Low compression test results - Honda RC51 Forum : RC51 Motorcycle Forums
 
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post #1 of 9 (permalink) Old 06-12-2014, 05:58 PM Thread Starter
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Low compression test results

I did a compression test on my Rc51. I did it with a cold engine. When I put the gauge in the spark plug section (under the tank with the throttle rolled) I get a compression of slightly below 120. This also goes for the bottom part of the engine, I nearly get the same result. If you look at the compressor tester on the pictures below, you will notice that the results come out borderline.

I would like to pinpoint the exact problem so I can have my local race shop fix it versus having to find out what is going on and then fix it. Money is tight so I would like to save as much as I can.

An idea was proposed that I should do leak down test. Thoughts and ideas? Thanks guys for putting up with me


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post #2 of 9 (permalink) Old 06-14-2014, 12:48 PM
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How many miles are on it? Was it running bad? Why did you do a compression test? When was your last valve adjustment? I would recommend a leakdown test.

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post #3 of 9 (permalink) Old 06-14-2014, 02:47 PM Thread Starter
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Originally Posted by RickyBobbyv8 View Post
How many miles are on it? Was it running bad? Why did you do a compression test? When was your last valve adjustment? I would recommend a leakdown test.

The reason why I did a compression test was because engine got up to 254 degrees when I went to go put gas in it at the gas station. When I got home I found out there was a big coolant leak, my left radiator has a crack and it is not repairable. Also noticed I had a small gas leak, I swapped tanks and did a compression test to be sure. bought the motor with 10k miles on it, not sure if it was races or not.





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post #4 of 9 (permalink) Old 06-14-2014, 02:48 PM Thread Starter
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post #5 of 9 (permalink) Old 06-14-2014, 03:53 PM
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Did you do a compression test on both cylinders? Have you checked your gauge accuracy recently?

04 Nicky
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520 conv. 15/40 RK quick accel kit
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post #6 of 9 (permalink) Old 06-14-2014, 07:14 PM Thread Starter
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Originally Posted by RickyBobbyv8 View Post
Did you do a compression test on both cylinders? Have you checked your gauge accuracy recently?

Yes the gauge works and did multiple tests. Got the same results


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post #7 of 9 (permalink) Old 06-14-2014, 10:29 PM
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120 on both cylinders?

04 Nicky
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520 conv. 15/40 RK quick accel kit
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post #8 of 9 (permalink) Old 06-14-2014, 10:46 PM
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for sure do a leakdown bro. one way to determine if the HG is blown while doing the leakdown, is open the rad cap and see if the coolant bubbles (although it wont always do that even with a blown hg.)
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post #9 of 9 (permalink) Old 06-15-2014, 10:21 AM
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if the compression is the same in both cylinders that is a good starting point. Like the others have said a leakdown is best to see about a blow head gasket
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