View Full Version : Is 110psi too low for a cold engine? 89 KX250
crispy
9th March 2014, 09:00
Hey all so when I first bought the bike about 10 months ago, (maybe more) It wasn't running due to a spark issue. While it was playing up i decided to do a cold compression test on it. This was 175-180 psi. Now that I've had it running and riding it a couple of times the compression test has come back at 110-120 psi. Bearing in mind the bike hasn't really had a lot of riding, twice on gravel . once being over xmas holidays and it played, up didn't start after I stopped it. Then last weekend out at Mcleans island for an hour or 2, ran like crap thanks to my s2% fuel I was running. In my mind the fact the compreesion is lower says to me this woud cause hard starting. Any ideas from people?
Akzle
9th March 2014, 16:27
i view compression as more of a yes/no thing. So id say your shits fine.
crispy
10th March 2014, 05:26
Ok, just kicked it over yesterday on the first kick it kicked back, 4th kick it fired up. The issue I have is being the engine has unknown history, other than looking through the exhaust and intake ports inspecting the piston and barrel and giving it a compression test, is when it's warm or been sitting after being run it's a bit hard to start. I thought this was due to engine wear or maybe a float issue. (I did clean the carb out reset the float to factory spec (15-17mm) and now it's got this issue. I thought I may drop it to where it was (19mm) which when it was like this, started on third kick with choke after sitting for 5 minutes.
Akzle
10th March 2014, 05:59
a small 250 kicked back?
You need to work on your technique. Youre probably flooding it.
Dropping the float may lead to starving when youre doing wheelies at wot
Akzle
10th March 2014, 06:09
5 minutes wont cool an engine, you shouldnt need any choke to re start it.
F5 Dave
10th March 2014, 16:35
a small 250 kicked back?
. .
Not much time on motocross bikes huh?
F5 Dave
10th March 2014, 16:37
Ignore compression readings, they are virtually bull on a 2 stroke. You only need some oil puddle (common) to throw up the bore when kicked to root your readings.
Those carbs wear (watch slide & emulsion tube can ovalise) and need a clean out if sitting (pilot etc), but always a new plug when in doubt even if old one sparks in fresh air doesn't mean its good. Powervalve can be an issue on these but this won't affect starting really.
Akzle
10th March 2014, 16:54
Not much time on motocross bikes huh?
no. But ive kicked bigger singles over with no bs.
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