09-29-2009, 07:28 AM #1
Low Compression Cyclinder #3 @ 22 Hrs
After reading a bunch of threads regarding cam timing I decided to do a compression check as a first indication. The results were #1 - 140 psig, #2 - 140 psig, #3 - 128 psig. This is an 08 RXP-X bought new this year and now has 22 Hrs.
So cam timing is probably o.k. but now concerned about cylinder #3. This is the first time I have done a compression check and the performance of the motor is o.k. 8120 rpm @ 74 mph with 1/4 tank gas. Is it possible that the motor is not fully broken in ? I have riden it hard for 12 - 14 hrs now and if this was a breakin issue I would expect cylinders #1 & 2 to also be low. Is it most likely the rings, valves ? Should I pull the head ?
I'm running a 4 inch intake, worx grate, ros neno TB, intake manifold FA removed, torque plate and just installed JD1 open loop ( 4hrs ), RE block offs, RIVA ride plate, everything else stock.
Any help would be appreciated.
09-29-2009, 07:44 AM #2
- Join Date
- Feb 2006
- Birmingham AL
How did you check the the compression? Did you hold the throttle wide open? did you do it more than once one each cylinder?
09-29-2009, 07:52 AM #3
Yes throttle was held wide open and motor was warm. I repeated the compression test over the coarse of several days and got consistent results.
The first test I did several days ago was with a cold motor and in that case the compression numbers were much closer togather. When I warmed the motor up and repeated the test cyclinder # 1 & 2 improved to 140 psig but cylinder # 3 stayed about the same at 128 psig ( warm & cold ).
09-29-2009, 09:08 AM #4
If you do the test again, you might try squirting a little engine oil in #3. If the compression comes up, the rings a leaking a little. But, it's still less than a 10% difference than #1 and #2. It would be interesting to know when BRP would OK a repair. My guess would be that the cylinder would not have enough compression to fire before they would pay the bill... Ron
09-29-2009, 09:29 AM #5
09-29-2009, 09:31 AM #6
09-29-2009, 09:47 AM #7
Squirted in some WD40 and the compression in #3 came up to 142 psig. I still don't know if it is the rings or valves. The WD40 could have help either problem or am I missing something ?
09-29-2009, 10:08 AM #8
10-02-2009, 11:27 AM #9
- Join Date
- Jul 2007
- PDX - Oregon
Re: Low Compression Cyclinder #3 @ 22 Hrs
Do a leak down test. This will be more informing. You might be able to rent a good quality leak down tool. You'll need a air compressor a well.
My px has a little bit of leak down in cylinder 3.... I guess there was a problem with the X rings from the factory.
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10-02-2009, 06:09 PM #10
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