Vespa Grande air leak help DR kit

Just installed a 43mm DR kit on my grande with a polini head. Bike fires up and idles just fine but when I give it throttle it only goes about 15mph. I'm fairly new to mopeds but it sounds like a possible air leak?? I lapped the decomp valve on the new head and am running it without a gasket. Using the base gasket that came with the kit. I also sprayed carb cleaner on the head and base seal and the engine didn't seem to bog down.

Was wondering if anyone knows a good place to start with troubleshooting this issue. (edited)

Re: Vespa Grande air leak help DR kit

Did you change your jetting?

Re: Vespa Grande air leak help DR kit

Yeah I’m running a 68 jet right now. I have a proma circuit pipe as wel.

Re: Vespa Grande air leak help DR kit

If your using that aluminum base gasket that could be your problem. I use the felpro gasket material from the auto parts store to cut base gasket. Soak it in 2 stroke oil then assemble.

Re: Vespa Grande air leak help DR kit

Using the paper one that came with the kit. Gonna trouble shoot more later today but I’ll give the fel pro stuff a shot as well.

Re: Vespa Grande air leak help DR kit

Another thing to check is the wires coming off the internal coils. Every Vespa motor I’ve worked on has had brittle or broken wires coming from those coils. You can just solder a new piece of wire in.

Re: Vespa Grande air leak help DR kit

Ok awesome, thanks for all the pointers man. Bike was runnin fine prior to kitting it, so I’m assuming me taking it apart and putting it back together caused a leak somewhere. I’ll play with it more and hopefully be able to fix it.

Re: Vespa Grande air leak help DR kit

new crank seal? theres only one underneath stator plate. No head gasket is fine but both cylinder n head should be sanded for good seal. also, if u use paper for base(something squishy) and u take it off u can see its imprint and what sections (thin) might be marginal for sealing. spraying w fluid all over all sides will find your leak.

Re: Vespa Grande air leak help DR kit

Richard Eberline /

Piston arrow, maybe 180 degrees off. Let me know what the instruction say.

Re: Vespa Grande air leak help DR kit

Arrow is pointed toward exhaust, the windows on the piston are facing up. Carb got clogged up not long after testing so I’m evaporusting the tank for a few days before testing again. Added a malossi head gasket on there as well for good measure.

Re: Vespa Grande air leak help DR kit

> Hunter O. Wrote:

> -------------------------------------------------------

> Arrow is pointed toward exhaust, the windows on the piston are facing

> up. Carb got clogged up not long after testing so I’m evaporusting the

> tank for a few days before testing again. Added a malossi head gasket on

> there as well for good measure.

Install an inline paper fuel filter , good to at least 60 micron .

Re: Vespa Grande air leak help DR kit

Got one of those as well for when I’m done cleaning the tank.

Re: Vespa Grande air leak help DR kit

> Hunter O. Wrote:

> -------------------------------------------------------

> Got one of those as well for when I’m done cleaning the tank.

Good move . It'll save a bunch of hassle . ;)

Re: Vespa Grande air leak help DR kit

Had that on the first time I tested with the new kit, evaporusted it before for 3 days then flushed it. But after a day with new gas a weird jelly/oily substance formed and clogged the petcock and paper fuel filter. Hopefully this next evaporust will fix that. Gonna flush it with rubbing alcohol this time though.

Re: Vespa Grande air leak help DR kit

you've been slimmed

Re: Vespa Grande air leak help DR kit

If that jelly happens again , post a pic of it .

Maybe someone can recognize it .

Re: Vespa Grande air leak help DR kit

Mopeds mo problems

Re: Vespa Grande air leak help DR kit

I still have the post evaporust gas with the jelly I’ll take a photo later and post it.

Re: Vespa Grande air leak help DR kit

Pic of jelly oily gunk that appeared after I used evaporust

12B1437D-CBD0-4EBB-9799-56A8F73E11D6.jpeg

Re: Vespa Grande air leak help DR kit

another

6EC07C2F-936C-4086-839B-B844893F1BD5.jpeg

Re: Vespa Grande air leak help DR kit

Hmm , maybe a concentration of the yellowish crap that coats the insides of the carb bowl when using the junk gasoline they sell us these days ?

Re: Vespa Grande air leak help DR kit

looks like water.

Re: Vespa Grande air leak help DR kit

Richard Eberline /

Water sinks in a gas/oil mix. The yeller tint is Rust. Ethanol gas, keep using that junk. ethanol free gas is my choice

Re: Vespa Grande air leak help DR kit

Good to know, gonna flush it thoroughly next time with alcohol then cycle some gas through it before I put in the pre mix. Thanks for all the input.

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