AV7 parma issues... piston clearance


i was replacing the motor mounts on all the mobys with Peter's mounts. i have to say that i totally doubted the drastic improvement but, damn does it make a difference...

anyway, while i had the motor off i snapped some pics of the piston clearance issue with the parma 70cc.

right now i'm running the thickest base gasket material i could get in order to keep the pison from hitting the head, which is a stock 50cc head.

you can see in the pics that the piston is far from clearing the exhaust port and if i were to notch the piston i would have to notch it right down to the ring. it also doesn't clear the transfers.

what do you moby experts think? is it possible that the crank is too long on the stock case? i don't really know and i don't want to mess with the piston if it's a crank issue because that'll make the kit junk if i ever have to replace the bottom end... if i had another case with a crank installed right now, i'd try it out but, i'd have to pull apart another bike to get one.

oh yeah there's a pic of the treats CDI there too...


<a href="http://s47.photobucket.com/albums/f187/lsaffron76/?action=view&current=IMG_1169.jpg"; target="_blank"><img src="http://i47.photobucket.com/albums/f187/lsaffron76/th_IMG_1169.jpg"; border="0" alt="Photobucket" ></a>

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AV7 parma issues... piston clearance

Get the dremel out and chop that piston to bits

Re: AV7 parma issues... piston clearance

dont go all the way to the ring, but i went pretty damn close and she runs pretty damn good.

<a href="http://s112.photobucket.com/albums/n180/monkeyonagriddle/?action=view&current=parmakitwork1006.jpg"; target="_blank"><img src="http://i112.photobucket.com/albums/n180/monkeyonagriddle/parmakitwork1006.jpg"; border="0" alt="Photobucket"></a>

<a href="http://s112.photobucket.com/albums/n180/monkeyonagriddle/?action=view&current=parmakitwork1010.jpg"; target="_blank"><img src="http://i112.photobucket.com/albums/n180/monkeyonagriddle/parmakitwork1010.jpg"; border="0" alt="Photobucket"></a>

another reason you have to use thick base gasket material is because at TDC the bottom of the piston likes to uncover the bottom of the exhaust port

Re: AV7 parma issues... piston clearance

that piston looks great, i guess that's the way to go... what seems strange is that not everyone has this prob. some people say it clears fine.


Re: AV7 parma issues... piston clearance

The head clears the piston on mine, but the exhaust port doens't open all of the way! I will be shaving it soon. also the bike runs 53+

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