Transfer port openings on my DrEvo

[CoolvetteTopic starterBerichten: 107]

I have a little concern about the transfer ports on my DrEvo, see the pictures.

As you can see neither the transfer ports nor the exhaust port is fully opened, it may differ more than half a millimeter.

It doesn´t feel right to not use the full openings but how much power is there to lose?
I can cure it bu putting a number of gaskets under the cylinder but then I will loose compression unless ia take away some on top of the cylinder.

Can I take off some material on top of the piston without a problem?
It seems like the easiest way to deal with this.
How much close to the top ring can I go before it gets too close?

[ritzeBijdragerBerichten: 3421]

i also adjusted the crown on the piston, and it had good results.
but that was a 50cc cilinder on a speed engine

don`t know if youre dr will be quiker with that adjustment 😛

like this

De budget beun tjoener: geen geld is te duur of het werkt nog niet
Link naar Mijn collectie / Projecten.

[LastpakBijdragerBerichten: 1129]

unfortunately, a lot of vespa cilinders have bad port lay-outs.
so i’m not suprised, it’s quite common among our mopeds.
the best thing to do is to use a adapter plate as a gasket, or an adapter with gaskets, which makes the piston open perfectly on BDC.
obviously you will lose compression so you’ll have to mill some from the deck.
you must keep a certain value in mind. unfortunately, i don’t know those values, maybe somebody else does?

[ritzeBijdragerBerichten: 3421]

also a reasonable solution but you stil have to modify the kit, the thick gasket needs fixing the top of the cilinder, to make the squish better
adjusting the crown wil be a fast solution without touching the port height and have to mess whith the squish.

greets

De budget beun tjoener: geen geld is te duur of het werkt nog niet
Link naar Mijn collectie / Projecten.

[Gebruiker]

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