2005 crf 250r compression test.

[dirtbiker95]

I recently purchased a 05 250r for 2700. The bike is in excellent condition and is still completely stock including the motor. It runs strong and starts first kick. Just to be safe I am going to do a compression test to see how the piston/valves are holding up(valves are in speck). The manual says 57 psi. At what psi should you change the piston/ rings to be safe. For example if I got 47 psi on the test what actions should I take

[dirtbiker95]

Here is a pic of the bike!

[dirtbiker95]

[condor74]

4 strokes don't lose compression like a 2 stroke with a worn ring. If you do lose compression it is more likely be valves than rings. You replace the piston due to wear on the skirt which if it was to gain to much clearance between the bore and the piston could cause the piston to cock and break inside the bore. If you replace the piston and ring you may get a small increase in power but it is nothing like the night and day difference you find on 2 strokes. Go by the hours on the bike. If you do not know how old the piston is, then it would be in your best interest to think about replacing it. Your bike is 8 years old at least, if it hasn't had a piston yet then it is probably over due. I do not ride mx so I plan on replacing pistons every 100 hours or so. Your riding habits may shorten that though.

Congratulations on the new Skoot!!

[dirtbiker95]

The bike was never raced and apparently only has about 50-60 hours on it. I just don't want to spend money to replace it if it is still good. Is there anyway to accurately check if it needs to be replaced besides compression

[condor74]

You can buy a gasket kit and tear it down, inspect and measure. Other than that not really. Now might be a good time to add an hour meter.

[condor74]

The nature of preventative maintenance is changing parts before the point of failure. So by its very definition, you will be replacing good parts. What kind of riding are you planning to do?

[dirtbiker95]

I just trail ride never hit the rev limiter and rarely come close to it. Usually luggging around in 4th through trails.

[dirtbiker95]

The nature of preventative maintenance is changing parts before the point of failure. So by its very definition, you will be replacing good parts. What kind of riding are you planning to do?

I just trail ride

[adam8781]

Experience Has shown me, oem valves will die wayyyy befor the oem piston/rings.

IF its all original, take care of it and keep riding, When the valves die/sack out, you will have to start adjusting/shimming valves every few rides. When that happens, rebuild everything.

Edited June 19, 2013 by adam8781

[JJRace]

compression test is a waste of time with a modern 4 stroke. why? because they have an auto decompression system on the cam.

A leak down test is a much better way to monitor the engine without a tear down.

Inspect the valve clearances, adjust if needed and ride.

[563ripper]

compression test is a waste of time with a modern 4 stroke. why? because they have an auto decompression system on the cam.

A leak down test is a much better way to monitor the engine without a tear down.

Inspect the valve clearances, adjust if needed and ride.

i would dissagree with the first part. the manual still says what the comp should be with the compression release. so if its under spec its low on compression

[JJRace]

or the valves are tight. or on some of the older bikes where you can set the decompression clearance, it would be off.

again a leak down test is what you want to do.

[condor74]

I would check the valve clearance and ride it. Through the summer. If you want you can replace the piston in the winter months. I hear you have colder winters in Canada than we do down here in Southern California. lol Down here I prefer to ride less in the summer and get the good rides in the winter when the ground is loamy and the temperatures are nice.