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Post by rcorwin3 on Dec 26, 2018 14:06:35 GMT -5
Good afternoon everyone and I hope you all had a good Christmas.
I finally got off my butt and put up one of those temporary garages (10x10) and now I have no excuses.
I recently put in a 100cc BBK and was not able to get it up to any speed. Matter of fact it would lose it. It was suggested that I run a compression test and I did that today. also a friend said I needed to run a wet test. I did that as well.
The dry test sits at 130psi and the wet test sits at 150psi. I have tried to find out what the differences mean but all I could find on YT was auto related.
Any help or suggestion are greatly appreciated and NOT ignored!
Thank you
rik
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Post by jackrides on Dec 26, 2018 14:31:40 GMT -5
If by wet test you mean that you added a little oil thru the spark plug hole, then spun the engine, the oil helped the rings seal better and the oil also took up some space in the combustion chamber. Both increase psi. The throttle was held wide open for both, right? I think there is nothing wrong with 130, but 150 to 170 (+-) is more common.
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Post by SMALL CC TEK on Dec 26, 2018 14:43:22 GMT -5
130 will work just fine ... If the finish in the cylinder was honed better even the cheap ring would seal better .
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Post by rcorwin3 on Dec 26, 2018 15:59:12 GMT -5
Thank you guys and I forgot to do one "little" thing. I didn't hold open the throttle all the way... this is what happens when you become an old fart.
I will rerun the test.
Once again Jack and CC for the help!!
rik
I just went outside to re-run the test and it came out to be 210 with wide open throttle so it should be able to go, right?
Thanks again guys!
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Post by 90GTVert on Dec 27, 2018 7:52:53 GMT -5
210psi is high compression. Should not be the cause of your poor performance. Usually the complaints at that compression level are hard cranking or detonation.
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Post by GrumpyUnk on Jan 8, 2019 14:16:04 GMT -5
I would expect limited fuel supply or clogged jets given the compression test results. It seems a good thing to check is the cam timing as it is very easy to get the cam one tooth off which makes starting the engine a real task.
tom
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Post by jackrides on Jan 8, 2019 14:21:10 GMT -5
Your engine is going to run hot. Be sure you are on synthetic oil. Get a good spark plug reading as a jetting check.
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Post by rcorwin3 on Jan 23, 2019 13:34:03 GMT -5
An update my friends!
Thank you all who offered advice and tips on how I can tackle my issues with the new bike and I apologize for not answering you all right away. I have been pretty sick this past few months but am getting better and have not been able to work on the bike in recent weeks but I just finished up with it this morning after a few days working on it.
I am also going to change my name to dummy. No, to Major Dumba$$. I took the head apart to inspect the BBK and saw that my new cam was upside down. Needless to say it's got lots of power now!!
Once again guys many thanks for all your help.
rik
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Post by pinkscoot on Jan 24, 2019 14:58:44 GMT -5
I guess that's the 4T equivalent to putting a 2t piston in backwards.
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Post by GrumpyUnk on Jan 30, 2019 12:52:17 GMT -5
Dummy:" took the head apart to inspect the BBK and saw that my new cam was upside down. Needless to say it's got lots of power now!!"
Well, I don't think that was the problem. If the cam was indeed upside down, then you would still have had the piston & crank throw at TDC, just on the exhaust stroke rather than the compression stroke.
Remove the cam cover, set the cap sprocket at top, or upside down, and check the timing mark on the crankshaft. Rotate the crankshaft 360. The cam should rotate 180 degrees, or 1/2 turn, leaving the cam timing either at top or 'upside down', depending on where it started. If that does not work, then there is a real problem, except for having the small holes/big hole off a tooth, where the 'off' would be noticeable.
tom
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