Modern Vespa

The one thing it won't be is the same. The AC120 and BE4 must stay but main should be smaller and pilot will need to be richer.
26/26 and a vortex will be the fastest option.

I am looking to purchase the Polini vortex and filter kit. I will purchase a 26/26 this week. If not then a 24/24.

Don't buy the Polini vortex. Get an MRP or similar vortex and keep the bellows to frame. The Polini draws hot air from the engine, not ideal…

OK. I will look into to that. Thanks.

Any vortex except the polini and any carb but the 24/24.

Silly question but will there be a noticeable difference in performance between the 20/20 carb and the 26/26?

+1 on the Polini.

Don't get it…

Get the awesome 3D printed one from one of the forum guys… looks top

I have gone for the Pinasco Bellmouth with separate under-seat filter. Looks the bollocks. One of the lads I know has given me a 24/24E carb so I may go with that for now rather than buy the 26/26. Saves me a bit of cash and if it does not work then I have lost nothing for trying.

Awesome.

Yeah I ran the Polini. It wasn't bad… just not very good. Filter got dirty super quick. Sponge came apart.

I wouldn't tell anyone to buy it.

There's a German fella who did a test with the temps around the engine… the Polini would draw air 5 deg hotter than a bellow system…

Not gonna be installing one of those again

I am away at work and can't wait to get home to mess about with it and ride it again. Puts a proper smile on my face when it actually works.

I am back home on Thu/Fri so should be time to fit the new carb and get jetting. I will leave the idle and stack the same, except of course for the main jet. Start high at 140 and should run like crap. Always best to test the main jet whilst riding it and not seeing how high it will rev? Got the new Pinasco Vortex and air filter to fit too. I hear the vortex may cause a higher main jet to be needed? I honestly don't know where to start with the 24/24 carb and vortex. 140 should be high enough as a starting point I hope. You say I may need a richer idle jet, what is richer than the 55/160 I have fitted at the moment? Most places don't sell anything higher than a 55/160. Scooter Centre sell them but it's asking for a minimum order of £140???

It would probably help if you were to recap jetting you want to try so people don't have to try and find it in previous posts. I found it easier and have better results or more feedback when I recap as much of my motor setup as possible. Makes it easier for anyone to reference months or years from now also. Also helped me when I wanted to see what I had tried a year ago.

Current jetting for my 20/20 with no air filter is 55/160 and 120/BE4/138 which is slightly rich and splutters a bit.

By how many jet sizes will having the bellmouth change the main jet? I read another post saying it can increase it by 10 sizes???

Also, will these idle jets be suffice or will they be way too rich?

https://ve-uk.com/product/bgm-pilot-jet-kit-58-160-60-160-62-160-65-160-68-160-for-dellorto-spaco-si-carbs/

Can but might not. Will be bigger than without. Idle jet kit will be ok.

Best thing you can do is get a variety pack or three of main jets. I ended up getting two 10 packs of jets all bigger than my stock jet all same brand. Helps you not have to deal with brand to brand variables. I went from a 160 AC to a 120 AC to stay in those sizes. Always go big on jetting and work your way leaner, that way you know that odd bogging is rich not lean, lean leaves you walking home or getting an Uber. I used those jet packs each time I made a change, exhaust, drilled air filter, no air filter, bellmouth. I was one of those people who went 10 sizes bigger. However you have a lot of different parts than I had, it all makes a difference on how well they work together. I'm guessing my SI20 carburetor was on the small side and anything I did to help it breath at WOT it took advantage of.

I'm one of those people that likes to tinker and experiment. I enjoyed seeing what each did and if it helped or did nothing. You have to embrace that when you start putting kits on a motor or you'll just be frustrated.

I have a good selection of jets now. I think I am covered. I will start very high as always and work my way down to every so slightly rich to be safe.

Out of interest, what jetting setup are you running? Thanks.

It's an LML reed valve motor, with a DR 177 kit and expansion chamber. Jetting won't be the same.

Does anybody know whether or not I can fit a starter ring to the flywheel as to use the electric start? I am unsure whether or not the ring will foul the Pinasco RX 190 cylinder? The bike came without the ring, I assume to lighten the flywheel. I want to buy one, and assume it just slides on as I can't see any fittings for it on the flywheel itself. Thanks.

Parts are here. Will fit them tomorrow and mess with jetting.

With the vortex bell fitted the air box lid won't fit properly and affects the running. Strange

Take a picture of carburetor and vortex mounted with lid off. Picture of top also.

24/24 carb is broken. Jet lodged idle jet hole. Brilliant. So with my 20/20 carb, with a 138 main fitted, the bike is a bit rich as it splutters somewhat until it gets up to speed. Pull the choke out and it keeps revving higher but the low end is really rich. If the choke does not bog the bike down does that mean the main is still too lean? With a 140 main it rides like crap. Very odd. I have fit the vortex to my 20/20. Sort of fits OK. Temps are still 130 to 140 C when cruising. Plug colour is a nice tan brown. Thanks.

When I ran the Polini Venturi, I had a bigger air box lid…

Not sure if it was a must have though…

I've put it away in storage… will see if I can dig it out to see

The bike now takes minimum of 10 kicks to start. I have changed the plug but still takes ages to start. Also the choke has little affect when I apply it at idle. Can't be lean with the 55/160 idle jet and mixture screw 3 turns out.

55/160 isn't actually that rich… and it doesn't matter how many turns out if the idle jet is too small.

If the choke doesn't kill the engine (and it's working properly), your engine is running too lean.

Just did a leak down test on a PX who the owner thought it was running fine…

Video below:
https://youtube.com/shorts/cDOwZG_8LIg

I have ordered some more idle jets. 58/160 is the next one up. There are 5 in the pack. Not arrived yet but I will fit the 58/160 and see how that goes. Apparently dividing the numbers of the idle jet is a load of bollocks for determining the rich/lean ratio. The 55/160 brings the revs down when revved. The engine does not hang and sounds nice with good responses. No popping or banging on the overrun. I will take a look at the choke jet and make sure it's not blocked. Would explain the difficulty in starting also. Thanks.

That's a big leak. Where was it?

Having trouble tracking it down… initially thought it was the intake, couldn't see any bubbles anywhere. something tells me it's the clutch oil seal.

Can hear it around the back.

Could be the crankcase too… unfortunately wasn't put together by myself.

Doesn't hold any pressure…

Owner doesn't want to deal with it yet

Bad news. Riding along and all WAS fine. The loss of power and loads of smelly smoke. Uh oh. Anyway, engine in bits again with a shot clutch side oil seal. The rubber has come away from the seal. Bugger. Anyway I will order all my new bits and start again in a week or so as I truly cannot be fucked at the moment. Going for the BGM faster flow 26/26 and some decent BGM oil seals. I will buy it all from the Scooter Centre in one go. Can't wait to built it all again and pressure test....Not.

Sounds like the seal popped out…

Got to be careful with installing it.

Do you know if your crank is running true? Wonder if it was pulled out because of the crank?

The corteco seals seem to be better made… the BGM one is the correct height (don't need to modify it) but the metal and rubber seem a bit iffy…

To be honest I did think the seal went in too far and was actually touching the bearing. My bad. Going with the BGM as its the correct size.

I had a rubbing seal before too (a really old build…)

Lasted 1000kms before I rebuilt the engine. Got lucky I suppose.

Same here. It appears that no damage has occured. I also forgot to put in the kickstart rubbers so needed to open it up again anyway. Lol.

A seal touching metal is not a problem as that is what they are designed for. You do want a gap between the clutch seal and bearing though (0.5mm). This is to give longevity as when the main bearing wears slightly and develops some side play....you do not want it to pop that seal out. Always fit all metal to non grooved, always lap down slightly before fitting and always fit with a smear of bearing retainer.

The seal was touching the inner bearing race so wore out quickly.

New BGM low profile oil seal fitted. Leak test passed. BGM pro fast flow carb fitted, 24mm. Got a 138 jet in there and it still revs to 9500 rpm. I have the Pinasco vortex fitted with no carb cover so may need to upjet more on the main. 55/160 idle seems a tad lean so will replace this when my new idle jets arrive. All going well until it sheared the flywheel key. Luckily does not appear to have damaged anything. New key on order. Its seems a hell of a lot more perky but didn't ride it for long before it broke.

Good to be running again I'm sure. Flywheel sheared because the taper didn't hold, if it was tight enough, it needs cleaning up.

If you have an AC120/BE4/138 stack it should choke long before 9500rpm. Something not right in the fuel delivery.