have to measure actuals. I didn't molest the intake port at all other than to straighten the edges.

As to transfer shape, I'm thinking shallow going forward, if only because I'm tired of breaking through the cases and having to break out the JBWeld.

IMG_20190113_153850-cropped.jpg

Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4600
Location: So Cal
Mon Jan 14, 2019 10:49 am quote
I know what you're saying Ginch ... I'm also wondering if maybe "big" isn't necessarily the most important part of the porting game.

I'm thinking velocity may be equally, or more important ... you want the mix to get sucked in there fast and get swooped around quickly. Opening up a port increases volume, but slows velocity because the area of highest velocity is being spread across a larger area. Think of putting your thumb over a garden hose.

I could be wrong but I think shaping for velocity - if done carefully - might make more usable power than just gouging out giantic ports.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Mon Jan 14, 2019 11:33 am quote
SoCalGuy wrote:
I could be wrong but I think shaping for velocity - if done carefully - might make more usable power than just gouging out giantic ports.
Heresy!
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6839
Location: Victoria, Australia
Mon Jan 14, 2019 6:10 pm quote
SoCalGuy wrote:
I know what you're saying Ginch ... I'm also wondering if maybe "big" isn't necessarily the most important part of the porting game.

I'm thinking velocity may be equally, or more important ... you want the mix to get sucked in there fast and get swooped around quickly. Opening up a port increases volume, but slows velocity because the area of highest velocity is being spread across a larger area. Think of putting your thumb over a garden hose.

I could be wrong but I think shaping for velocity - if done carefully - might make more usable power than just gouging out gigantic ports.
Well this is pretty much exactly what I was told. When I had my old Polini cylinder I found a guy to rebore it. His main gig though was making sleeves for 2 stroke racing dirt bikes. His advice - based on a colleague's flow bench testing - was that you don't want to enlarge the transfers so much that what you said happens. He was talking about regular motorcycle transfers however, and not piddly Vespa ones which are clearly a lot smaller.
My recent projects have reeds so volume is easily addressed so I'm not so concerned about finding volume in the transfers. Plus of course what Chandlerman says about breaking through.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Mon Jan 21, 2019 2:48 pm quote
I'll do a proper write-up later, but despite a major winter storm that started Friday and continued through the rush hour this morning, I was able to complete the porting of the cases, cylinder and piston.

I also discovered that I accidentally ordered the wrong motor mounts/bushings, so I had to order a fresh set of those. Meh. At least the wrong ones will fit in one of my other motors.

At this point, I'm ready to begin the re-assembly process, but it's hard to get motivated to head out to the garage when temps are in the single digits Fahrenheit. With a propane heater & space heater going full blast, I got the temp up to about 35f, then just bundled up and suffered for my art.

I also realized that I wouldn't need to put my bearings in the freezer to shrink them for insertion, I could just set them outside. (Please note, I do not recommend this approach, as it requires living somewhere that the temperatures get as low as in your freezer).

I'm also thinking I got a little over-excited with opening up the cylinder gates to match the piston. it's interesting to me how much mis-match there is between the cylinder, case, and piston ports if simply bolted on. If you're not going to do porting work, you mght as well save your money.

Photos to come, but right now, I'm fighting with my cloud sync and can't find a USB cable, so you'll have to wait on those.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1202
Location: London UK
Mon Jan 21, 2019 8:11 pm quote
SoCalGuy wrote:
I know what you're saying Ginch ... I'm also wondering if maybe "big" isn't necessarily the most important part of the porting game.

I'm thinking velocity may be equally, or more important ... you want the mix to get sucked in there fast and get swooped around quickly. Opening up a port increases volume, but slows velocity because the area of highest velocity is being spread across a larger area. Think of putting your thumb over a garden hose.

I could be wrong but I think shaping for velocity - if done carefully - might make more usable power than just gouging out giantic ports.
The one issue with transfer velocity is that the quicker the mixture goes in, the quicker it goes straight out of the exhaust. In the trade they call this 'short circuit loss'.
In an ideal situation the transferred mixture should enter bump the stream from the opposite port and stop, sit there while the last of the exhaust flows across above it and wait for the piston to move up and close the exhaust. At rpm above 7000 it occurs less as the exhaust helps keep it in but when down at 5000rpm too much escapes and there is no torque. Big ports with big volume to move the most mixture in the slowest way tends to make the most power. Difficult to translate to our engines but we try.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Mon Jan 21, 2019 8:20 pm quote
I won the battle with my file sync'ing. I could explain it, but you'd all just get bored and wander off to some other thread.

Anyways...

I opened up the ports on the Polini to match the cases on my Stella, then decided I didn't like it that much and ordered another BGM 177 for that bike.

There was a lot more work to do on that jug and piston, however, so I really didn't give it a fair shake. Since this project was both a bit of a bluebird, and because there's lots of other stuff I need to do, I decided to re-use it since it was nearly new.

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First, mark it at BDC to see the potential.

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Unmolested piston skirt

IMG_20190120_135725-marked up.jpg
In the course of my work, I noticed a few things about how poorly the Polini piston and cylinder work together. To start with, as originally built, there's a little tiny port through the piston into the cylinder port, and most of it is covered by the ski

IMG_20190120_171149.jpg
Let my piston breathe!

So I knew I was going to have some work to do opening up the piston. I look at a Malossi or BGM piston, and can see how much more room to work there is in there.

I finished up the piston, opening up all the ports and cutting back

IMG_20190120_184249-marked.jpg
And that's when I got a little over-aggressive.

"Hey," I thought, "the cylinder skirt still covers part of that piston port. Let's fix that!"

so I opened up the skirt, the upper transfer ports, and blended it all together.

IMG_20190120_183115-marked.jpg
It was beautiful, only with one problem. There was not way to flow it into the cases, because the pesky cylinder studs were in the way.

It seemed like a good idea at the time, but now I'm just stuck with an area that's going to be turbulent. Boo.

So,

forecast..JPG
Next up is reassembly, where my hands and my scooter parts will re-enact the flagpole scene from A Christmas Story* as I work in stupid-cold, possibly single-digit temps to keep this ball rolling.

This is my current weather forecast. I'm an idiot for li

Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Mon Jan 21, 2019 8:24 pm quote
Jack221 wrote:
The one issue with transfer velocity is that the quicker the mixture goes in, the quicker it goes straight out of the exhaust. In the trade they call this 'short circuit loss'.
In an ideal situation the transferred mixture should enter bump the stream from the opposite port and stop, sit there while the last of the exhaust flows across above it and wait for the piston to move up and close the exhaust. At rpm above 7000 it occurs less as the exhaust helps keep it in but when down at 5000rpm too much escapes and there is no torque. Big ports with big volume to move the most mixture in the slowest way tends to make the most power. Difficult to translate to our engines but we try.
Isn't the angle of the port roofs a big factor in preventing short circuit loss?

It's also one of those attributes that we are (or at least, I am) pretty much at the mercy of the original manufacturers to control.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1202
Location: London UK
Mon Jan 21, 2019 8:30 pm quote
chandlerman wrote:
I'm going for a torque-y build, so probably 123-125 TD, see what that gets me in terms of exhaust duration and blowdown. I'm hoping to get through the metal-shaving-making portion of the show maybe this week

This biggest mystery for me at this point is intake timings. I went with the Long Stroke Mazzi Cut Crank, which is timed at 138/6 post TDC, per SIP's product page, but will have to measure actuals. I didn't molest the intake port at all other than to straighten the edges.
124TD would be exactly correct for the primary transfers this kind of build. I hope you didn't move the secondaries.

The case inlet port will make more power if bigger. These older engines have quite small inlets as stock. The rotary pad can be widened to 1.5mm overlap and at the rear taken to 5mm from the edge. Your crank choice is a little sporty but will be ok. If you get about 180 degrees total duration on that old motor you're in the touring ballpark.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Mon Jan 21, 2019 8:43 pm quote
Jack221 wrote:
124TD would be exactly correct for the primary transfers this kind of build. I hope you didn't move the secondaries.
I left the port timings alone. I looked at widening the exhaust port a little, but decided to leave it alone.
Jack221 wrote:
The case inlet port will make more power if bigger. These older engines have quite small inlets as stock. The rotary pad can be widened to 1.5mm overlap and at the rear taken to 5mm from the edge.
I've done all my more serious tuning thus far on LML's with reeds, so porting the inlet is still a bit of a mystery to me, and I haven't done much in the way of research on it.

Even basic stuff like the recommended sealing surface width, for example.

At this point, though, I'd rather leave a little power on the table than force myself to a reed, even if I have a PWK 30 sitting on the shelf
Jack221 wrote:
Your crank choice is a little sporty but will be ok. If you get about 180 degrees total duration on that old motor you're in the touring ballpark.
Not that it will matter this time around, but what would have been a better crank choice for a build like this?
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1202
Location: London UK
Mon Jan 21, 2019 8:44 pm quote
Looking like fine progress. If you haven't already, hold the cylinder and case half together and go in with a small sanding drum all those edges can be smoothed out.

Short circuit loss is the big issue for low rpm motors. On higher rpm motors 12000 rpm+ they run higher pressure as they struggle with volume but down at our revs its all about the torque.

Probably safer to not take much out of the exhaust port width. That piston has fatter rings and they just cant take the wear.
The top edge of the exhaust port will need work. They all do. Put some pictures up and I'll draw on them.
Molto Verboso
One or two fun scoots....nothing too precious
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Tue Jan 22, 2019 1:13 pm quote
I've never taken the time to understand what the 138/6 post TDC thing means, as I've always worked with degrees BTDC (open) and degrees ATDC (close). For low end grunt (touring), I choose max. 65 degrees ATDC for the inlet close and 115-120 degrees BTDC for the open = 180-185 duration. The open occurs earlier if you grind the rear of the inlet.

As Jack said, the 138/6 Mazz is racy. I used one in a BGM 177 build, and without any changes to the inlet (late PX150), I was seeing almost 75 degrees ATDC for the inlet close. Stock crank gives ~50, but can be as little as 45 on some motors.
Hooked
1984 PX(177)EFL
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Tue Jan 22, 2019 2:22 pm quote
Swa45, I'm a bit rusty on precise numbers, but the 136/6 you mention refers to the cut out on the crank relative to the bearing, which is 0 at TDC. So when combined with your Inlet pad location relative to TDC you get the total BTDC/ATDC dimension. As an example, when looking at cranks, I had this 'race' crank which I measured at 127/7, which, if I were to open my inlet pad to the max as intended, would still have given me insufficient BTDC and too much ATDC. So I also found the Mazz crank would give too high ATDC for what I wanted. I ended up cutting a standard crank to give 125/55. Here below, the 127 is the opening on the crank, the 7 is its location relative to bearing. Note to be careful whether the 7 is before or after the bearing, but when you combine it with pad measurements it gives you your BTDC/ATDC and/or any cuts needed to achieve it. Jack can do it in his head, but I did myself a little crank timing calculator for the job (C & D are Crank - D/C in your post, and A, B & E are inlet pad). I don't know if you needed that info, or if it helps or confuses, but I've written it out now, so might as well post it:

r mazz crank inlet timing.jpg
An example of where numbers fit

r calculator.jpg
Calculator



Last edited by sime66 on Tue Jan 22, 2019 10:40 pm; edited 1 time in total
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Tue Jan 22, 2019 3:22 pm quote
Thanks, Sime! I think that gives me more questions than answers, but it's also giving me enough fundamentals to start asking intelligent questions.

Also, for Jack, here's a picture of the exhaust port, looking up the barrel from the intake side. Any advice on porting it is appreciated

IMG_20190122_072133.jpg
Exhaust port, looking up the barrel through the transfer port opening in the piston skirt.

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
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Location: London UK
Tue Jan 22, 2019 7:46 pm quote
First thing is that exhaust port overall shape is more sporty than needed but it will be ok if we keep it lower.

Check the exact measurements from just inside the roof edge of the main transfer to the top of the cylinder. And the same for the exhaust. If you are to set the main transfers at 124 degrees then the exhaust will need to be 172 degrees at its centre.

For the exhaust port get a steel rule and see if there are any lumps in the exhaust port. From the bore edge to the exhaust stub should be as straight as possible. The sides of yours look like they funnel in. There should be enough metal in that cylinder to make it better. Remember where the stud holes are while shaping this.

The shape of the top edge should have a 20mm flat in the middle, as drawn. It might look flat now but when you check it it won't be.

img_20190122_072133_10158.jpg

Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
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Fri Jan 25, 2019 2:19 pm quote
I did a little theoretical measurement and it looks like I'll need to raise the top of the exhaust port 1.1mm. I won't be able to say for sure until I install the main bearings and can properly measure, though.

The exhaust definitely has some funneling. I had always assumed that was there for a bit of a venturi effect. I had wondered if it wasn't really for ease of mold removal, though. Cleaning that up will be easy enough.

It's supposed to be below zero (f) this weekend, so at least I don't have to worry about putting the bearings in the freezer to install them. I'm seeing myself setting up a temporary work area inside the house.
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Fri Jan 25, 2019 5:50 pm quote
chandlerman wrote:
It's supposed to be below zero (f) this weekend, so at least I don't have to worry about putting the bearings in the freezer to install them. I'm seeing myself setting up a temporary work area inside the house.
Ouch, and I thought working in the garage in the 50s was cold. I used to park my motorcycle in the kitchen. That wouldn't fly nowadays.
Molto Verboso
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Fri Jan 25, 2019 7:29 pm quote
Exhaust port up 1.10mm sounds about right. When moving it only worry about the centre. As this is a tourer not a racer the port doesn't need to be so big. Set the 20mm flat section at 172 degrees and blend the sides down to the existing port edge. Will end up looking more oval with a flat top centre.

Go easy on straightening out the port. Always be sure you know where the stud hole is and how much metal is left. If you use a 3/8 double cut rounded drum tool, it will get through it quicker.

I would guess the piston is not going to sit flush at TDC. The head might need work. Any thoughts? Or measurements so I can check?

I have to take my porting work inside during the Winter too. Which is exactly what I will be doing when I get home. I have a plan.
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05 Stella, '62 VBB, 76 Sprint V, 63 GL
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Location: Chicago. Well, Evanston, but that's almost Chicago
Fri Jan 25, 2019 8:21 pm quote
qascooter wrote:
ouch, and I thought working in the garage in the 50s was cold. I used to park my motorcycle in the kitchen. That wouldn't fly nowadays.
I've taken scooters inside to work on them, but it was because it was too hot for my tastes, not too cold.

I'm going to be left without adult supervision next weekend, so depending on where the forecast winds up, I might bring the Sprint's motor in for assembly.

My wife was actually more irritated that I put engine cases in the dishwasher than a whole scooter in the living room. Apparently, engine cases are not, in fact, "kind of like a dish."

Jack, I'll probably go ahead and mount the main bearings and get a proper measure on the port timings over the weekend. I have a good idea of what I'm going to be doing to the exhaust port, just need to sort out what sort of base packer I'll need to get those timings, plus hope that I don't need to have the head milled for squish or opened up for compression.

2013-07-16 19.13.23.jpg

2014-08-17 15.06.54.jpg

Molto Verboso
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Joined: 11 Jan 2006
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Fri Jan 25, 2019 8:29 pm quote
chandlerman wrote:
My wife was actually more irritated that I put engine cases in the dishwasher than a whole scooter in the living room. Apparently, engine cases are not, in fact, "kind of like a dish."
Oh man, I love this - what a crack up! I'll have to use that line "well honey, its kinda like a dish"...
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
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Location: Chicago. Well, Evanston, but that's almost Chicago
Sat Jan 26, 2019 1:01 pm quote
I installed the main bearings and dry-fit the crank and cylinder this morning.

To get to 124 degrees of port timing, I'd ideally have a 1.2mm base gasket. As it is, I'm going to use a 1 mm base gasket, which only gets me to 123 degrees. When I simulated that with a couple of sets of feeler gauges, I had a lip of 1.6mm between the crank at BDC and the bottom of the transfer ports.

Should I lower those ports to match BDC?

The to of the exhaust will also come up 1.1mm, then get flattened along the top, as recommended.

I'm also looking at probably needing to shave about .5mm or so off my head to get squish down to 1.2mm, but I'll wait until things are fully closed up for final measurements before I worry about that.

IMG_20190126_110113-marked.jpg
Lips!

IMG_20190126_141936-cropped.jpg
Exhaust port markup

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
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Location: London UK
Sat Jan 26, 2019 7:09 pm quote
Add a 0.2mm gasket to your 1.0mm and go for the 124TD. 123 on the mains will be 121 (or less) on the secondaries and this might make it slightly dull. Really need some dimensions so I can check what you're doing. Accuracy is important. The deck height of the piston and port measurements should be measured ten times to be sure.

Dropping the transfers to the new BDC is not as important as making a mess of it. If it was a racer it would matter slightly but for this tourer its not so important.

Use the piston to draw a line across the top of the exhaust port. Will help keep it all straight. Only focus on raising the middle 20mm and drop the edges down to where they are now. Do drop the exhaust port to the new BDC, this does matter on a Tourer.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Sat Feb 02, 2019 5:47 am quote
Jack221 wrote:
Use the piston to draw a line across the top of the exhaust port. Will help keep it all straight.
This was so obvious as soon as you said it, but it never occurred to me. Brilliant!
Jack221 wrote:
Only focus on raising the middle 20mm and drop the edges down to where they are now. Do drop the exhaust port to the new BDC, this does matter on a Tourer.
This is extremely helpful. It's the sort of subtle "knowing when to say when" that I can't thank you for enough, Jack!
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2036
Location: Chicago. Well, Evanston, but that's almost Chicago
Sat Feb 02, 2019 12:53 pm quote
Final re-re-re-re-re-measure for port timings and I'm sitting right at 124/170 with a 1.5mm base gasket.

I need to raise the top of the exhaust port by .5mm to get to 172, and I'll flatten it out at the same time.

The base of the exhast port comes down right at a mm to match the piston at BDC.

Time to hit the garage. I'm a lot more nervous about this than other porting work I've done. First time re-shaping ports in a cylinder.

Wish me luck!
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
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Location: London UK
Sat Feb 02, 2019 8:01 pm quote
I still find porting cylinders to be fascinating. Changing the size and shape of the ports, removing a little metal here and there and fixing the defects. When you're done, still looks pretty much the same but the power delivery is totally different. Hopefully not worse

How have you worked out your durations, vernier and maths or a degree wheel? A few degrees here and there doesn't sound like much but it really matters. Can you also give the duration for the secondary transfers and boost ports?
And don't forget to measure the exact stroke of your crank. It may be a 60mm crank but it won't be exactly 60.00mm but more like 59.85mm or 60.25. Need to be accurate for the best outcome. 124TD will go great, 125 or 126, on this, not so well.

A 1.5mm base packer puts it on track for a zero deck (or very close to what it was before) Might not need to touch the head. The compression will go up due to the crank and that may be enough.

Take your time on the exhaust port. Measure often, don't want to go over. It doesn't need to be pretty but it does need to be precise.
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