No compression

[sonic883]

So I broke a piston ring awhile, so I ordered new ones. I put it all together and it ran well, after a few weeks, I got a high compression head and a new cylinder,I took the old cylinder off, and installed the new parts, and ever since then there’s barely any compression, I’ve tightened down the head bolts, and tightened the spark plug,( properly). Just no compression
I am almost certain it’s an air leak. I currently have the base gasket off. It’s a 2 stroke 80cc (66cc)

Pls help

 

[Greg58]

If it has low compression it should run but will be hard to start, the best thing to do is give it a try.

 

[sonic883]

If it has low compression it should run but will be hard to start, the best thing to do is give it a try.

I’ll give it a start up in the morning. I’ve heard of engines sealing well as soon as they run ?

 

[Greg58]

One thing that I just thought of, have you checked the volume of the head? Is it truly a high compression head or not? Compare the combustion chamber of each, the chamber may be the difference.

 

[sonic883]

I

Here is picture of me checking my squish gap, notice the solder taped across piston. Do you see the ends of solder are squished? That's your squish gap, you want to measure that & .028"-.030" is ideal. Roughly the thickness of a credit card. Tape a piece of 1mm solder across the cylinder, then install cylinder head without the spark plug & torque to 12ft/lbs, then grab your rear tire & rotate it to turn engine over a couple times. Then remove cylinder head & measure the squished ends of solder, it should be .028"-.030" or .7mm-.75mm, roughly the thickness of a credit card. If your squish is more than that you wont gain any performance effects of the hi-compression cylinder head

I have 1mm solder, I’ll do a squish check, and let you know. Why wouldn’t it effect performance over 28 to 30 ?

 

[DieselTech]

Heres a example of a good hi-compression cylinder head, it's a 5.5cc combustion chamber.

 

[sonic883]

One thing that I just thought of, have you checked the volume of the head? Is it truly a high compression head or not? Compare the combustion chamber of each, the chamber may be the difference.

It costed about 90 bucks off ebay, it’s the polygon type. Hard to get the bolts on compared to the Stock head.

 

[sonic883]

Heres a example of a good hi-compression cylinder head, it's a 5.5cc combustion chamber.View attachment 160086

Yep that’s the one I have.

 

[Greg58]

You may be sweating over nothing, one of my fastest engines had low compression before I ran it.

 

[DieselTech]

Damn are you across the ocean & had to have it imported? Them heads in the U.S are $48-$50 dollars.

 

[DieselTech]

Are you using the acorn nuts that were on the stock cylinder head? On your new cylinder head?