Compression Tester

[yz250il]

Will this compression tester fit my CRF250R?

COMPRESSION TESTER Big 2-1/2" diam. gauge measures 0-300 pis and 0-21 kg/cm² Screw in proper adapter and snap quick-coupler hose (with attached 14mm and 18mm adapters) closed Also tests cars, trucks and other small engines Clips to handlebars. Includes 10mm, 12mm and 14mm long-reach adapters , 19-3/4"L hose and instructions.

it costs $31.99.

Thanks, Nativ

 

[Masterphil]

Will it fit? Probably.
Will you be able to use it? No.
The bikes auto-decompressor system prevents you from building full compression at the RPM you'll be kicking at.

 

[yz250il]

Well according to the service manual there is nothing saying i cant do the test in fact it's saying that when testing compression it should be 57psi( which is quite low i think so they may have took it under consideration).

it's saying that above 57psi it might be a faulty decompressor cam.

 

[Masterphil]

Sure, you can do it. But it won't tell you anyting about the rings or the valves ability to seal. The best test you can do for ring/valve sealing is a leakdown test.

 

[yz250il]

and i guess there is a special tester for that too?

how is the leakdown test done?

--i can remove the decompressor cam and then i will have the actual test right?

 

[Masterphil]

I'm not familiar with honda decompressor, but if you are able to disable the decompressor, you're not going to be able to kick the bike over unless you are the incredible hulk.

Yep, you need special stuff for a leakdown test, too.

Why are you so hung-up on measuring the compression on your 250f? Your best friend for maintaining a 250f(or any race bike) is an hour meter. Stick to a scedule and replace parts when the time has come. If you race, and keep the bike revved high, you'd be wise to check the valves every couple hours and toss them once you've dropped 3 shim sizes from stock. Once that happens, you might as well check the piston while you're in there, as it'll probably need a new one. Judging by the condition of the piston/rings when you pull them during the first valve change, you can set an hour based scedule for piston/rings replacement.

Yep, you need special stuff for a leakdown test, too.

 

[yz250il]

i have an hour meter the thing is that i just got the bike and i believe that the guy before me did not do any service to the bike.
since the engine was making a small whistle sound from the cylinder head i thought ill shim it and so i did. but then the engine would not idle i had to adjust the throttle stop screw to an idle rpm speed of :2700 which is 1000rpm above the recommended speed in the service manual and it was hard to start - i had to start with an open throttle!

and now after 2 hours of riding the engine wont start.

so i turned to the troubleshooting on the service manual and done step by step, cleaned the carburetor and made sure there is fuel reaching the carburetor.

then checked the spark - was OK(new spark plug)

now it is saying:

"Test cylinder compression, if it's low:
* valve clearance too small
* valve stuck open
* worn cylinder and piston rings - could not be cause i replaced the rings and checked the cylinder and it meets the service limits.

* damaged cylinder head gasket - new one
* seized valve
* improper valve timing - checked and double checked
* faulty decompressor cam"

so now before I'm going to open again the cylinder head and doing any service on the valves i have to check that.

by the way, the bike wont start with the kick starter but when i bump started it there was a big backfire from the exhaust

have any idea whats wrong???? please?!?!

Thanks Nativ :bang:

 

[Masterphil]

Check your valves. Again.
Adjust your fuel screw and slide height to stock settings.
Make sure there is spark.
Make sure the fuel is fresh.

If all the above are good, it will start. Do not touch the throttle when you kick it.