Modern Vespa

I shot some video of the porting process for those who might not be familiar with it, along with a little bit of zoom-zoom in its current state this evening. Lots of buzzing noises in both.

buzz:
getting to buzz:

Very nice - I especially like your flesh tone riding pants. Everybody would think you're wearing shorts!

I was just showing off my scar

Lol… good old Tesla, can't say I'm not impressed… unlike the wife… lol

Anyone still going at the scooter after the 3rd explosion has an inner monk.

You've come to peace with trials and tribulations… best state to be in.

Says me who was swearing at the dropped small frame engine just today…

108, my Third Explosion happened so many years ago I can't even remember it at this point.

A couple things really keep me going. First is that I enjoy just doing the work.

Second is that I know what I'm doing is possible, it's just really hard to get right. So long as I'm able to dig in on why things failed, figure out the next iteration, and then execute on it effectively, I'll keep at it, building stupid- and stupider-fast motors just because I can.

I guess I could take up golf or something, but I find it really boring and don't particularly like most of the people I know who are really into golf, whereas I find that people who are really into vintage Vespas have a very similar DGAF/You-do-you philosophy as I do.

Tonight, I got the new bearing in, closed up the GL's cases, and the weld (along with the rest of it) passed a pressure test, so tomorrow I'll finish putting it all back together.

Up and running again…

The best

Not quite up and running, but nothing interesting between now and that point. Just gotta put the tire and exhaust back on, then hook up the fuel pump pulse line and plug in the electricals.

I'm ditching the wide 11" wheels and going back to regular 3.5x10 tires. They're really more trouble than they're worth, I've decided. Maybe I'll miss them enough at high speeds to swap back, but that remains to be seen.

Which 11" tire did you end up
using? Why don't you like them?

I'm running Heidenau K61 120/70's.

They're really too wide, so that was my first mistake, but they are just a PITA to deal with when dropping the motor, and I've fought with rubbing on both the front and rear the whole time I've had them. They also leave the bike a little less nimble than stock wheels, which I've become much more aware of now that I'm also riding the VBB a fair amount.

I hesitate to ditch them, because they are really good tires. Sticky, great at high speed, and track really well. But I also have 3.5x10 K61's on Pinasco Tubeless rims which will give me back some of the nimbleness, not cost me anything in terms of stickiness, but without the rubbing issues and, honestly, most of the time I'm not going over 50, so the highway performance doesn't really matter.

Maybe I'll change my mind again after I do the swap, but even if I do, I won't change back until the next time I have to drop the motor.

Ok, I went with same tire in a 110, supposed to be about same as a 3.50x10.

I think I'd have been okay on the rubbing with 110's, but they'd still be a PITA to deal with when dropping the motor.

Why such a PITA? Too tall to exit frame easily?

Yup. Had to drop the motor out of the rear shock to get them on and off the hub, which along with the tuned pipe, meant that I had to raise and lower the motor on and off the rear shock a couple of times to drop the engine.

I put it all back together with the 10" pinasco's tonight and I think they're going to be fine. The rear brake tends to lock up on hard braking, but I just need to change my riding style a little bit.

The motor doesn't feel quite right, like sluggish. I may have overtightened the clutch cable a little, sol I'm hoping it's just slipping a little. If that's not the case, it'll be time to re-tune the carb or figure out what I missed in the rebuild, because it just doesn't have the kick it should.

Always something with these things.

Spoke too soon…

Usually smooth runnings… wonder what's missed?

Take it slow… extra day makes all the difference

That's the question. It feels like the port timing is too low or the jetting too rich. I didn't make any jetting changes as it was deteriorating, but I'll be checking what I can without tearing anything apart to start.

First, I'll verify squish since that's a known measure (.8mm) and make sure it's still accurate. If so, then timings can also be assumed good.

Next, verify timing, although I aligned to a mark I made before the teardown.

Next, I'll throw the AFR on it and see what it has to say about the state of the carb.

Funny thing is that I had something similar with the VBB, where it was pig-rich, so I cleaned up the tuning, at which point it became too lean and I wound up right back where I started jetting-wise.

Sooo irritating.

Yeah, it's most irritating when not much has changed, and it runs terrible.

Or maybe a lot has changed without knowing, which can be equally as bad.

Yeah, that's much worse. Assuming that squish & timing are good, I'll try riding it a little and see if it's just got carb cleaner still in the system or something.

So long as I don't need any parts, I've got a whole long weekend coming up to fight with it.

Well...tried to take the GL out last night and it's just running like crap. Won't rev out past about 4800 RPM's, so won't get up on the pipe. Just stumbles.

It starts and idles about right and settles back to idles like it should, plus it passed the pressure test when I re-assembled.

I didn't have the energy to look last night, but this morning I'm going to make sure I don't have a bad electrical connection, followed by cleaning carb jets.

One thing I noticed, and this may just be that I've been riding the VBB the past few weeks, is that it seems very loud from the motor side. That might just be the reeds combined with the trumpet effect of the side draft, but it was very noticeable to me.

Finally, since I put the sportback seat on the VBB and the OG seat back on the GL, it feels like I'm sitting really high on it. I know it's only like an inch, but it makes a huge perceptual difference.

Yeah, I don't think I could go back to original seat on my Stella, I would like to find something lower than sport Nisa seat I have. I think gas tank cap is an issue. I don't want to sit on fiberglass or plastic either.

I love my TSR sport seat. It's also pointy at the front, so it lines up with the shape of the frame better than most of them. Unfortunately, it's also out of stock (and has been for a while) at all the usual suspects. I think Scooter-Center might have it, but that's it.

Take out a measuring tape, you'll be surprised.

My GL with a standard seat sits almost 3.5" higher than my Super with a sport seat.

I was comparing GL to GL, but totally agree that you'd get 3-4" of difference between 10" and 8" bikes.

That's comparing 10" to 8", so 1" of seat would be ~3" of total height. My VBB was definitely lower than my GL or Sprint even when I had the OG GL seat on it. And now that I have the OG GL seat vs. sport VBB seat, it's a huge difference.

The GL is running the keihin, right?

Yup. I went through it and at this point, I'm at a bit of a loss.

The reeds are coming to the end of their days, so I need to replace the petals sooner than later. I checked them again and one of them was swapped, so I put it back in backwards when I inspected them. That fixed the spitback issue, so one item fixed.

I went through and gave the wires to the CDI a good shove into their connectors and it seems to be firing correctly.

Now, it won't rev past 5020 RPM's under load. No load, it'll rev past that, but with any load on the motor, it's like it can't quite get up on the pipe. I put the AFR on it and the mixture looks good, so I'm ruling out the carb, electrical, and now reeds.

I forgot to check squish, so I'll do that when I go back out, but assuming squish, ignition timing checks, and port timings are correct, I'm just at a bit of a loss why it won't get on the pipe, given that it had no issues doing so previously.

That's really strange.

Nothings changed since you patched up the hole

So I'd assume it was running rich (maybe) to compensate for any leaks, then the big hole happened…

But if the mixture is correct, has to be electrical. Strobed it again?

Doubt it's squish… unless you missed a gasket or 2…

Sooo...I checked the squish and it was 0.4mm. So missing a .5mm gasket. Naturally, it's a base gasket. Looking at pictures from my rage welding adventure back in March, I definitely had a base gasket in addition to the spacer.

Before I went and looked at pictures, I pulled the head and checked the PBT and it was 3.05mm. When I looked at my port timing spreadsheet, it was 3.5, so more confirmation that I should have a base gasket. Not having it knocked my transfer timings down from 125 to 123, which I wouldn't think would be enough to keep it from getting on the pipe, but apparently it is.

In the meantime, I put another 0.5mm head spacer on to see how it would do, and it's actually worse than before. Will barely rev past 4,000 with a load now.

So I guess it's time to pull the cylinder off and reinstall that base gasket, wherever it went.

Maybe that'll happen today. Maybe it won't.

No way…

Forgotten gasket…

I really still doubt it is about the two degree difference in transfers. That little off should not make such drastic difference.

Have you strobed your ignition timing again already? Also you could try to set your spark plug gap smaller and see if it makes a difference.

Can't imagine that port timing or too tight squish would stop it revving. Will be interesting to see what it is. Piston upside down anyone?

I wish it were something that simple at this point, but I happened to shoot a picture of the piston head before I buttoned it back up and can see that it's correct.

I agree that the port timing shouldn't make that much of a difference. This motor should have enough power that even poor performing is still faster than most scoots out there.

I'm going to check ignition timing and install a new spark plug next. If it's something as simple as a new spark plug, I'll take it.

If that doesn't resolve the issue, I think I'll try a RoadXL from the parts hoard and see if that makes a difference.

Would a fouled, but not totally stuck, piston ring cause something like this? I'm just throwing random stuff out there now.

You know you want to put it back to a known good setup and go from there.

I'm trying!

This wasn't a tuning project, this was a repair project after the crank and JBWeld both exploded (along with the clutch plates a few days before that).

Other than than the missing base gasket, this is supposed to be the Known Good setup, hence my frustration.

Yeah the GL was running great before… looked awesome in the videos

Reaching for straws guess:
Exhaust blockage, like something fell into the pipe unnoticed(?).

Not saying this is the issue but I have a SIP flywheel that stops working properly above 5,000 RPM so could be something unrelated to the build.

Digging in on electrical, I swapped the plug to start. No difference. I'm apparently out of spare new plugs, so I had to see which of the random used plugs I had would work. This was not all bad, because it caused me to throw out the various fouled plugs that I've never thrown away because I'm a hoarder.

With a Known Good plug, I finally got to timing. I had to re-mark the cases and flywheel, but once I did, I put the gun on it and...it was firing at TDC at 5,000 RPM's.

(That's one per degree of timing fail, btw)

So whoever had "timing set to TDC" in the betting pool can claim their prize.

Naturally, while I was adjusting the stator, the first rain in two weeks decided to roll in, so now I'm waiting out the thunderstorm to see if that's fixed it, but my gut is that it has.


That's not right!

And now there are two on this forum feeling for the exact same reason

Yup. I've been savoring the irony!