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I finally got my dads old vespa 90 running... been sitting since 75/76... It runs and holds a little fast idle with choke out. When pushed in it dies slowly over about 5 seconds.

Can you help with getting carb adjusted right and holding idle with choke in???


By the way-- what a blast! All 3 gears very smooth... Tires.. well, they're 40yrs old but held air last 3 weeks... time to order some since I know it's a keeper!!

Thanks for help getting idle set ......
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Try simple thing 1st.. have you tried turning the idle screw up (clockwise) ? See if you can keep it going after you push the choke in.
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What usually happens to a scoot that's been sitting is that the crank shaft seals dry out and crack. It sucks in some air through those cracks and the fuel/air mix gets too lean for the engine to run. When you pull out the choke, a little extra fuel is added to the mixture and it will run. The small frames (which includes your 90cc) sometimes also leak around the connection from the carb to the engine. That's another thing to check out.

It's not a good idea to ride it around with the choke on. Get that sorted before you go too far. Good luck with it.
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Ive tried turning the idle screw in all the way then backing out to half/full then 1.25/1.5 then wide... wont hold idle when choke pushed in.

I greased up a new felt gasket and have the carb seated well back. Think it's seated back pretty well.

Keep the suggestions coming and I'll keep trying to figure out. I've only run it about a mile and runs great minus holding idle w/ choke in. I slowly push in and there's a point it just drops off and will stall out.

thanks for what you send.. want to try all "simple" options first. I'm not the greatest wrench but have gotten it this far...
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Tried idle screw ... no other possibility other than crank seal??

Anything else I'd like to try first... you got a suggestion shout...otherwise it's tear into things much more...

thanks
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sswells wrote:
Tried idle screw ... no other possibility other than crank seal??

Anything else I'd like to try first... you got a suggestion shout...otherwise it's tear into things much more...

thanks
Hello swells. Sounds like it could be a gummed up idle jet. Take the carb off again, remove all the jets, get some carb cleaner and clean the snot out of everything. Spray it in every opening. Blow air thru, spray more carb cleaner, blow more air, etc. Stay at it, you'll get it to idle.
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Carb work it is... thanks - will let u know.
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Right on. Also, some people swear by a product called Seafoam. While I personally think most gas additives are snake oil, it appeared (emphasis on "appeared") to have helped dislodge some gunk from our carb after it was sitting for an extended time. Couldn't hurt to give it a try.
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A bad oil seal will either cause the engine to rev (when it sucks air) or smoke and stumble (when it sucks crankcase oil)...

As SoCal wrote, it sounds like your idle jet is clogged. They are small enough that the hole can corrode shut with long periods of sitting, try putting a wire thru it and work it around to clean it up. Or just buy new jets, they are cheap!
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A bad oil seal will either cause the engine to rev (when it sucks air) or smoke and stumble (when it sucks crankcase oil)...

As SoCal wrote, it sounds like your idle jet is clogged. They are small enough that the hole can corrode shut with long periods of sitting, try putting a wire thru it and work it around to clean it up. Or just buy new jets, they are cheap!
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I'll throw my hat in the ring with a +1 on cruddy carb jets. A friend's P was doing the exact same thing. It only idled with the choke out. We cleaned up tHe carb and it's been running perfectly ever since.

Hopefully that's all you need.
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Also, make sure there is a bit of slack in the throttle cable. Seen bikes that were "sure to have bad seals..." and all it was is the cable holding the slide open.
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make sure the case has the right amount of 30 weight non detergent oil in it
did the old stuff smell like gas...??

if the idle adjusting screw is not changing the rpms when turned you can fix this by bending the idle screws bracket slightly so the screw is more effective.

have fun
be safe

- alway test your brakes before going "fast"
- for the next 500 miles = ride with your left had hovering over the clutch in case you have to pull it in fast due to "lockup" or seize
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and

you can remove your idle jet with the carb body still on the manifold

it is the small brass slotted bit (jet)...

the screw driver is pointing to it in this pic:
External inline image provided by member with no explanatory text

compressed air and carb cleaner are your friends

http://website.lineone.net/~smallframes/carb.htm
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All is well. It was the idle jet after all.. I rebuilt the carb but didn't apparently get that jet clean enough. Idle is fine w/ choke.

spider-- I changed the oil prior to even kicking once. It didnt smell of fuel then but will change again after a few miles just to check.. Easy and cheap...

Thanks all for the help.. a few miles on Easter, what a present..


Thank you Easter Bunny... and forum...
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