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Post by 926am on Feb 27, 2017 17:25:05 GMT -5
Hello, can anyone tell me what is the proper compression when cranking? Manual says 231psi, but that seems high (more like running.)
I am currently at 50psi when cranking (cold.)
Thx.
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Post by crawford on Feb 27, 2017 19:52:17 GMT -5
to support fire you should have no less then 125 psi. You should first check your you valves and rocker arms. You compression seems way off what you manual saying. my Ice bear 300 cc was only 180 psi new. working on car and trucks never saw a gas engine have the high compression either.
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Post by rockynv on Feb 27, 2017 22:54:16 GMT -5
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Post by dollartwentyfive on Feb 27, 2017 23:40:48 GMT -5
from an '  -'  CH250 elite service manual: 184 +/- 28 PSI. perform this test at WOT. squirting some oil into the cylinder, then spreading it by cranking, you can tell if it's the rings that is causing the low compression. other causes could be misseated/cracked valves, blown head gasket, or cracked head. |
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Post by crawford on Feb 28, 2017 10:00:43 GMT -5
Remember this isn't a Honda it's china right or did I read his other post wrong?
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Post by 926am on Feb 28, 2017 11:31:50 GMT -5
Yes, Chinese made. I'm having start problems and have ruled out everything eles. Compression was the last test. I have all the necessary gaskets for a rebuild, but I just wanted a second opinion on the numbers before tearing apart.
Thx!
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Post by rockynv on Mar 1, 2017 12:56:24 GMT -5
Still a 10.5:1 to 11.0:1 compression ratio and thats what really matters. The spec is with the engine warm not 24 hours sitting cold so it may appear high to some.
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Post by 926am on Mar 5, 2017 16:04:00 GMT -5
Ok, so I got everything apart and it looks like the rings had all oriented themselves so the gaps were lined up. I know I didn't install that way, is it possible they moved on their own? Bike ran for most of the summer, but I rarely went more than a mile or two.
Could this be indicative of a problem? (Everything, piston, crank, head was new.)
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Post by rockynv on Mar 5, 2017 20:20:45 GMT -5
Is the bore out of round? I have seen this happen on an egg shaped bore on the worn side but its not very common and you should have been using a quite a bit of oil.
Did you put a good cross hatch on the cylinder with a hone before you put in the new rings?
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Post by 926am on Mar 6, 2017 17:31:39 GMT -5
The cylinder is the only part I didn't replace. I'm ordering a new one w/piston (265cc) which will hopefully work well with the 32mm carb & straight through muffler.
It's so odd, every ring was exactly lined up at the gap, like it was done intentionally. I had some over-heating problems, and I bought it used (7,000mi) so who knows...
I noticed the cam chain isn't perfectly aligned with the chain guides. Is this normal? I can't figure how to correct (unless I have a defective camshaft.)
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Post by dollartwentyfive on Mar 6, 2017 23:06:56 GMT -5
Still a 10.5:1 to 11.0:1 compression ratio and thats what really matters. The spec is with the engine warm not 24 hours sitting cold so it may appear high to some. yes, the specs i posted was for a cold engine. either way, it's obvious 50 PSI is way too low. |
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CH250 elite service manual: