installed the treats...reporting in :()

So first i put on the dellorto sha 16 mm carb, it had an 89 jet in it and the thing didn't run that great. next I installed the proma gp pipe, and a new plug. thing was fouled to hell.

69 jet and thing really came to life, still rich at wot wont top out like i want her to but pulls good in low and mid

65 jet and new plug, really fast, kinda scared it might be too lean. thing pulls like hell and screams at full throttle what you guys think is 65 jet to small?

only ridden it ip the street and back twice, plug has little to no residue from oil on it, i backed out the mixture screw alot and it idles nice, still worried i might be lean, plug looks pretty white just a little bit of brown but havent ridden it much at all.

Also what does mixture screw do ?

Does it change settings at all rpm?

Re: installed the treats...reporting in :()

what is your setup?

Re: installed the treats...reporting in :()

Mixture screws on SHA carbs (assuming it's the single mixture screw one) are simply idle mix screws. I always found the best way to tune them was to screw it in until the RPM goes high enough that the wheel engages, then screw out from there until the wheel stops and the engine runs well (You should be able to tell by ear.)

SHA's are very easy to tune! :)

As for the jet size, I have no idea. My 14mm SHA had a 57 jet in it stock, and I think I was running a bit rich at times (though it was probably just the engine being in bad shape as well causing it to stall when idling...the clutch was sticking). You would need a bit larger jet for the 2mm more size, and then the exhaust factored in. Also if you're running a non stock airbox (high flow) that requires a larger jet as well. So basing off my stock one with no mods, I would say that 65 sounds about right.

It's always safest to run a bit rich! Throw a 66 or 67 in and see how that works out for you. I'm not an expert, but it seems the right thing to do.

Re: installed the treats...reporting in :()

oh yhea no air filter just that thing that came on the sha carb and ive got a proma gp pipe.

Re: installed the treats...reporting in :()

any other ideas, do they make 67 size jet? i found 66 and 68.

Re: installed the treats...reporting in :()

first off plug chop break>

that will give you the best idea of how its running. go from there. good luck.

Re: installed the treats...reporting in :()

Dellorto direct has the odd jets most shops don't. on my vespa SHA to ajust the Idle screw i put in in all the way, not crazy tight, just where it hits home and the screwdriver blade is flat, and than back it out 1 1/4 to 1 1/2 full turns and go from there, but its always perfect at 1 1/2. That screw is for idle only it doesn't change anything about how it runs once you open the throttle. People run 66 jets in 13mm Vespa SHAs ( thats what they come with) on 50cc so if your well above sea level or a place where it's pretty warm..... Take a look at the spread sheet. I love that thing.

Re: installed the treats...reporting in :()

yeah all that the idle screw does is stop the slide from closing all the way. it has no "mixture" changing properties.

Re: installed the treats...reporting in :()

shit talkin' hippy /

yeah a jump from a 69 to a 65 is pretty big, try something in between those, you'll probably find it proper.

I tune mine by finding a jet that just fourstrokes a bit on flats at top top speed after a few minutes of running, then I put some holes in the airbox 'till it stops fourstroking but keep a little fourstroke when I'm really flying down hills.

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