av7 case won’t seal

Original av7 case for motobecane 40t will not fucking seal!! I’ve opened and resealed several times and cannot rid myself of an air leak. Same spot every time, just below intake (but def not intake itself).

I’ve tried sealing with no gasket, a dry gasket, gasket in 2 stroke oil maybe three different times, and finally a dry gasket with yamabond 4 spread thinly on each case half.

Is it warped? Time for new case? Just live with it? What would you do?? Next try is yamabond without a gasket but wanted to put the Q to all you fine folks before I tear it all apart for the nth time.

Performance is OK, torque is great, and I’m jetted appropriately (72ish - see bike specs below) but when I hit an incline it suffers. I live at the top of the hill so this is an issue.

Setup, FWIW:

Stock variator

SHA 15.15 w filter intact

Derestricted stock exhaust

Ported stock fast cylinder (swapped for 70cc Airsal kit, leaky case affected it exactly the same)

Le Partie CDI

11/54 gearing

Brand new seals and bearings

Re: av7 case won’t seal

Totally normal JBOT /

Can you see a divot in the cases?

Try putting the cases on glass and sand flat.

Then use motoseal by itself and I bet you’ll be ok

Re: av7 case won’t seal

Andy Nielsen /

Not a bad idea. One side has a lip, though, so I can't lap it. Definitely a few little nicks here and there. But yes, next move I think is going motoseal sans gasket!

Re: av7 case won’t seal

Totally normal JBOT /

You can lap it.

You can do it by getting a piece of hardwood and flattening it, then cut a hole that matches the area you want to flatten so the lip rises inside and isn’t touched.

Then add sandpaper and spin it.

I do this for cyl bases after cutting them on the lathe. The cyl skirt is in the way but with a jig it’s easy to flatten

Re: av7 case won’t seal

Totally normal JBOT /

Wooden jig


Re: av7 case won’t seal

Andy Nielsen /

Smart— will give it a go!

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