Had some free time so I did a compression test on the new big bore Dinli, sat at 125 psi, wow, that was low. I ran the mini up and down the street a few times after doing the install and wasn't really impressed with it. So I pulled the head and checked a few things, piston to deck was around .060" [img]i/expressions/face-icon-small-blush.gif[/img], gasket was .020" and raise on head was .028". So overall piston to head clearance, of roughly .108", this sucks. So I shaved the head down to .005", put in the stock head gasket of .012" and let the deck alone. So now with a clearance of .077" I have a whopping 160 psi [img]i/expressions/face-icon-small-happy.gif[/img], and the starter barely cranks it when its cold. I need to take it out and see how it runs. But then again I might just yank the jug and .020"-.030" off it to get a nice quench area.

Anyways, I figured I'd post this because ahile back someone was talking aboutthey did a big bore and it sucked for power, and one of the response's was talking about compression.

 

The reason you had so much cylinder height is that your jug is decked and ported for a 45mm crankshaft. You have a 42mm stroke unless you have an '03 or older engine in your Dinli. You will never get the potential out of the big bore without a major rework (or 45mm crank). It would be actually better to get a 53mm kit that is correct for the stroke. (or again, get a 45mm crank) Be careful with that idea, however, since you already ground on the head. You may have ruined your clearance. Also, remember, compression isn't everything, only part of the equation. Realistically, you want to have your head reworked for the correct squish and dome shape instead of just milling it down. When you take as much as you did off some of the factory heads, you essentially turn them into shape charges, lol! If I can't help you figure it out, feel free to holler back. Ride safe, Ed and crew.

 

Ya, I figured the cylinder height was due to the stroker kit. The head is not the stock head, so I'm thinking that taking the quench/squish area down to around .040-.050" and then lowering the compression to around 175 psi by opening the dome a little might be the route to go.

I'm more or less playing around with this now since my son is out growing it but will keep it for other friends kids when we go camping. It is a fun little quad and great to toy around with (even for a 35 year old [img]i/expressions/face-icon-small-happy.gif[/img])