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

 

[Cisco]

Thanks @DieselTech , now I need to take a squish measurement on the engine with the CNC head. Chalk it up to inexperience. I bought into the advertisement hype about improved performance and power. This is an example of bolt-on upgrades. I didn't know about squish and how it may effect performance. I've learned that you can't just slap on a 'High Performance' part and expect it to work as advertised ;-)

 

[DAMIEN1307]

Thanks @DieselTech , now I need to take a squish measurement on the engine with the CNC head. Chalk it up to inexperience. I bought into the advertisement hype about improved performance and power. This is an example of bolt-on upgrades. I didn't know about squish and how it may effect performance. I've learned that you can't just slap on a 'High Performance' part and expect it to work as advertised ;-)

Hence, one of the reasons i stay with stock builds and can help stock builders as well...I leave the HP mods etc to the big boys here in the forums with experience in these realms...Too many different actions and reactions to modifications making for other modifications to make the existing ones work...lol...DAMIEN

 

[DieselTech]

I'll help when I can, I got the cases split on one right now, trying to build one from extra parts.

 

[sonic883]

I'll help when I can, I got the cases split on one right now, trying to build one from extra parts.

I was just wondering, with the carb on does it create more compression? I didn’t have my carb on just the intake when I tested it.

 

[DieselTech]

That I'm not sure on, I could see if you are running reeds it could affect compression. That's a question I do not know, maybe some of the pros will chime in on that. So we both will know.

 

[mony0_3]

I was just wondering, with the carb on does it create more compression? I didn’t have my carb on just the intake when I tested it.

Compression starts when the rings pass the exhaust port.

 

[Greg58]

If you’re doing a compression test with a gauge you open the throttle so the down stroke of the piston can draw in the maximum amount of air to get an accurate reading, so no carb no problem.

 

[Chainlube]

You're not going to get a very accurate reading unless you can spin the engine a few times in quick succession, your 50-60 is probably good with just rolling the bike.

I was just wondering, with the carb on does it create more compression? I didn’t have my carb on just the intake when I tested it.

You're good with just an open intake.

 

[Chainlube]

You're not going to get a very accurate reading unless you can spin the engine a few times in quick succession, your 50-60 is probably good with just rolling the bike.

You're good with just an open intake.

A drop of oil in the cylinder before you do the test will help the results.