Modern Vespa

My factory markings were off by something like 6 degrees when I checked them. I used a piston stop and digital angle finder to verify "0" or TDC. Then marked the timing marks with the digital angle finder. I have a different factory style stator plate and flywheel. Parts mixed between a P and PX.

Are you still running an EGT, I don't see any mention of EGT readings. I'm waiting on mine, might not be able to use it this year depending on weather.

Nice to see you back at it. What's the jetting now? Vortex still on?

Yes i am still running an EGT, but on that 10 min city driving run it was not enough to register on the EGT gauge. 800F minimum gauge for exhaust temps. Before, I believe the temps were focused more on the cylinder/exhaust and less on the piston due to such advanced timings.. now its focused more on the piston and less on the exhaust so the piston gets hotter faster. My guess is this means I will need to go up slightly on MJ to keep piston temps down at WOT, and adjust idle jet to suit those changes. Timing will stay until i see issues with either the EGT or CHT once jetting sorted again. Current timing is 23-19 (idle-7000rpm).

My timings were pretty far off originally from the marks I made on the case next to flywheel. I'd say 23-19 is about a quarter of an inch difference on those marks.. and when I ran it to 7000 to check with gun, it was about a quarter to half an inch beyond my 19degree mark which means it was probably around 15-14 degrees at 7000 rpm. This is why it seized on highway.

Hoping now that its more retarded timing, the cht is more responsive, but will eventually balance out the CHT and EGT temps meaning everything runs more stable once jetted properly. It really doesn't seem to have any running issues after the seize. Sure it probably isn't as smooth as before, but it still feels strong.

Will be running tests on MJ going back up a few points again just to re-find the sputter point at wot and work back down.

Take a look at the beginning of the 2007 Stella post, you can see the GSF dyno numbers. Mine was set using the case marks initially and I have a Kytronik. Should have been at about 23 backing off to 16. Was at about 18 backing off to 10 or 11.

Jack, et al.. how do I seal the exhaust stub better to hopefully plug any air leaks at that point? I've got it cranked as tight as it can go without stripping bolts.

I use this on my turbocharged car, exhaust and turbo manifolds. No leaks yet. Its what I plan using on my EGT sensor also.

https://www.amazon.com/Permatex-81878-Maximum-Temperature-Silicone/dp/B0002UEOPA

I might already have that. Gonna try it this week for both.

Are you just coating the exhaust stub prior to putting the exhaust on our are you coating the seam with a thick layer once it's installed?

Pretty much and I'm also using an SIP sleeve that helps due to some aluminum stubs being on the small side. I am using the sleeve to help block off the slot cut in the exhaust connection. Don't think iron cylinders have the same problem. Just make sure there's enough to fill any void and let it fully cure.


Polini blown off Malossi P2 before I added the spring. You can see sealant and the sleeve.

I'll do that next week. Realized today my temps were probably off because i never put the flywheel cover back on after changing the timing.

Was gonna go back up to 125mj to check, but i ran it on stand at wot and saw it was not revving over 6000 so i said f it, Jack is right i need to go down. I worked down from 122 to 118 on stand then went for a quick ride again and it felt good. Also smoked better at wot, where at 122 it didn't smoke at wot. I would say i think it's close except after a few minutes if started bogging at wot. So i returned to garage and pulled the cowl off to realize that my spark plug wire stripped and was bare from hanging too low and rubbing against the flywheel thanks to no cover on it. I think this is why it was bogging at wot.. probably shorting on the flywheel as it made contact with the bare ht coil wire. So i ordered more of that and went back up to 119mj just to be cautious before trying again.

Plug looks better. Will revisit once i replace that wire and recheck temps with all the cooling hoods back on.


118 mj 23 degree idle timing

Wire was rubbing against the flywheel with no cooling sheath on it.

Swiss!
Welcome back brother.
Just doing a quick catch up.
Fly wheel cover CRITICAL to temp. Must have.
Plug - generally - looks pretty good - no red flags.
Plug wire - 14"s of red flag...

Will read back through but glad to see you tinkering.
Quick look - strikes me you are pretty close.
-CM

I had that the other day too. Felt like flooding at WOT but was a busted plug cap, which identified itself by falling off and cutting out, saving minutes on investigation time.

The plug wire that came with the vape kit was extra long probably about 18-20" or so. I left it long without cutting it to length, which was fine when I had the flywheel cover on, but clearly not fine without that cover on. The original owner of my stella also installed this heat insulation fabric on the inside of the cowls, and I noticed before this last run that the flywheel was shredding that heat fabric on the cowl when I saw it ripped and frayed everywhere. Didn't think it would suck the excess wire in and do the same. Probably should have taken the 5 minutes to replace the cover before going back out!

And yeah I've been slowly getting back into thinkin about working on the scooters again for the past few weeks. I just needed time off from it and couldn't even go into my garage for 3 or 4 months out of frustration. Then a couple months of going into the garage and being pissed when I would look at my stella.

But time to clear head and I'm no longer pissed off about it, but have the patience to take the little time to do those tasks I couldn't deal with prior.. like checking timing and making sure it was good. Plus the thought of throwing in the towel just meant I wasted all that money instead of it being worth every penny. I couldn't give up!

Jack, thats basically what it felt like with the wire shorting on flywheel. It was running great but then felt like it was running out of gas only at WOT, and i didn't feel what I would associate with seizing, or hear any pinking so I figured maybe it was just a soft seize and backed off to llimp the mile back home in low gear. Luckily I spotted the stripped wire as soon as I took the plug cap off to check the plug for metal. Saved me some time debugging and worrying again!

The fan cover does so many jobs, not fitting it, is not a corner to cut. Hard lessons.

Remind us of the whole spec and full jetting. Then get back out on the road. Can't be long before NYC is buried in snow.

full spec.. let me try to dig back in my brain and remember this crap:

185/125 cylinder timings
exhaust widened to 68% or something like that
24/24 carb mj passage drilled to something like 2.2mm and 3 paper gaskets in the float bowl.
no air filter on the carb
vape dc variable ignition set to 23 degrees at idle/19 at 6-7000
standard LML gear box, but with 22tooth clutch upgrade
fast flow fuel tap

spark plug I believe was either ngk 8 or 9. I forget right now.
45/140 idle
120/be3/119mj currently

I taped up the ht wire for now until I get the replacement in, and just drove it around on errands this morning for a short while. It feels good but im sure i still need to come down on mj a little. It doesn't stutter at all and four stroke when letting off throttle and wants to take off once it gets over the low rpm hump. probably still a bit rich down low but won't worry about that till mj is settled.

I did decide to take that heat padding off the inside of the engine side cowl today cause I never really looked at it before (always thought it was stock) but i noticed the impression of the flywheel cover on it and realized that its probably blocking airflow massively into the flywheel and hindering cooling of the cylinder. So that crap is torn out and I am curious to see once I start testing temps again how it will do. It sounds great though currently and is fast.




flywheel without cover was rubbing and tearing this.

tear that crap out. lets get some airflow into the cylinder!

Ok time to cheat. Your set up is very similar to Hibbert's bajaj. Jetting won't be so far out.
AC120 BE5 125MJ 48/160
This should help get nearer to fine tuning. As it seized, it's highly likely it was way too weak. Really lean coughing can feel a lot like rich. We've all been caught out by this at some point.

Ordering the be5 atomizer. To understand this.. BE5 is leaner than BE3 in the mid throttle? so to compensate the MJ gets larger? which then solves the problem that a lower mj set properly is still too lean.

btw.. my stella is reed valve. not sure what the bajaj is.. just double checking that cause I know you said reed vs rotary affects jetting.

BE5 is actually richer all round. The reed inlet is bigger but the bajaj has a slightly better cylinder. Should work out similar. Certainly worth a try. Bajaj was going well and likely still is.

BE5 came yesterday, but it has been pouring out for past two days. I've thrown this new jetting into carb as suggested but won't get a chance to test it on road until later this week when it stops raining. Instead I just ran it on stand in neutral under no load. It smokes better at both ends, idle and WOT. Pegging it at WOT for 5-8 seconds under no load and cht stays low, but EGT starts to climb. Wasn't gonna chance holding it for longer to test the upper limit of the EGT. I did not touch the air mix screw after changing to 48/160 but letting off on gas and it settles to idle really well still. Plug looks chocolate but on the dark side. I think it is close like this, but I'll get a better idea once I get on the road and put some miles on this jetting.

air mix screw definitely needs some fiddling cause it feels rich at idle and wants to stall when idling for longer than a minute. Had to turn up the idle a bit to keep it from puttering out after a minute or two.

Richer all around keeps the running bits in separate pieces instead of a molton mess of one. I'm trying to stay slightly rich on purpose, not to worried about trying to get to lean or that perfect color. Makes riding more enjoyable when your not worried about temperatures all the time. I have to resist the urge to try and lean Stella out for that last 0.5 hp at wot. Where I noticed I hardly ever run riding normally around town or driving on county roads with the P200 motor at 60 - 70 MPH. Not trying to get that last 0.5hp at wot. Try to work on better midrange power, stay strong resist the urge.

Open up the exhaust port width while its on the table, its cast iron we both know its hard to mess up. That exhaust port looks worse than my new Pinasco and could use some help. Pay attention to the cylinder studs on both side of the exhaust, you can't open these up as much as the Stella cases or you'll run into a stud hole.

Think you are confusing threads. My stella has the exhaust already widened. But yes I am leaning towards slightly rich once I figure out where it is correct.

My P200 will have the exhaust work done to it, but that is another thread!

Been holding off posting on this thread until I could do some adjusting and riding on my own to try to understand decision making on jetting without constant feedback. Instead of making a change, riding it, pulling plug, taking photo and posting here for advice.. I am really trying to understand how everything relates and why to make different changes by using the plug symptoms, feel and sound to make educated guesses instead of shooting in the dark. Plus it was raining for half a week when the atomizer came, then once it stopped raining it was cold as all hell here for riding (34 feels like 24) on the few days I had some time free to mess with this so I didn't really have much time to do it all at once.. instead made incremental changes over the past week or so and sat on them and thought about them for a few days before making another change.

First thing I did was switch to Jack's suggested 120/BE5/125 MJ stack and the 48/160 idle. Ran fast, but hot and sputtered a bit quarter to half throttle. I thought it was rich, but decided to go up to be safe and make sure it got worse going up before going down. 128 MJ got better was almost clean in 2nd from crawl to wot but temps were still hovering around 300F on mid throttle city streets. So I went to 130MJ and it still felt clean and strong with only the small four stroking/stutter in the first 1/8-1/4 throttle. Temps seemed to come down to around 250 mid throttle. At this point I said f' it im gonna keep going up until the bogging starts happening in 2nd from crawl to wot. Bogging started happening on a 135 mj so I figure this is my upper limit of too rich MJ. I believe my target MJ is a 130, but stuck a 132 in just to be on the safer side (as this 132 still runs clean).

Then I went on a higher speed run in 4th to see what the upper limit of the temps do. I am very clearly seeing the CHT get cooler when I give it gas and rise slightly before coming down when let off gas. I did notice that holding WOT the CHT seemed to still be slowly climbing over 300F and didn't look like it wanted to stop, so I backed off and went back to garage to think about it.

Pulled plug and checked at this point. Plug looks chocolate, but a bit dark still. (first photo attached below). I had checked the plug at each change of MJ and even at the leanest 125 it still looked a bit dark. So I went back to the conversation in my thread from about a year ago where we discussed how to read a spark plug for various symptoms. I was wondering if maybe my B9ES plug was too cold and the reason why the plug looked too dark even at what seems to be the ideal MJ. I had been looking for that demarcation line on the grounding electrode for the edge of dark to light burn mark right at the middle of the bend (just as the image Ginch posted a year ago and is shown below:


My plug didn't look clearly distinguished at the middle of the bend like that. So that was another clue that maybe I needed to go next hottest plug, in order to burn off more fuel on the ground electrode to the correct point on the bend.

So a few days later, I swapped a slightly used B8ES plug in to get the next hotter heat range and run it around for a few miles on the same 132 MJ and see how it changed the plug color. This is where the plug started looking the correct tan/lightly charred marshmallow color, and now I could see the clearly demarcated line on the bend of the ground electrode right at the middle of the bend.


Sat on it for a few days with a couple miles here and there to decide how I felt about the jetting/etc and keep looking at the plug as more miles put on it. Didn't get much miles on cause it was freezing. But while I was sitting inside due to the cold, thinking about the plug, I started wondering if maybe my ignition timing is still not set at the "correct" timing, but just set at a generic suggested timing based on someone elses correct timing for their exact setup, which is close to mine, but not exactly ideal for mine. So I figured I needed to work on finding the correct ignition timing for my specific setup first. I also remembered from that same discussion on my thread a year ago that the center electrode should have a crusty fuel film going from the ceramic center up to about 1mm from the tip of the center electrode. My plug never seems to have that crust line, but just seems smooth dark from top to bottom, with only the slightest white/tan line right around the corner of the tip of center electrode. So I started wondering if maybe my ignition is too retarded and needs to be advanced a little bit at a time to burn off some of that dark fuel on the center electrode tip, hopefully opening up that thin white/tan line only around the hard cornered edge of the top of electrode into a wider 1mm thick clean tip.

Today was the first time I was able to get back out with warmer weather and start messing with it. So I advanced my timing 1 more degree from 23 to 24.. which would make my variable timing 24 to 20 (idle to 7000 rpm). I do not want to go too far advanced as I don't want to start destroying the piston from detonation.. so I only went that one degree more advanced to do a run. Didn't hear any obvious pinging or detonation noises after a quick run, nor did I see any signs of detonation on the plug when I pulled it after that. So I decided to go for another 20-30 mile drive on it with the new B8ES plug, 24 degree timing and 132 MJ combination. It runs great as is, feels strong all the way up to wot (just a little 4 stroking or stuttering in the first 1/8-1/4 throttle). Temps for the CHT would go down with gas, slowly climb up to 300 if held at mid to high throttle with high rpms, but would come down with quick WOT pulses. Temps would go slightly over 300 to maybe 325 if I let off gas at high rpm or if i held wot for over 15 seconds.. so I think the temps are still a bit off from being able to hold wot for days on highway.

Pulled the plug after that long run on 24 degree ignition and the plug looks so much better. Still not seeing the ideal crusty center electrode with 1mm thick clean tip at the end. This makes me wonder if I should go more advanced, or more retarded with the ignition. I'm just not sure if the crusty tip symptom only comes after many miles of riding, or if it should be showing up within 20 miles of hard riding all over the throttle range. Any advice?

My inclination is to think that I could go maybe 1 degree more advanced with timing.. and my mj could go down to 130 or maybe even 128MJ. The trick is how to keep that WOT temp from wanting to keep climbing instead of stopping at the upper limit. I feel like I need to continue down this path of figuring out the correct ignition timing, before progressing any further with the MJ stack.

As mentioned.. first photo below is on the colder plug, 132 MJ stack and 23 degree ignition. All other photos below are on the B8ES hotter plug, 132MJ and 24 degree ignition.


B9ES, 120/BE5/132MJ, 23-19 ignition (idle-7000rpm)

B8ES, 120/BE5/132MJ, 24-20 ignition (idle-7000rpm)



1 point hotter spark plug and now I get the burn line on grounding electrode to the middle of the bend as desired.

Try to be same runs with a 130mj before getting to excited about stronger timing.

Yes I am hesitant to go stronger timing. I just rode around for another 30 or so miles on the 132 and definitely came to the conclusion I need to go down to 130 at least. Plug is also much darker with more miles on it. Just the tip is the nice tan color now.

Outstanding Swiss so was the BE5 an improvement?

Very much so. I can hold the throttle in almost all positions and it will pull and not stutter a lot, with the only exception being down low slight stutter cause I'm still a bit rich. It sounds way more solid and consistent of a bite now compared to before. It's also a little harder to keep the front wheel down.

I've only had the front wheel in the air once, I was working on jetting and was to rich, and revving it to keep the rpm up and running. Pulled away from a stop sign and gave her a bit to much gas.

Swiss - some good work there.
My $.02:
Right where Jack is.
I'd go very easy on timing.
It's hard to know how precise your TDC mark is - and everything is relative to that - but assuming its dead nuts - that's significant advance your running.

What temp gauge are you using?
Under spark plug?

I was thinking about bracketing the timing the other way (retarded) 1 degree from my original timing prior to today, to see what it does to the heat, and plug. So that would be 22-18 instead.

Temp gauge westach dual cht/egt aviation gauge and sensor. Under plug sensor.

Some barrel photos just for reference.

Ok I believe I am very close with jetting and timing. I still need to put a bunch of miles on the plug and do a really hard wot run in 2nd plug chop to confirm the MJ because the plug hasn't built up enough evidence of the most recent changes, but it is looking close on about 15 miles.

I am at 120/BE5/128 MJ. I believe I "might" be able to get down to 125 mj but that might be going too far. I would feel more comfortable drilling my own 127 or 126mj as I think I could safely go down 1 or 2 points, but 3 might be a bit much.

I did have to go down another idle jet size because I was still getting sputter richness in on the low end up to 1/4 throttle no matter how low I went on MJ. Once I changed to the next lowest idle jet of 45/160 everything low end really cleared up and just barely sputters now around 1/4 throttle.. which is partly why I think i could go down 1 or 2 points most on MJ. Going down to this idle jet on a 128 MJ stack is the first time I've ever felt it really cleanly throughout the whole throttle range and could finally hold the throttle in any position at all rpms and not have annoying splutter. It feels great to be able to slowly go up or down throttle while holding rpms just to up or down your speed in gradual increments and not have splutter! It just sings and actually got quieter!

As jack has mentioned, temps actually came down a bit also with this new idle jet. I was hovering around 230-250F at idle on a 48/160 idle and 128MJ. Going down to the 45/160 idle and temps now hover around 200-220F at idle.

Timing I did bracket by going back 1 degree more retarded from the original timing (2 degrees from the more advanced timing test). So I am currently at 22-18 (idle-7000rpm). I can see temps respond appropriately to throttle actions going down with gas and up with less. I am still hesitant to go for a highway run as I can see at high rpm wot the temps go to 300 or 320F and I just don't try to push it when I see those temps anymore. So it may hold there at WOT, or it may still climb.. just too nervous to see what it does.

I think this means my timing still needs work.. and maybe with the fine adjustment of idle and one or two points down on the MJ would cause the temps to stabilize even more!

I will put more miles on it before thinking about any changes.. and take some video of the temp gauge while driving so you guys can see what my temps are doing.


45/160 1.5 full turns out. 120/BE5/128mj 22 degrees timing at idle

45/160 1.5 full turns out. 120/BE5/128mj 22 degrees timing at idle

45/160 1.5 full turns out. 120/BE5/128mj 22 degrees timing at idle

45/160 1.5 full turns out. 120/BE5/128mj 22 degrees timing at idle

This 128MJ looks richer on the plug than the 132MJ. Have you checked the 128MJ is actually smaller? Looks like still 5 numbers over.

Haven't measured them but i will measure my 130,128,125 later. I think it's just not an accurate plug photo cause i really didn't hold it wot for long before taking photo. Need more miles on the plug and a really good wot run. Also I'm two degrees retarded from the 130 plug photo. I'm sure that affects it.

Not sure how useful or accurate these measurements are because I'm sticking a square peg in a round hole then trying to measure the square peg on the diagonal accurately to get the jet size.

SIP 135 MJ measured at 1.28mm
SIP 132 MJ measured at 1.30mm
SIP 130 MJ measured at 1.23mm
SIP 128 MJ measured at 1.19mm
SIP 125 MJ measured at 1.18mm
SIP 122 MJ measured at 1.12mm


I threw the 125mj in down from 128 as more miles plug is dark chocolate and there is a slight stutter/richness around 1/4 or just over it.

Hey swiss are you feeling a stutter or a sputter? Are you feeling any surging when closing throttle?

Wondering if you might be feeling a lean symptom since you're on smaller pilots and only at 1-1/2 turn?

How does a 55-160 pilot behave with the 125MJ? Jack suggest 2-1/2 turns target on fine pitch.

no surging when closing throttle. My idle will fall into place and adjust with the final MJ. I am at 1.5 turns out because the idle is rich. With the one size richer idle, I was at even less turns out. If I were on 55/160 I wouldn't be able to get it to stall out even with closing the air mix screw all the way. Also the idle settles fast when throttle cut completely. If it hung I would be worried.

I'm not too concerned with it as of yet as I haven't fine tuned the air mix screw settings yet casue the MJ is still affecting it and not locked in yet.

Getting closer. Down to 125mj and still dark plug. Gonna keep going down until the plug looks good. Must be getting close cause it runs great.

If its running great resist the urge for awhile to lean it out more, a little rich is better than to lean and a molten mess. Enjoy the ride put a few hundred miles on, watch the temps and see what happens.

Those caste iron cylinders don’t allow a magnitude of sin. I generally ride them rich for the first 500 miles then drop the carb down 5-10 points on the main. That’s how I do it anyways.

You may want to think about honing that cylinder and taking a look at the piston now that it nipped up.