Easy compression boost

GoldenMotor.com

RLorange

New Member
Jun 21, 2008
127
0
0
Australia
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

Godfather of Motorized Bicycles
Jan 8, 2008
11,837
252
63
up north now
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

New Member
Jun 21, 2008
127
0
0
Australia
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

New Member
Dec 15, 2008
12
0
0
CA.
thanks i used 230 grit and put it back together it dose not leak but i will get the permatex thanks agin !


Rick
 

jasonh

New Member
Jun 23, 2008
1,590
0
0
40
Longmont, CO
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

New Member
Dec 15, 2008
12
0
0
CA.
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.bf. be safe !!!.wee.
 
Sep 7, 2008
188
3
18
Omaha,NE
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.