Modern Vespa

Probably need to modify the air filter setup for any kit.

The normal air filter is way too restrictive.

It's delivered as a bolt-on, with easily dremeled port "gates" should one want to open it up.

I found just remove filter and use bellow to frame, that will keep you from sucking up big chunks.

After you get comfortable with that, install one of these and up main jet about 10 sizes.

https://www.shapeways.com/product/CNUFQJZ6D/bellmouth-si24e?optionId=63521802&li=shops

Suspect it's more a matter of difficulty to jet over time(?).
The BGM literature says to use a non-drilled filter

*There are 2 versions of the BGM. One for E-start and one not compatible.
The one I linked to is not the E-start version!

Hmmm, not too sure about that, adding a kit and not need to de-restrict air flow?

Doesn't make sense in my eyes

Even with stock setups people are drilling out the air filter.

Ooooo… this is cool…

What's with the shape?

And there's more 3D printed parts!

I just ended up buying a 3D model from a nice fella in Germany

He turned it to face the inlet, straight up it was getting really close to the box top on a 24mm carburetor, if I remember what I read correctly.

Looks great

If you have no one to weld and machine it, then this is what I would do. The JB weld is a good option to get you running.
Clean up the area well. Make a flat plate like a packer with a conrod hole to keep it flat while it dries. Smear some grease on it so it doesn't stick to the plate. make a gasket from some gasket paper. Blue hylomar. Should work out fine.

Spend the money on a 26mm carb. Match the ports and tune the inlet when you either have the confidence to do it or can find someone to help locally.

I will try this today. I am just waiting for the bits to arrive. I am going to fill that gap on the cases with JB Weld so it at at least covers the exposed transfer ports. GO from there.

And I'd suggest you use Threebond 1215 or Permatex Motoseal1…

I have some Loctite 5660 or something. I have 1207F but apparently that is to seal cooling systems. So no good here.

JB Weld done. All put back together with a homemade paper gasket. It holds 240 mm/hg for a minute with slight loss but I think that is coming from my cheap leakdown kit. I will leave it all settle overnight and put the bike back together tomorrow. I hope this fix lasts. Suish is at 1.5mm but nothing I can do about that unless I take something off the head.

Thanks for pointing out the area that I needed to concentrate on. Much appreciated.

Didn't make sense here either.

Played with filters a bit. An un-drilled filter is a restriction. Fouled filter is a restriction. Drilled clean filter vs bellows-only no difference.

My problems with filters were having jetting change depending on the condition of the filter, and jetting with an older filter before replacing it

Great!

I rode with 1.7mm on the VMC 177 before correcting it. In my anecdotal experience some loss of power but not dangerous.

A CHT may help out here. You'll know if you get an air leak later, as the CHT will continue to climb past your known(no leak) temperatures on given rides.
https://www.amazon.com/gp/product/B092CDSQ33/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I have one of these fitted. A trail tech one. What nax temp should I stray to worry about? Thanks.

I here your frustration. Despite the simplicity of these engines, they have their own tedious learning curve, especially when deviating from the stock setup. As a beginner, I have often been humbled with struggling with the simple things. The costs also add up with a multitude of small orders. There always seems to be a handful of small parts missing or broken that stops you in your tracks and requires yet another order that costs more than expected.

I have read many engine build and tuning threads and even those who are quite good at it have gone through many of the same issues and often still do.

I have lost my shit more often than I expected doing fairly straightforward work on my bike. I expected it to go better, having experience building VW type 4's. When I feel like kicking it over, I walk away. If I still felt like that when coming back to it, I would have no problem admitting that it's just not for me. But it seems to be part of the process when working on quirky vintage stuff. My VW bus engine took 3 attempts to get right and many times I felt like setting the whole thing on fire. But now I can drive it anywhere without worry because I know it inside and out. Eventually, I will get to that place with Vespas and I think you will too. Hang in there.

I try to keep below 190C but its all relative. I have the temp sensor screwed into the middle of the head (BGM187), when I was using the temp sensor on the plug it was reading 50-70C lower.

You just find what temp yours runs well at and use it as a diagnostic/early warning if it strays beyond your personal operating temp.

So the engine lives. Sounds much better although now running massively rich. Running with just the carb cover and no filter. I will have to mess around with the main jet to get it just right. I think I will leave the 120/BE4 setup along with the 155/60 idle jet. Any thoughts before I set out riding it tomorrow?

Not had time to order a new carb yet. I know the 20/20 is not ideal but it will run well enough for what I want at the moment.

Thanks.

That is some difference. Mine is the under the plug type. Trail Tech.

I fully agree. This is my first vespa. I really like riding it and messing about with it. I just did not expect so much messing around after only 5 weeks of ownership. I will stick at it until it's running how it should.

Great!

After correcting jetting, break-in and another leak test, I'd establish some known no-leak ride temperatures, under ride conditions you know(facing wind, hills, etc).

If it climbed quickly to 310F+ under the plug on test rides, I'd turn back.

Sadly, 'tis the tale many of us have dealt with with more fully kitted bikes like yours. But good on you, sticking it out, you'll be super knowledgeable about your bike and really "own" it when it's all done!

Thanks. Hopefully it all pays off.

Working on these bikes especially when tuning them will be frustrating and painful for the first few years, but luckily they aren't that complicated bikes, so once you run into all the problems, you learn how to fix all the problems and things get easier. Takes a few years to get to the point where you can recognize and solve most basic problems with minimal stress. Either people give up before they get through the teething process or they force themselves to get past it.

Keep at it. Things get better!

[quote="swiss1939"]
Working on these bikes especially when tuning them will be frustrating and painful for the first few years, but luckily they aren't that complicated bikes, so once you run into all the problems, you learn how to fix all the problems and things get easier. Takes a few years to get to the point where you can recognize and solve most basic problems with minimal stress. Either people give up before they get through the teething process or they force themselves to get past it.

Keep at it. Things get better!
[/quote

It must have been leaking since I rebuilt it. 500 miles ago. It's a wonder it didn't seize or do damage to the piston and cylinder. Lucky but I was running it and not thrashing it.

I made a leak tester with stuff I had kicking around my shop and swiped my kids ball pump. Granted, I have more crap than the average person.

I found a leak on a 200 I'm putting in my Stella. I was able to fix it thanks to my crappy little tester. Making it and getting it to work took a stupid amount of time, but now I know how to do it and it will be useful in the future.

I placed a sheet of rubber under my carb box and bolted it all back on. Then just a cheap hand pump blood pressure tester and bike inner tube. Works OK. Needs must.

I have been our for a ride. 138 main jet is still a bit rich as it splutters a bit when wound on from around 3000rpm. It feels rich low down. Revs don't feel snappy. Doesnt pop on the run down. Nice and quiet. I will put a few more makes on it and then take it to the dyno to get it dialled in properly. Riding at a steady 50 gives a cht of around 125 to 130 degrees C. Not giving it much throttle at those speeds. Maybe 1/3 max to cruise. Choke stalls bike at idle and slows bike down when riding and giving it some.

Good cruising temperature nothing to worry about. Why not go down a main jet size or two until it cleans up? Give it some time to break in.

How much does a dyno cost in your area? Unless a dyno is cheap, I'd think hard about a 24 or 26 mm carburetor first. A 24mm is what normally comes stock on a P200 and you should be putting out more power than a stock P200. Get that roughed in like 20mm you have now then get a dyno, to dial it in. Jets can be moved from carburetor to carburetor so your not out money for jets.

I am off to work for a couple of weeks but will hopefully have a 24mm/26mm carb when I get back. Will the jets be much different going from a 20 to a 24 carb? Will the main jet go up or down? I think the main jet is slightly larger than normal in the 20/20 carb as I am running no air filter at all. Just the top cover and snorkel.

Now the bike is running well, apart from idle transition to higher revs, is it worth chaning the 55-160 idle to a leaner one and if so, which one. Very slow to rev up from idle but then really revs fast and high.

Thanks.

Do a sound recording. 55/160 is unlikely to be too rich.

I am at work for two weeks so will add one when I get back.

When people advise to drop a jet size, is that a single number or a few numbers? So if I drop from a 138 to 135, is that one size or 3?

3, you need to look up what is available, sometimes you can only get even or odd increments depending on range. What people are usually referring to is next size you can get to see if that's enough change without going so small or big you break something. Baby steps for jetting.

OK thanks. Just because some jet numbers I can't get hold of so impossible to go down just 1 size.

I'd say one since there are no in between jets. 138 -> 135 -> 132…

When I fit my new 24/24 or 26/26 carb, will I have to change the Air Corrector, currently 120 or the idle jet, currently 55/160? Also, can I expect the main jet to be bigger or smaller than my current 138 (rich) that is fitted to my 20/20. At the moment it seems very rich when revving from idle as the response is somewhat delayed. I will post a video if this site allows of the idle pick up. Thanks.