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

 

[sonic883]

Yes, the engine should have enough compression to lock up the rear wheel when you push it. My rear wheel skids in the gravel for a bit when I let out the clutch to start the engine. Is your clutch slipping?

Just replaced the clutch pads just before this problem, definitely not slipping,I have the clutch cover off so I can see the pad is not slipping.

 

[sonic883]

Yes, the engine should have enough compression to lock up the rear wheel when you push it. My rear wheel skids in the gravel for a bit when I let out the clutch to start the engine. Is your clutch slipping?

Just replaced the clutch pads before this problem, definitely not slipping. I have the clutch cover off so I can see the pad is not slipping.

 

[Greg58]

How long did you run the rings in the first cylinder? Was the bore of the cylinder damaged? If so the rings are probably going to take a good while to seat, if they seat at all.

 

[DieselTech]

You need a base gasket, unless you siliconed it.

 

[sonic883]

How long did you run the rings in the first cylinder? Was the bore of the cylinder damaged? If so the rings are probably going to take a good while to seat, if they seat at all.

A few long rides…

 

[sonic883]

Ok guys, I made a base gasket with a cereal box, because my other one broke. I also changed the head gasket. And it made a big improvement, it has a lot more compression , there’s a quite a bit of resistance, but I’m not sure if it’s enough to run, don’t think it’s the compression I once had. Can you run 2 strokes with low compression?

 

[DieselTech]

Have you checked your squish since you have done all this engine work?

 

[sonic883]

Have you checked your squish since you have done all this engine work?

Sorry, what do you mean by squish ?

 

[DieselTech]

Give me a minute & I'll try & find a picture of procedure of checking squish, if you installed a hi-compression head you wont gain any effects of it without a proper squish gap.

 

[DieselTech]

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.