Modern Vespa

I'm not a huge fan of the runleader CHT's, but they at least make one with the M10 sensor.

I did but that 4.5mm one that comes with the sip speedo is absolute garbage. Get the koso 10mm one instead. Easy to install it and much much better than those dang rings!

Aaaand, the crappy little o-ring fell to bits. Where can I find one of those without being off the road for a week?

The hardware definitely gives inconsistent torque, so it will be replaced. At this pace, I will have it run in by November.

Try Grainger or McMaster used both for orings on different projects.

Sip amongst others have them, do a Google ( 😱) half a dozen came up straight away.

Thanks. I measured the o ring at about 71mm ID and maybe 1.5-2mm thick. I hope it's close enough. I haven't found anyone who sells the VMC rings in the US. SIP isn't a great option for fast or cheap for small parts.

I'm not sure the O ring does that much anyway. It's a wide metal to metal contact area and I always use copper coat.

I ordered some o-rings from McMaster. Worth a try. It's not rocket science. It will leak or it won't and it's easy to check.

In the meantime I emailed ScooterMercato who can get them from SIP.

Going to replace the hardware with regular nuts and hex head bolts for the Allen bolts. The Allen bolts buried in a cylinder head is a really bad idea.

Otherwise, I really like this kit. Lots of low end grunt. Even with a rich idle jet, it has great low throttle response and I think the top end will be good too. I found myself hitting an indicated 50 mph pretty quickly without even trying to accelerate and it seems to pull 4th easily.

The 71x2.5mm o-ring looked like a good fit. Head retorqued with nuts and lock washers so I'm back in business.

Forgot about those Allen bolts. They were soft as F -- at least they were back then. Replaced them with harder bolts. The torque spec is very low, but even at that a socket would get stuck in it.

Before I added a sidecar to mine (and developed a leak!) I hit 67(gps) and that was just bolt on and as you mentioned loads of low down grunt

I couldn't even torque those. Too small/deep to fit an Allen socket. I snugged them up with Allen key until it felt tight. I couldn't find hex bolts the right length.

Yeah you need an extended Allen socket. The only way.

On the Egig, same deal, hole is too small and I did them up with a key too until I felt it was tight enough and couldn't do tighten any more with a finger and thumb. But used an extended Allen socket and a torque wrench and it still had some way to go before hitting the spec of 13nm.

I might just weld up a socket. Not the first time.

Absolute garbage those Allen heads are. Or were.

That's the one place this kit falls down. It seems otherwise well designed. Allen heads are a bad idea on anything that isn't furniture, especially in a recessed space. The spacer nuts are a good idea, but they are poor quality. I'm not wild about the o-ring either. It's all a bit gimmicky.

None of these things are deal breakers though and I would still recommend it at this point. Some of the stock stuff can be pretty rough too. One thing I noticed watching an FMP video was that the transfer ports were really ragged. My kit looked much better and I only had to do a little cleaning up with a small file.

I have had very similar experiences with the VW; switching to better hardware, chamfering cam lobes or cleaning up castings on cylinder heads or bearings to make stuff fit.

Went out for a ride on the same route. Same CHT's and stopped to turn around in the same place after adjusting the screws. Rode back going a little faster (50 indicated) and went for a longer ride with lots of hills and it seemed to be better (280-290). It seems to idle best at around 950 rpm. Returns nicely to idle. No blow by around the plug. It's 90 and humid here. I linked a video as I still can't hear rich and lean that well. It still runs way better than it did. I'm a little surprised as it is jetted so rich. The only other thing I can think to try is the spark plug with the crush washer. I ran the other kit with one. Anyhoo…

I'm just going to keep riding it gently with an eye on CHTs and see how it revs out in 2nd once I'm done with this tank of 1%. I can't think of anything else to look into that could be causing the high CHT's.

The O Ring Store is usually way cheaper than Mcmaster. https://www.theoringstore.com/store/

Thank you. I will keep that in mind. Always good to have spares on hand.

Went for a longer ride yesterday. Lots of hills and pushed it harder. It was a cool 67*. Temps topped off at 260-280F, 40-55 indicated. It doesn't seem all that far off from riding last fall.

Feels boggy above 1/2 throttle in 3rd and 4th. I still have a hard time telling the difference between rich and lean bogging. Going up to a 128 MJ will probably tell me. I suspect bogging will be worse. I'm also going to try a 50/100 idle, just to see what it does to CHT's. I suspect the 50/120 is already too rich, but it's worth a try.

I'm wondering at what point it will be safe to:

1. Stop running 1% premix.

2. Full throttle in 2nd MJ test. Yeah, I'm afraid to break it.

Thanks.

To my ear:
- You are rich down low. Even after turn around adjustment. Critical to have the scoot warmed up when judging that (so just swiping idle jet and driving 100 feet on cold motor won't indicate properly). You will eventually be able to knock out some of that 4 stroking at 1/8-1/4 throttle with a bit leaner idle jet I am guessing. How many turns out would you guess you are on after that adjustment mid way?
- Main is not miles off - and you don't sound lean. Best way now is to move to plug and get your read.
- Break in - well - 1000 answers and no hard science. Just our experiences. by 5 heat cycles I am pushing it harder. By 10 I am, all in (iron cylinder).

- Head bolts. My VMC studs had paint on the threads - I removed. The allen heads are useless - largely because they are so SHALLOW! Std allen heads at Ace will be hardened to grade 8 and be deeper. Amazon also good. These have performed great for me after I had to extract a stripped VMC one before I had even broken in the rings... I used harbor freights cheepo allen socket kit - and have found it to be useful on lots of other stuff. FWIW.

I stopped adding the extra ( mine s a px autolube) after the first couple of tankfuls, My thinking is that most if not all the oil lubricates the bottom end and that on my engine had 700 miles or so on it before I bought it.

Thank you!

Yes, CMan22, it's definitely rich low down. I went richer on the idle jet because I was worried about CHT's. It was great with a 52/140, no 4-stroking and great acceleration…and that's not a lean jet.

As for running in. I have been pushing it harder each ride. Another tank full and if all is well, I'll call it good.

Andyx, I agree. It's just the P and C, so I will probably finish this tank of premix and call it good.

Thanks all.

Keep the time at high rpm short and all will be fine.

Get the main jet done first or none of the low rpm jetting will make sense. As before 2nd gear runs at full throttle and max rpm. Full repetitive splutter and not revving out, to begin, then work down.
Can't stress it highly enough, has to be the full wet machine gun splutter at WOT to be sure it's actually rich. Slightly lean jetting coughs and going leaner still stops the coughing.
Be absolutely positive it's rich before leaning down.

Got it. Because I don't have a great ear or feel for lean/rich…I make sure I find that jet that bogs, splutters, 4 strokes so much that it hurts to ride it that way. Just so obviously puke rich that there is no mistaking it.

I'm optimistic. The 26/26 actually responds as expected with jetting changes. The 20/20 ran rich on the idle circuit no matter what. I still don't know why and am still curious.

Anyway, I will do the MJ test next.

Thanks.

Tried the Main jet test today. Would not splutter revving out in 2nd with a 125 MJ. Tried a 128 and couldn't make it splutter with that either. I'm surprised the AC 120 128 main didn't make it splutter. Float bowl is drilled out to 2.3mm.

Full on splutter may be closer to 135.
Think u r probably not to the point where you'd know if it's not fully revving out - because you weren't previously revving it out yet?

Just go up another 10 and see what happens

Yesterday I revved it out at full throttle in second. It hit 9k rpm and was totally clean with a 128MJ. That was the first time since replacing the cylinder. It's been through a few heat cycles, so…

During my ride yesterday, CHT's hit 290 briefly and stayed between 260-280F. Winding roads with lots of hills. It's not really possible to ride faster than 50mph. Rode it the same way I did before the new kit.

Jack221, I have jets in the 130's on the way. Not doing anything with the idle or mixer until the main is sorted.

It's been great to ride, even though it's not fully dialed in. I'm just going to ride it normally, not pushing it too hard until the jetting is sorted and I have a few miles on it.

Tooling around should be fine.
I'm a little surprised regarding no splutter with ac 120 / 128.
Would be tempted to double check 2 things:
- ac120 is truly what I had installed…
- drill had gone all the way through passage

If u flip your 2.3mm bit over and use the tail end, you could double check it's sliding all the way through the hole and bottoming out in mini reservoir.

I've experienced myself thinking that I had drilled it out, but then realized it wasn't all the way.

Drill bit should slide a good 1/4" into hole if I recall correctly.

If you look into the main jet hole, you can see the drill bit in the bottom of it when it's fully drilled out, too.

Thanks!

I will double check both of those things.

Hard to see in the photo, but the AC 120 I was running seems to have an enlarged hole compared to the new one…maybe not. I will see if it makes a difference. If not, I have 130-140 main jets to try.

Bottom one looks to have a tapered or bevel leading into hole. What the other side look like?

Tried the new 120 AC. Didn't make any difference. Neither did going up to a 138 main jet. I'm thinking I didn't go all the way through drilling the float bowl.

Going to take another shot at drilling the float bowl. One issue I had is that the float bowl seems deeper on the 26/26, so it's a difficult angle to drill especially with the short drill bits that are commonly available. So trying to find a workaround.

Also afraid to muff it and wondering if it will ruin the carb if the hole ends up being too large. I'm using a 3/32 drill bit which is 2.3mm.

Thanks.

Did you try inserting bit chuxk end first and look into hole for main jet stack? Should be able to see it if all the way through already.

I did, and I thought I could see the end of the drill bit poking through into the main jet hole, but now I'm not so sure.

Don't know what else it could be…kinked fuel line? Ghosts?

If it's all the way through, it's pretty obvious. No "I think" about it.

Turns out I hadn't drilled the float bowl hole all the way through. It was obvious when I drilled it with the dremel as I felt it break through and I could see the other end of the drill bit when I pushed it through.

I tried again with the 138 main jet. It spluttered at WOT, but cleared with sustained WOT. Enlarging the hole definitely made a difference but I expected a more impressively awful splutter. Still running the BE4 and 120AC.