Vintage vespa with sidecar
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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: 7646
Location: Victoria, Australia
Fri Jun 19, 2020 12:10 am quote
I'm glad you wrote "FROM GREECE", otherwise I was in danger of passing out.

I like your 'timing vane', a very good idea! It's always a bit vague as you say. I come back in a year's time and all the marks seem to be gone.
Now all you need to do is make from a solid block of aluminum with 1 degree marks, supply it with special bolts in cute packaging and sell it a la Crazy Monkey - the Vain Vulture. Only 53 euro.
Style Maven
74 50s x3 78 P200 84 Cosa PK50XL2 58 AllState 68 Sprint 80 50special '66(?) Super125
Joined: 22 Nov 2010
Posts: 7754
Location: seattle/athens
Fri Jun 19, 2020 1:25 am quote
SoCalGuy wrote:
I’m not sure a dial indicator is necessarily the most accurate way to find true TDC.

I think the piston stop method might be equally if not more accurate as it completely eliminates dwell of the crank. Especially if you use a large degree wheel and a pointer that can be set with precision.

...
+1, this is how I do it and it is easy and reliable. With a dial gauge you can still rotate the crank a bit with practically no movement of the gauge it seems. Some judgement required...

Probably redundant, but:

You can make a piston stop from an old spark plug by welding or JBWelding a short extension in it, now you can screw it in then rotate the crank all the way CW and mark where it stops, now rotate CCW til it stops and mark that. Now split the difference between the marks and that is TDC. Unambiguous for me.
Hooked
Bodgerific 150 Super, 50s in progress
Joined: 18 Aug 2016
Posts: 291
Location: Melbourne, Way Downunder
Fri Jun 19, 2020 4:27 am quote
I'm plus one for this piston stop also.

Last time I had the engine on the stand I added a laser level to the mix. Takes the pointer/angle problem right out of the mix.
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Fri Jun 19, 2020 6:51 am quote
Let's hope 1.5 degrees and weaker jetting is enough. If it's still doing it might need a bit more retard. Can't be sure without normal plug colour.

Liking the timing vane. Plug thread on the dial gauge us a novel idea too. Checking with piston stop, dial gauge and buzzwangle, all together is not too much. Use all u have. Unfortunate the Vape doesn't have an off switch, like the Kytronic does. Makes setting static timing easier. If you are happy with the strobe check revving 6000rpm at 19, then that's done. And now you're sure where it is.
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Fri Jun 19, 2020 7:24 am quote
Nothing like screwing something up to learn how to do it better.
Perhaps if I pull out a "how to upgrade your cylinder" thread I can quote you guys on some of the favorites posted. Good stuff.

Voodoo - I have a piston stop - but the rod has just enough flex that it brings a bit of "feel" in two the process. Your spark plug home made one with a rigid extension is a good one. Makes mine seam complicated!

Craig - King of the speciality tools and dirigible quality engine sealing - I am still trying to get my head around exactly how you put a laser level to use! Imagining dim garage, lab coat, reflections of lasers off glowing triumph and some form of steam punk goggles.

Ginch - the CM Timing Vane™ (of course) as seen on TV can be purchased for just $19.95. (Some assembly required). Funny - I looked for an old power tool that I could strip of its degree reading plate - but settled for my ugly hand cut vane 'cause I ran out of patience. When engine is off next time tho...

Jack - yup. triple back flip salchow timing deep dive left me with A. a very accurate means to measure & B. pretty damn close to where I had the Polini (and the BGM detonation). But now we know and I can adjust in fine increments - and will be able to fine tune in.

Ok - get some riding in today - take a quick look at the piston to ensure I'm not frying it - and perhaps a speed run before days done to see how things are shaping up. Time to order some sanding drums.

Thanks all!
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Fri Jun 19, 2020 3:41 pm quote
We interrupt the regularity schedule programing to get some opinions on which P200 cases I should choose.

What's that you say?
CM - P200 cases?
Whodat is waving is hand held fan up under his collar to dissipate the rising heat.

Yep - for the future - but picking up now - cause they are coming to me with some good will. Just have to choose which ones!

What door should I choose?!

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Door #1 - good rotary pad - fu-barred case stud.

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#1 rotary pad

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Door #2 - cases look fine - rotary pad has some stuff melted to it

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Door #3 - swamp thing.

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Door #3 swamp thing's rotary pad

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Door #4 - pad in decent shape - cases seam in good shape.

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Door #4 oil feed hole has been epoxied shut

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Door #5 - cases are clean

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Door #5 rotary pad is in nice shape. But... case numbers don't match!

Addicted
bare metal cafe racer
Joined: 01 Sep 2017
Posts: 775
Location: Aotearoa (New Zealand)
Fri Jun 19, 2020 3:48 pm quote
‘Bout bloody time!

No idea which to choose. But thinking that is a epic stash in the USA?
Moderator
P200 PX150
Joined: 28 May 2008
Posts: 4262
Location: Hustletown, TX
Fri Jun 19, 2020 6:01 pm quote
5 options?!?

I had to do backflips for a half case... Damn man buy a lottery ticket.

____________

#1
or #5
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Fri Jun 19, 2020 6:26 pm quote
In the USA.
Favor for a friend - this is my pay off.
I get to choose one.
Btw - non matched cases had only 1100 miles on them. Suspect dealership replaced half case at new.

1. Does anyone truly know if u matched cases are a problem or is that hear say?
2. What is the value of a set of stripped cases?

Thanks.
Keep playing!

* edit
Quote:
I had to do backflips for a half case... Damn man buy a lottery ticket.
Clean livin
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Fri Jun 19, 2020 10:16 pm quote
The only point of building a 200 would be that it goes significantly better than a 187. Something around 30bhp. For this it will need to be reed valve, so rotary pad doesn't matter. Avoid water damage and any stripped threads. Unmatched cases can be fine, just check the base is flat, with no noticeable step.
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sat Jun 20, 2020 9:13 am quote
Houston... we're screwed
Ok.
Thanks for the phone a friend advice on cases.
Jack - assume there are some trade offs if I go reed?
In any event - this was intended for a future project.

Now - about that problem.
Some sad news from the fly side seal.
Was good as recently as last week.
Appears to be good old fashioned worn-out.
How can that be with modern rubber components after just ~1500 miles?
No diving saves possible here that I am aware of - just have to bite the bullet and split the cases I suppose.

Shame - was just about to test the BGM for power.

IMG_6249.JPG

Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Sat Jun 20, 2020 12:02 pm quote
If that's the one patched up with fibre glass, it didn't do so bad.

2 hour job in the frame. Just saying.
Hooked
Joined: 22 Jul 2018
Posts: 106

Sat Jun 20, 2020 2:58 pm quote
Why are you going to split the cases to change a fly side seal? Hook it out and push a new one in.
bodgemaster
1963 GL, 1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 5299
Location: So Cal
Sat Jun 20, 2020 3:35 pm quote
BlackT5 wrote:
Why are you going to split the cases to change a fly side seal? Hook it out and push a new one in.
Flyside seal on a VBB has a metal flange and gets tapped in from inside the case.

16096D3C-3E75-4E10-8D6A-5521211BAADE.jpeg

Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sat Jun 20, 2020 5:52 pm quote
Quote:
If that's the one patched up with fibre glass, it didn't do so bad. 2 hour job in the frame. Just saying.
This was a new seal when I put in the crank shaft - 1200ish miles ago.
Really surprised it failed.
Spliting cases is a chore - with stripped studs and the like, a risk.

So - I decided to make a seal myself that was inserted from the outside...
Drying now.
Speed test in the AM.
🙂

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The seal that was on there is one of these. It has a small rubber part cast in the center.

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Grabbed a couple of these - they have a standard seal pressed in to a metal cup - so I was able to pry the seal out to use it.

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The offending seal

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Used a sharp point Dremel and carved a 360 hole. Got a little dusty... but used a wet vac and managed to get it cleaned up nicely.

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Went in with a mini sanding drum and cleaned it back to the edge - leaving a taper - the sanded metal you see is the old seal cup which remained.

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Pressed in the new seal and checked for pressure. Tight as a drum.

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To add some security to the seal - I coated the perimeter with motoseal

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Then fit a washer over it - that I tapered so the Stator would hold it centered in place and create a retainer for the seal

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Put stator on and tightened it down - just a touch of interference with the washer so it is held tight

CM's Bodgery Meter.jpg
CM's Bodgery Meter.
(Yeah - I know...)

Ossessionato
Joined: 26 Oct 2015
Posts: 2505

Sat Jun 20, 2020 6:10 pm quote
Jack221 wrote:
The only point of building a 200 would be that it goes significantly better than a 187. Something around 30bhp. For this it will need to be reed valve, so rotary pad doesn't matter. Avoid water damage and any stripped threads. Unmatched cases can be fine, just check the base is flat, with no noticeable step.
I agree with everything jack said.
Hooked
Joined: 22 Jul 2018
Posts: 106

Sat Jun 20, 2020 7:40 pm quote
SoCalGuy wrote:
BlackT5 wrote:
Why are you going to split the cases to change a fly side seal? Hook it out and push a new one in.
Flyside seal on a VBB has a metal flange and gets tapped in from inside the case.
Shit, my bad. I thought this was a later motor.
bodgemaster
1963 GL, 1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 5299
Location: So Cal
Sat Jun 20, 2020 7:56 pm quote
Damn. I think that deserves “Voodoo practical”.

Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sat Jun 20, 2020 8:19 pm quote
BT5 - good to have you along - and thanks for jumping in.
Yup - older cases that normally have the seal inserted from inside.

"We have this fabulous motor, that is also a swing arm!, and its very simple, so we are going to put 2 of the 8 serviceable parts on from the inside - so the whole damn thing has to be stripped down to refurbish them!" "Tutto Bene!"

SoCal - thanks! Actually - the Bodge O meter is somewhat misleading. Make Planet Vespa Blush is actually closer to Voodoo Practical than Chandlerman's pearls - cause its a circle. You have to use a timing wheel to read it.

Working on getting the "bring that guy along on the ride to fix shit on the side of the road" invite- which you currently hold the title for...



-CM
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Sat Jun 20, 2020 10:14 pm quote
Top work. Full on bodge but elegant. Was possibly only 30 minutes short of splitting the case but hey. If it only lasts 1000 miles you can do it again.

So, any time for a test run?
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sat Jun 20, 2020 11:46 pm quote
Quote:
So, any time for a test run?
Ha! - no - allowing to cure.
Upside: My cases now have a serviceable fly side seal.
I was just hell bent on not splitting the cases if I didnt have to.

Timing should be set now - but good moment to jump back to that discussion and ask a question.

My understanding:
SoCals' motor was hiding the heat in the exhaust port as it was too retarded.
As you add advance, it moves the heat to the head and away from the exhaust.
But I have seen other's who are advancing timing to take heat down/ diminish pinging.

So if I have it right - advancing the timing will often lower temps - but if you are way retarded to start with - it may initially raise the measured temps as it is moving the heat our of the exhaust and into the head.

Have I got that right?

Speed runs tomorrow on the newly improved fly side seal.
Then we have to start thinking about how we are going to set up the BGM for its performance version.
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Sun Jun 21, 2020 5:36 am quote
Seal really just started leaking then. What part failed?

Timing is not so simple. Lots of guys simplify it by setting it as instructed and leaving it there. If the instructions say 18, then it's set at 18 and that's it. Understanding why and what affects it could mean more power or better reliability. Since more of us use variable timing, it is now less scary and we experiment a lot more.
There are so many variables I'm not going to try and explain them all (any). However, the idea on a 2 stroke is that the most reliable timing , is as advanced as possible without detonation or overheating. Sounds easy but usually gets expensive.
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sun Jun 21, 2020 7:38 am quote
No parts failed.
Caught the leak quickly on this one and never saw over 300° - new something was amiss when I saw temps creeping up.;
It's as if you didn't even read my last post.
🙂
Quote:
the idea on a 2 stroke is that the most reliable timing , is as advanced as possible without detonation or overheating
Ok - but clarify for the crowd (me being the crowd) - cause there is some confusion.
by "As much advance as possible" I assume you mean at high RPM. (You aren't going to get overheating and detonation at idle). Do you mean as much retard as possible?

Variable timing systems retard the ignition as you rev up the motor.
They provide you with more advance at low RPM - less advance at high RPM.
e.g. you might be at 25° at idle (more advance), and 18° at high RPM (less advance).

Isn't it the lower the number BTDC, the more power/aggressive it is, but the more retarded you are setting it?

Singed - almost-have-this-untangled -but-need-your-help
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Sun Jun 21, 2020 8:27 am quote
Just speed read it again. Didn't see the bit about where the leak was. Rubber to crank? Rubber to plate, plate to case?

Advance is how far BTDC it fires. The earlier that is, the more Powerful. Higher degrees is better. This is at any rpm. And why variable is so much better. A typical advance on a four stroke goes the opposite way and advances more as it revs higher, ending up at maybe 38 degrees BTDC. This is going to confuse. A two stroke has to go the other way as it only has half a stroke to cool the piston crown, whereas a four stroke has 3 half strokes to cool. Big difference. Lots of ways to use that to our advantage.
bodgemaster
1963 GL, 1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 5299
Location: So Cal
Sun Jun 21, 2020 9:01 am quote
Let me throw this out ...

I don’t think it’s a question of timing being be as advanced (or retarded) “as possible”.

Ideally timing should be correct for the engine speed (and load).

Think of it as hitting a baseball.

If every pitch was the same speed, you wouldn’t have to adjust your swing. Swing too late or too early you’re going to foul it off.

If an engine did nothing but idle, timing wouldn't have to advance or retard. The problem is engine speed and load is always changing. At higher revs, the piston is moving toward the head faster so the spark needs to happen a bit later - i.e., closer to TDC - for the compressed mix to combust at the right time.

So we either pick a reasonable static timing that will work over a range of speeds, or we use a variable timing system that adjusts as rpms change.

But - back to the baseball analogy - regardless of which you use, you still have to find the timing that will allow you to hit the pitch squarely at some given engine speed. And like Jack said earlier, I think that is a combination of experience and trial and error.
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Sun Jun 21, 2020 9:34 am quote
Get what you are saying but that is the reality of two stroke. As the rpm increases the timing needs to fire later, closer to TDC. However, this is not because it goes better but because it would overheat if it didn't. If heat was no concern timing at 38 BTDC, at max rpm would make the most power. As it does matter, to have this as big as doesn't overheat, is as far as we can go. The more highly tuned the less by it can take. A highly tuned 12000 rpm two stroke bike might have timing at 8 degrees at max.
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sun Jun 21, 2020 9:55 am quote
Well - I am getting an education on this one.

My prior thinking.
- Variable retards so that it get's more power the less BTDC it goes - but out makes it hotter so there is a limit to how low BTDC you can take it.
- Jack's "19° at 6K RPM" seemed so aggressive - because that meant it would be retarding to about 15° at 9K RPM and would surely overheat when I held at WOT.
- The Polini was even more retarded by about 2° and I thought that meant I was being crazy aggressive - not less aggressive - with timing - previously.

Now I am looking at it differently:
- The adjustments I made to timing (advanced about 2°+ from Polini) are making it more aggressive, not less.
- I may get more power from this - but I am also likely to see more heat (which I am).
- As we tune these cylinders - I want to get as advanced (higher BTDC) as I can without over-heating - to max out power?
- At the other end of the scale - if you retard timing too much to fight off heat - you just move the heat to the exhaust port - which is not good as it exposes side of piston and rings to super hot temps as it passes the port.

Have I got this thing?


BTW - Jack -kidding aside - The failure of the seal was rubber to crank. I was surprised. not much more than 1000 miles - of all things - the rubber wore out? Corteco seal looks pretty in blue - but should not have failed. Was not dry, and crank is new and unmarked. Part of the reason I didn't just split cases was - I want a serviceable solution for that seal. Now its a 20 minute job. Maybe I will upgrade to DRT's fancy version when I split - but this is what I had at hand.
Hooked
Joined: 22 Jul 2018
Posts: 106

Sun Jun 21, 2020 11:25 am quote
You got it right on timing. It's a fine compromise that has to be made.

I got a solution to your seal problems. Build the P2 motor and all seals are externally swapable. See? Problem solved.
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Sun Jun 21, 2020 12:08 pm quote
Yeah, the looking at it differently is correct. Now, to expand on BlackT5, it is a balance. What we are actually aiming at is, the least advance that gives the most power. And doesn't detonate.

With the seal, I doubt those VBB cases were designed for 8000+ rpm. Does the fly seal have an oil way, like on the PX?
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sun Jun 21, 2020 1:52 pm quote
Ok.
Im clear on timing game.
- Minimal amount of advance that maximizes power.
- Pinging means too much advance or too lean jetting. If jetting looks good - retard timing a bit.
- Currently at 23° at ~1000RPM idle (give or take...). That means it advances to almost 26 degrees up at 4000 RPM, then it retards to about (-5.5 from 23°) 17.5° at 8500 RPM - which seems to be max RPM as cylinder is currently set.
- I have leaned it another step to EQ31. There is more power and it is running quite well. Smart Carb doing its job of being quick to jet in.
- Temps are higher than they were in the Polini by perhaps 20°, and quicker to heat up to low 200's (which is ok). I could back off the advance a hair on this if I find any pinging or too much heat.

Observations now that I am in the ballpark on jetting and timing.
1. BGM is smooth and broadly powerful.
2. Timings give peak HP all in by about 6800 RPM and max RPM is 8500
3. HP is probably 1-2 fewer than Polini - which had higher timings and was opened up. Expect to match or better with mods to the exhaust port.

It is often said, when it comes to jetting - every motor is different.
In this case - the cylinder and head are different - and the jetting needs to be set two notches leaner on the Smart Carb.

Jack(or others) - knowing what you know about the two cylinders - Polini and BGM - what do you attribute the need for leaner jetting on the BGM to mean/ be due to?

Displacement =
Compression - BGM is slightly higher
Spark plug placement =
Squish design = similar shape, BGM is at .8, Polini was at 1.0

All other things held equal.

Edit: fly side seal on VBB cases has an oil passage. Apparently I was so excited by how well my fix was going that I forgot to check if that had become clogged... My mind wondered the same thing - before it wandered as it does...

Screen Shot 2020-06-21 at 2.32.55 PM.png
BGM EQ31

Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sun Jun 21, 2020 2:01 pm quote
Reference: Polini. high 16's to low 17's in HP. North of 9 in torque.

screen_shot_2020_04_14_at_83535_pm_13478.png

Addicted
bare metal cafe racer
Joined: 01 Sep 2017
Posts: 775
Location: Aotearoa (New Zealand)
Sun Jun 21, 2020 6:24 pm quote
Question - with a variable/sport VAPE - how important idle speed?

If timing is set based on actual riding rpms (I think mine is set so max advance will be -17, but mid range -21: I asked for safe and sedate to begin with). But that means it will likely idle somewhere around -17 also?

Just checking that I'm not potentially causing damage simply because of where I set my idle speed. I know there were report of "holed pistons" while idling in another post (that was in turn debated).

Thinking I should get a static CDI (worth having a backup anyway it sounds like). And a timing light.
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sun Jun 21, 2020 6:58 pm quote
Working through all this myself right now - but here are my thoughts on the matter.
1. You aren't going to just hole your piston idling. There would be detonation/ hot spot damage well before hand. My take would be - shove a camera down there and have a look - benchmark it - and keep an eye for the first 100 miles or so regularly.
2. If you look at the vape timing - max advance is dependent on max RPM - it just keeps going. If your motor max RPM is 8K, and that was 17°BTDC, and your idle was at 1000 RPM - you would be at about 22BTDC at idle.

That seems pretty reasonable if that is how they have it set.
Since you have big tires on there - my recommendation:
- figure out what your RPM is at common cruising speeds.
- Keep an eye on temps there. It won't be an issue at WOT - you will be plenty retarded. But if your cruising at 4K RPM - that will be where it is most advanced - so pay attention to temps and see how it looks. IF they are good - you should be good.
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: 7646
Location: Victoria, Australia
Sun Jun 21, 2020 7:08 pm quote
I've had my Vape for maybe 18 months now and no trouble. That may be because I have a spare CDI.
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sun Jun 21, 2020 7:30 pm quote
Well - since we are on the topic...
I could use some insights myself.

I am chasing a heat issue.
The BGM climbs to 300 if I try and cruise at 50-52MPH.
That's somewhere close to 6K RPM.
I shut down at that point - this is 1/2 throttle area.
Polini would have been 30 degrees cooler and more stable.

I have re-checked for air leaks - all good there.
I have crept the timing down (retarded) a few degrees at a time.
Currently my thinking with the VAPE is - you have to set timing based on either target RPM - like 6000, OR you have to set it at a max advance.

The vape advances up to 4K RPM - so shooting a light at it as you accelerate to identify that timing ° tells you all you need to know about idle and high RPM.
Also - I find that it jumps around A LOT at idle - so trying to determine what exactly the timing is at 1000 RPM seems fruitless to me.

In any event - don't like the high temps and unclear what's causing.
More sleuthing work needed perhaps.
Thoughts on where I might look?
Addicted
bare metal cafe racer
Joined: 01 Sep 2017
Posts: 775
Location: Aotearoa (New Zealand)
Sun Jun 21, 2020 7:57 pm quote
Ginch wrote:
I've had my Vape for maybe 18 months now and no trouble. That may be because I have a spare CDI.
Murphy's Law of CDIs... I'm hearing you.

Probably applies to cables as well.
Addicted
bare metal cafe racer
Joined: 01 Sep 2017
Posts: 775
Location: Aotearoa (New Zealand)
Sun Jun 21, 2020 9:26 pm quote
So... finding the advanced/retarded nomenclature very hard to follow. But then I'm an advanced retard, so hey... But hoping to summarise to see if I'm keeping up...

Static timing: generally somewhere around 21deg BTDC
https://beedspeed.com/pages/vespa-standard-ignition-timing

Variable: Advances the spark so even further from TDC, or retards it so it is closer to TDC. Mostly advances because thats where the money is - when racing, at high rpm.

Basic aim: Start the fuel/air burning before TDC, so it all goes boom at the right time delivering maximum power on the down stroke, and all burnt before too long so none wasted (and still burning on the way out, which would raise exhaust temperature too much/in the wrong way).

With higher RPM, need to advance the timing because the time to reach TDC will be shorter - so need more time to ignite it all before TDC (not sure about this b/c SoCal suggested the opposite???)

Igniting it too soon will mean the boom might happen before TDC... pinking, pinging, knocking... or the dreaded detonation.

And then there is a whole lot of detail regarding exhaust temperature/trapping ratios that I don't understand - but is totally important for 2 stroke performance.

And likely the best way to actually sort the timing is by sorting the jetting first, and then using a dyno? Because this will bring all the crazy aftermarket cylinders, pistons, cranks, dremmel work, exhaust systems together so you can use the goldilocks principal of "just right".

But you need the jetting sorted first because this determines the air/fuel ratio - therefore burn-speed, therefore absolutely relevant to timing. And you don't want to be trying to sort bad jetting with timing, because timing is like the cherry on top - brings all the elements together. But if the cake is shit - the cherry won't make it better.

Something like this?
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Sun Jun 21, 2020 10:26 pm quote
pheasant plucker wrote:
Igniting it too soon will mean the boom might happen before TDC... pinking, pinging, knocking... or the dreaded detonation.

But you need the jetting sorted first because this determines the air/fuel ratio - therefore burn-speed, therefore absolutely relevant to timing. And you don't want to be trying to sort bad jetting with timing, because timing is like the cherry on top - brings all the elements together. But if the cake is shit - the cherry won't make it better.

Something like this?
This explains it better than I did. The boom is not actually a boom but a burn. Officially called deflagration. Takes about 40 degrees to go boom but if you start later or way too rich, it takes a bit longer. Burning while still going out the exhaust port always ends badly.
Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Sun Jun 21, 2020 10:40 pm quote
Based on PPs cherry on the cake, if you are happy with the jetting and sure it's not rich, reduce the timing until it's holding about 280F at mid cruise. Don't worry what the numbers are, just keep going down a degree at a time. Wouldn't be surprised if power goes up.

The BGM is running weaker jetting because it's less powerful than the Polini at the moment. Transfer timing is similar but exhaust is lower (very low aka tug boat). If you do copy the Sime66 porting the BGM will go way better.
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1395
Location: california
Sun Jun 21, 2020 11:18 pm quote
To ensure we are all speaking the same language.
The higher the number BTDC, the more advanced.
The lower - the more retarded.
e.g. 24 is more advanced than 19.
Quote:
Variable: Advances the spark so even further from TDC, or retards it so it is closer to TDC. Mostly advances because thats where the money is - when racing, at high rpm.
Not quite.
With the Vape - from idle to 4K - the timing advances.
4KRPM is max advance, not 8K RPM for example.
From 4K to infinity - it actually retards.
So I would disagree - tho respectfully as it has taken me some time to digest.

By way of example, at 5200RPM - it is the same timing as 1000 RPM (around which your idle is set).
At the higher RPM - timing is well retarded on a steep curve.
So if you set your idle at 1000RPM, it advances until 4K RPM, then falls precipitously.
By 8K RPM, it is retarded by 5 degrees - not advanced.
Quote:
With higher RPM, need to advance the timing because the time to reach TDC will be shorter - so need more time to ignite it all before TDC (not sure about this b/c SoCal suggested the opposite???)
While the logic makes sense - that is not how it works.
At higher RPM - your system is retarding as noted above.
Chart below shows it.
Assume you set your idle at 1000 RPM.
You can then see - it advances from that mark until 4K RPM - then retards - past that mark - and continues to retard further as your revs increase.

Its for this reason - that I recommend shooting your timing light and slowly raising the engine RPM - until you see it move to its most advanced point.
Its very stable at this transition point - unlike idle level RPMs
Once you know the max advance ° - you can calculate all other timings for all other RPM.
When you get your gun - you will see what I mean.
From a practical sense - I think this is the best way to set timing with the Vape.

Jack - good thought on retarding the timing to kill temp. Would have proceeded but have SoCal's burned rings stuck in my head from what happens when you get too retarded. (this discussion is ripe with opportunity).
That said - agreed. If temp remains stubborn - will assume that I have some form of leak that is not showing itself with bench testing and carb taken off.
Leak test when static is impeccable - so if so - it's a mystery.
Otherwise - the continued retarding should get my temps under control and I have just not reached the point yet.

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