Setup 2007 Stella with DR177 DR 177, Sito +, 23 Tooth Clutch
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Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Sat Feb 01, 2020 6:35 am quote
jocco wrote:
swa45 wrote:
Most of the reading/research that I did several years ago suggested that a 60mm crank is not a good companion for the DR177 kit. Maybe try a 1.5mm head gasket instead, or 0.5mm base and 1.0mm head.
Thanks for the reply Swa45, I considered adding a thicker head gasket, but then what do I do about the squish?

I know some metal needs to be taken off either the head or the cylinder, but will this be wise to do, cause I dont think there is a lot of meat on either?
I think Jack is referring to removing material from under the cylinder by using a thinner packer of 0.5mm. This will lower your timing numbers and leave the top of the piston protruding above the top of the cylinder by 0.7mm if my math is correct. Giving you exhaust and transfer timings of around 168 / 122.

This should also lower your squish if it is as high as mine and others here, but still greater than 1.0mm with no gasket.

The top of the top ring in my kit is 3.2mm from the top of the piston, even with 0.7mm sticking out of the top, the top ring still isn't going to be above the top of the cylinder.
Hooked
Joined: 14 Jun 2016
Posts: 100
Location: Macedonia
Sun Feb 02, 2020 8:06 am quote
Wow, thanks for the all the help guys.

And thank you Christopher for clearing out a few things.
I never thought that its OK for the piston to be protruding a little from the cylinder, I always thought that was bad.

I can work with this new info now. will take new measurement tonight.

Nice job on on the porting Christopher, I think I went a little too far with opening the cylinder. Now I'm also considering cutting the piston so it fits the openings on the cylinder.
Also has anyone other then Geekspeed drilled a DR177 piston?

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First measurements

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went through :). lucky i used some JBWeld

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To cut, or not to cut the piston?

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Was thinking drilling a hole here on both sides

Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Sun Feb 02, 2020 9:47 am quote
It'll be interesting to see what someone says about cutting the side of the piston. Mine looks like yours but I didn't open up the piston opening, wasn't sure what that would do to the structural integrity. If I find out people are opening it up I'll open mine up.

My parts are sitting while I wait on my new piston rings, SIP was out, but rings are back in stock and shipped I hope.


If you do have some piston sticking up, make sure you measure the head squish band inner diameter, to make sure you have clearance for the piston. My squish band diameter is only 60mm ID. A 63mm piston will not fit into that spot. That is where you will need a head gasket with a 63mm or slightly larger ID to offset the 0.7mm you'll have protruding from the top. Make sure you fit the head gasket so it won't interfere with the piston with the play you'll have on the four studs.

Then that will get you back to having a larger squish band than you'll want most likely. Then you'll need to do like I did and take some material off the head.

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I have the calipers set at 63mm and you can see they are wider than the squish band area.

Hooked
Joined: 14 Jun 2016
Posts: 100
Location: Macedonia
Tue Feb 04, 2020 5:28 am quote
Did some measurements on the DR I'm working on.

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The squish is between 2.1mm and 2.22mm

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Looks like the piston will fit :)

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Got lucky. All I need now is to find some aluminium to cut a base gasket

Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Tue Feb 04, 2020 5:49 am quote
DR177 Cutting Side Skirt Opening Wider to Match Port
I never heard back from SWA on what his results were with cutting the side skirt to match the port opening in the projects forum. He may not have seen it, sent him a PM asking about it.

Your large squish measurements are similar to mine, removing 1mm will get you down to a better squish.
Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1247
Location: UK (South East)
Tue Feb 04, 2020 7:25 am quote
Oops, sorry I missed that PM. I used a Pinasco Magny Cours base gasket as a template to port the crankcase, then matched the DR cylinder base ie. I removed the 'shelf' on the other side of the gates. This resulted in the cylinder spigot windows opening up considerably to follow the shape of the transfers, so I matched the piston windows accordingly. Did this part make much difference to performance? Not sure. The kit served me well with a stock DR piston (modified), a set of Grand Sport rings and a Polini 177 head (tighter squish), but the engine now runs a BGM 177.
Hooked
P Series / Li / LML / Motobi
Joined: 24 Jun 2019
Posts: 137
Location: UK - 3rd Rock From the Sun
Tue Feb 04, 2020 9:44 am quote
Re: DR177 Cutting Side Skirt Opening Wider to Match Port
Christopher_55934 wrote:
I never heard back from SWA on what his results were with cutting the side skirt to match the port opening in the projects forum. He may not have seen it, sent him a PM asking about it.

Your large squish measurements are similar to mine, removing 1mm will get you down to a better squish.
I have cut many a piston on the skirt to get a good match, as long as you round the edges and corners you will be fine. as to drilling the piston, again i have done this many times in the past to allow some cool gases to wash over the cylinder wall - in line with the barrel studs - to reduce the risk of heat seizure.
Addicted
Honda elite
Joined: 19 Jun 2007
Posts: 755
Location: California
Tue Feb 04, 2020 10:11 am quote
Gravelrash2004 wrote:
Christopher_55934 wrote:
I never heard back from SWA on what his results were with cutting the side skirt to match the port opening in the projects forum. He may not have seen it, sent him a PM asking about it.

Your large squish measurements are similar to mine, removing 1mm will get you down to a better squish.
I have cut many a piston on the skirt to get a good match, as long as you round the edges and corners you will be fine. as to drilling the piston, again i have done this many times in the past to allow some cool gases to wash over the cylinder wall - in line with the barrel studs - to reduce the risk of heat seizure.
Interested to know more about this. My apologies in advance my intention is not to hyjack but learn more about adding a hole to the piston.

In my recent seizure I'm noticing two polished area's on the cylinder wall about the size of a US dime. Both spots are on each side of the exhaust on the stud path. In my case it looks like the piston seized on the clutch side exhaust stud. Is there more heat retention and less air cooling here? The seizure did not occur directly over the polish spot but next to it closer to exhaust port. The opposite side has no damage just a polish spot.

Was wondering if a hole on the clutch side stud path might be an option? Just one or both sides of exhaust?

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two dark area's on each side of exhaust port after 800 miles in line with cylinder studs

Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Tue Feb 04, 2020 2:13 pm quote
swa45 wrote:
Oops, sorry I missed that PM. I used a Pinasco Magny Cours base gasket as a template to port the crankcase, then matched the DR cylinder base ie. I removed the 'shelf' on the other side of the gates. This resulted in the cylinder spigot windows opening up considerably to follow the shape of the transfers, so I matched the piston windows accordingly. Did this part make much difference to performance? Not sure. The kit served me well with a stock DR piston (modified), a set of Grand Sport rings and a Polini 177 head (tighter squish), but the engine now runs a BGM 177.
Thank you for the update, I read your old projects thread and had a few ideas from that. With my LML case, I opened up the cylinder, to match the transfer ports in the LML case. The LML transfer ports with reeds, appear to be a lot larger than the Vespa PX transfer ports, from pictures I've seen. The only port I enlarged in the Stella case was the boost port or middle port by a few millimeters to match the DR177 boost port. My Stella case had a 23mm port and the DR177 cylinder had a 25 mm port. Going to open up the cylinder skirt also now, while I have it apart since others haven't had issues with it.

Going to keep my SI 20/20 carburetor for now, I have a venturi setup for it and would like to give that a try. I have seen mixed reviews about using a SI 24/24, and will save that for when I get bored, and want to see if it helps my setup with the way I use it. I'm mainly worried about highway riding at the moment. If I find I spend a lot of time at wide open throttle then I will give an SI 24 24 a try.
Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Tue Feb 04, 2020 3:01 pm quote
jocco wrote:
Did some measurements on the DR I'm working on.
I would be nervous about that tight of a fit. My cylinder head could move 0.3mm to one side when bolted to the cylinder. Iíd be tempted to use a rotary tool with a sanding drum and open that up a bit more. How much I have no idea without studying it for awhile.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2309
Location: Chicago. Well, Evanston, but that's almost Chicago
Tue Feb 04, 2020 3:53 pm quote
I've opened up DR pistons pretty extensively and never had a failure from it. I always open the port gates, then match the piston to those. I'll also add extra porting to the piston on a Malossi to allow additional cooling and that's never blown up on me (yet), either.

As noted above, just make sure the corners are rounded and you're not cutting into the reinforcing webs on the interior of the piston and you'll be fine.

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Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Tue Feb 04, 2020 5:16 pm quote
Pictures of Bottom Side of DR 177 Piston
This is what the bottom side of my piston looks like. Should I open it up or leave it?

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Looking at the area that would be coming off, kind of gives an idea of I go straight down.

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Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2309
Location: Chicago. Well, Evanston, but that's almost Chicago
Tue Feb 04, 2020 6:02 pm quote
I'd open it up.

I did similar work to the Polini on my SprintV here and on a DR here.
Hooked
P Series / Li / LML / Motobi
Joined: 24 Jun 2019
Posts: 137
Location: UK - 3rd Rock From the Sun
Thu Feb 06, 2020 4:45 am quote
O.P.
YES open it up. just make sure as mentioned above, it is smooth and rounded rounding off the sharp edges actually "adds" strength back to where the metal was removed



Hijacker
Was wondering if a hole on the clutch side stud path might be an option? Just one or both sides of exhaust?

Drill all sides of the piston in line with the studs - you can additionally notch an "x" into the hole to allow 2-stroke to "grab" in the grooves. a 2mm hole should be sufficient - then deburr and lightly countersink the hole (spinning a drill bit backwards by hand should be enough to clear and counter the hole
Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Wed Feb 12, 2020 4:18 pm quote
Rings Finally Came In
I have two sets of rings now, measured the ring end gaps in each set. The GS for a Polini piston end gap is 0.009" or 0.23 mm. The DR set is 0.10" or 0.25mm. Going to be installing the GS set, better looking finish and a tighter fit.
Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Wed Feb 12, 2020 4:33 pm quote
DRT Air Box Spacer and Hitting Frame.
What do I do with an air box cover that is hitting the frame, with a DRT spacer installed? If it didn't look terrible, I would adjust the box corner with a ball peen hammer. Might look better than trying to cut the corner off with a Dremel. Eventually I want to fit a venturi, after I get the air filter close.

Also a few pictures in case anyone is having trouble finding pictures.

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bodgemaster
1963 GL, 1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 5040
Location: So Cal
Wed Feb 12, 2020 6:54 pm quote
Depending on how much and where the airbox is hitting the frame, you may be able to resolve it by:

1. Replacing the rear engine rubber mount

2. Replacing the top rear shock mount

3. Using a longer rear shock spacer

Look at those before you start pounding on the airbox or the frame.
Ossessionato
Joined: 26 Oct 2015
Posts: 2079

Wed Feb 12, 2020 8:34 pm quote
Since it's just a Stella, take a hammer to it. Yes, a shock spacer will give you the extra clearance...until you hit a bump in the road. There's very little room to work in there in the first place, and that spacer will no doubt cause fouling out issues with the frame. Just make sure that you don't pound the frame into the shock spring. I'd at least remove the carb box before i started hammering away at it though. A rubber mallet would be leave less visible witness marks than a steel hammer though. If you do need that much clearance, i would just cut the sheetmetal then.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1668
Location: London UK
Wed Feb 12, 2020 11:43 pm quote
Why is keeping the stock filter so important?
Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Thu Feb 13, 2020 3:50 am quote
Jack221 wrote:
Why is keeping the stock filter so important?
I don't have to keep the stock air filter, I would eventually like to remove it in favor of a venturi or T5 air filter. That is why I was looking for ideas on how to fit a spacer for a bit more room. I'm under the impression there not a lot of room in there and a bit more room helps with the venturi and air flow.

Only keeping the stock air filter, until things warm up outside. That way I can get a few miles on her to make sure she running fine. Then go to a venturi up jet and start to dial her in better.
Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Mon Feb 17, 2020 5:11 pm quote
Would you grind a piston up like this?
Freaky sent me a few pictures of his pistons, this one is a DR piston. Would you grind around the pin like this? I'm hesitant to do it, I can't wrap my brain around grinding that center section down and moving that much more mixture. The transfer ports in a LML motor are pretty big. I opened up my piston skirt back to the web and stopped.

I'm basically to the point I'm going to put copper sealant on my parts and put it back together. Trying to decide whether to grind it or leave it.


Then I'm on to the clutch.

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Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1668
Location: London UK
Tue Feb 18, 2020 12:20 am quote
If you can be bothered yes but lots of other parts have to be adjusted well for it to make any noticable difference.
Hooked
Joined: 14 Jun 2016
Posts: 100
Location: Macedonia
Wed Feb 19, 2020 4:20 pm quote
Wow, nice pics you got there Christopher.
I was planning to do something similar to the DR Iím working on, this piston is still less grinded around the pun then a stock malossi 166 piston.
Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Sun Feb 23, 2020 1:52 pm quote
It lives
Put the top end back on, wanted to see if she would start. Started up with a Little choke and seems to run fine again.

Now to figure out how to upload a video of link to youtube.


https://youtu.be/rGBErf3kzzs





https://youtu.be/rGBErf3kzzs


Checked the cranking compression and it's 148 psi, I was told something around 140 psi is good for pump gas. Not sure if that will go up as the rings seat themselves with use. Top end fit isn't as tight as it could be either, the ring end gap is well within tolerance, but not so tight that I had to take anything off a new set of rings. The side gap for the piston to cylinder wall is also on the medium side. It does rev better to 5500 rpm with the 1mm base plate spacer and ported exhaust port. Didn't want to rev it to much with new rings until they seat.

Next up is going to be the clutch, I have a DRT 23 tooth gear to install. I know it should be to high of a gear, but it works on a Stella Fireball with a factory 150 cylinder. I Want to see why it grabs figure if I need parts I want to get them on order while it is still cold here. Once it warms up I want to be ready for tuning and riding.
Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 218
Location: Rochester, Minnesota
Mon Feb 24, 2020 5:46 am quote
My list of changes so far
To help me keep track, of changes I've done so far, will add to as I go along.

The day I test drove it and brought it home it was cold below freezing. I rode it wide open in 4th and couldn't get over 50 MPH or 80 KPH.

Boyesen Reeds
Cut the center support out of the reed block
Blended the parts in the carburetor reed block stack to flow better
55/160 Idle Jet 160, Be3, 110 main jet
Drilled heart in air filter
Cleaned up carburetor, installed new gaskets, drilled hole from fuel bowl to main jet to 2.0 MM and blew out all openings with compressed air.

Started and ran on center stand at this point, to cold and snow on the ground didn't do anything else. Since it still seemed to run fine on the stand I moved on to other projects

Opened up the DR cylinder base, two large ports on the side to match the LML case openings.
Opened up the LML third small port in the case from 20 mm to 25 mm to match DR cylinder.
Cleaned up exhaust port and moved it up 0.50 mm, on accident mostly just material removed to clean up casting around port.
Reduced squish from 2.77+ mm to what should be 1 MM by removing material from head. With the shape of the DR head it is hard to measure squish, with no real squish band.
Installed a 1.0 mm base gasket to set squish at 1.00 mm and increasing port timings.

Started and ran on center stand at this point, to cold and snow on the ground still, didn't do anything else. Since it still seemed to run fine on the stand I'm moving on to the clutch.

I have a 23 tooth gear the same as the Stella Fireball mentioned earlier in this post, to install while inspecting what I have for a clutch.

TO do at some point:

I have a kytronix waiting to be installed.

I would like to establish Top Dead Center and timing marks and install a Kytronik. Looks like I can install it set it to "0" initially make sure it works and set it to a conservative 6į. I like the idea if having a timing curve the same as vehicles have had since the early 1900's. After I get things dialed in better I can push the limits more on the timing, I figure a conservative something should e better than nothing.

https://www.kytronik.com/collections/kytronik/products/smart-booster2016-2

Last edited by Christopher_55934 on Mon Feb 24, 2020 8:03 am; edited 2 times in total
Addicted
Honda elite
Joined: 19 Jun 2007
Posts: 755
Location: California
Mon Feb 24, 2020 6:48 am quote
When the snow melts try doing some WOT tests in 2nd gear. Get a large main jet and find the point where it's too rich, find that first. It will be sputtery but clear out if it's still too lean when it's sputtery up into the high rev then you can stop and begin working back down. The main jet and since you have drilled the supply to 2mm has an effect on fuel supply to the pilot and you'll start dialing that in. The atomiser can be dialed for the transition from pilot to main. Also plug chops will help.

Yesterday I read something on adjusting the air fuel screw on the let's talk atomiser thread. I found this very useful: copied and pasted from jamesjohn 6/20/2013

To set the mixture screw correctly, here's what you need to do :

Start the scooter and go for a 1-2km run to warm the engine up.

1. With the engine running on the stand, take the engine side panel off. Turn the idle speed right up, the long screw with the flathead screwdriver fitting that pokes out of the carb box top, turn clockwise in.

The engine will be racing now!

2. Immediately turn the mixture screw on the back of the carb all the way in, the engine will get choppy and the idle will drop. On PX200 models it will require an 7mm spanner, there's not much room in there.

3. Immediately then turn out the mixture screw from closed in 1/4 turn increments, the idle will increase and the engine will start to smooth out. Take a few seconds wait between each 1/4 turn out. Count the number of turns as you open the fuel screw out.

4. You'll get to a point where the the engine will have smoothed out and the idle stops increasing when you turn out the mixture screw. This is close to where it should be set.

5. Adjust the idle speed back down to an acceptable running level. Then listen to your engine when you blip the throttle.

6. If the engine 'bogs' and feels flat when you blip the throttle it is probably set too rich. If the engine 'hunts' and takes more than 2 seconds to come back to a steady idle after blipping the throttle, it is probably too lean. A lean idle that 'hunts' the revs will make a 'pip, pip, pip sound.'

You should be able to blip the throttle, the engine should rev. clean and it shouldn't either bog, or 'hunt out the setting'. It should rev. and return to a good idle within 1-2 seconds.

7. Make a small adjustment here if neccessary. Then adjust the idle speed slightly.

8. On tuned Vespas, if it takes more than 4 complete turns, then pop in a richer idle jet, and repeat. This is the smaller jet on the left. The PX200 runs a standard 160/55 idle jet. The T5 runs a richer 100/50. The richness of the idle jet is the ratio of the two numbers, the lower the number, the richer the idle jet. The 100/50 is 2.0, the 160/55 is 2.9. The 100/50 is therefore richer.

If it takes less than 2 turns on a tuned Vespa, consider popping in a leaner idle jet and repeat.
Ossessionato
Joined: 26 Oct 2015
Posts: 2079

Mon Feb 24, 2020 11:16 am quote
That 23 tooth clutch will be just fine in 1st through 3rd gear, but in 4th, your power is going to drop off big time...unless you have a slight downhill and tailwind. Just because the Fireball came with an upgear, doesnít mean it was a good thing. Iíve played around a bunch with 21, 22, and 23T gears before, and if youíre one tooth off, it makes a whole world of difference. I personally think a 22 tooth would be spot on for your build.
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