Easy compression boost

RLorange · #1 07-01-2008, 12:58 AM

Hey everyone.

I had a problem with a new replacement cylinder which was just over 1mm taller than the old. It came from a new factory so I am guessing that the head was 1mm shorter to compensate however I am stuck with my old head for now. Anyway I found a solution which has boosted compression to beyond my old cylinder.

Firstly I did away with the head gasket altogether! To achieve this I took the advice from some knowledgeable members here and used wen n dry glass paper to shave down both the head and cylinder where the gasket goes. To achieve a flat surface put a sheet of paper on flat glass and then using water gently rub the surface holding flat and firm. I shaved both surfaces flat and then using progressively finer grades of paper got these surfaces smooth as can be. This creates enough of a seal to do away with the head gasket thus boosting compression by making the combustion chamber smaller.

The second thing I did which I don't recommend unless somebody has the same problem was to do away with the bottom cylinder gasket acheiveing the same result of boosting compression. My bike now eats hills for breakfast

Bikeguy Joe · #2 07-01-2008, 06:10 AM

Nice! Soulds like between the gasket removal and lapping the head/jug you got it back to or better than stock.

Did you use any sealer at all on either joint?

RLorange · #3 07-01-2008, 08:13 AM

Just tested it this arvo and boy does it fly! Definitely a bit more powerful than stock! Very pleased with the result. The engine seems to run smoother too am wondering if losing the bottom gasket has changed the port timing for the better.

I used gasket silicone on the bottom but nothing on the head however I sanded those surface baby smooth and dead flat. No leaks after the first test run. Such and easy and effective mod I recommend it to everyone.

shadee573 · #4 01-04-2009, 09:38 PM

have you ridden for more than 10 miles with no sealer ???

Creative Engineering · #5 01-04-2009, 09:55 PM

If you do away with the gaskets, which you can if the surfaces are true, use permatex aviation dope between the surfaces. Do not attempt to polish the surfaces, just get them flat with 80 grit and assemble with the permatex!

Click here

Jim

shadee573 · #6 01-05-2009, 12:30 AM

thanks i used 230 grit and put it back together it dose not leak but i will get the permatex thanks agin !

Rick

jasonh · #7 01-05-2009, 08:56 AM

How's your top end now? Losing that bottom gasket definitely helps the port timing for torque, but I'm curious to see what effects it has on the top end. Could always just do a little porting work to fix that...

shadee573 · #8 01-05-2009, 11:03 PM

Quote:

Originally Posted by jasonh

How's your top end now? Losing that bottom gasket definitely helps the port timing for torque, but I'm curious to see what effects it has on the top end. Could always just do a little porting work to fix that...

The top end is great !! all it wants to do is be on one wheel lol goes up hills at 30+ i was doing 35 up a pertty good hill today !! still no leaks. I want to find a really thin gasket to do that with some sanding and porting. i was thinking about boost porting some1 said they where doing 40mph with that setup!! but i stunt my honda f4i and i know it hurts to fall!!! or get hit at 40 lol

be safe !!!

industrialphreak · #9 01-22-2009, 04:11 PM

I may have to take a look at doing something like this, i know i may be having some issues with compression sealing my header. I noticed even thou i use one of those pounds gageing rachets and never go above 9lbs on the head bolts it seeams one of them may be stripped out. I am going to investigate this a little further i i find the guts to pull my engine off and work on it.