[pennucci]

my trx250 lost compresion it was running fine yesterday then wen i went to start it today the firts to kicks had good compresion then it lost compresion i took the head off and the piston and cylinder are perfect there was some dirt in there and in the intake cuz my air filter hose wasnt on all the way. i cleaned it all out. what could be wrong with it
thanks

 

[pennucci]

someone told me to check the valves how can i tell it there bad and what should i look for i was thinking maybe some dirt is making one stick open

 

[Helmut]

To check the valves, pour some gas or alcohol, down through the intake and exhaust ports and see if it leaks out around the valves.

Also, it may have jumped time.

 

[Exaviator]

Did you notice if the valve timing was correct when you took it apart. The cam chain may have jumped a tooth or two--especially if it is worn beyond the capacity of the tensioner. Happened to mine, and that will quilt your compression and make it impossible to start.

 

[Exaviator]

Sorry Helmet--missed your comment.

 

[pennucci]

i poured gas in the intake and it leaks out the valves is that good or bad

 

[Helmut]

i poured gas in the intake and it leaks out the valves is that good or bad

That's bad. You either have a bent valve or a bad sealing valve. How bad does it leak? Does it run straight out from under the valve quickly or does it slowly seep out?

 

[94300ex]

since you said it had dirt in the intake it could have gotten some between the valve and the seat holding them open, but like helmut and exaviator said it could have jumped time and bent the valves.

 

[shadetree]

lightly tap the top of the valve spring on that valve..it may dislodge the dirt..if not..you will need to break the valve all the way down.

 

[TRX2fiveO]

You didn't by chance over rev it did you? I know they have a rev limit but you still can cause damage if you hold it in limit too long.

 

[pennucci]

it slowly leaks out of the intake
if i have to replace the valve do i need a special tool and how hard is it to fix valves

 

[Exaviator]

If it only slowly leaks thru the valve, then it may just be that some dirt has gotten lodged in the seat. If you had noticed the setting of the valve timing when you took it apart, that would have gone a long way to solving the problem. Anyway, it it leaks then you need to remove it and check it and the valve seat for damage or wear. You CAN remove a valve without a special tool, but a valve spring comperssor will really make the job easier. Since you have the head off you could take it to a shop for the 20 second procedure, or you can perhaps borrow a tool from a place that has a tool lending policy. Do you know how to do it?? You need to compress the spring and remove the two little keepers that are wedged in betweet the stem grouve and the holder. That releases the valve and it can be pulled out.
To check it for a bend, you can place it gently in a drill chuck and spin it. Any sort of wobble (visual or by feel in the hand) spells a new valve. If OK, then check the seating area on the valve and the valve seat of the head. It should be even and have no blemishes. The valve seat can be lapped with compound to clean it up. You may or may not know this stuff, so I just laid it out for you.
Get new valve seals while it is apart.

 

[TRX2fiveO]

Agree^^^^ to remove the spring is simple. just get a deep socket smaller than the retainer (top of the valve) and set it on top and smack it with a rubber mallett quickly it will pop out the retainer clips, a valve spring compressor is needed to put it back together though.

NOTE: Make sure you install both springs with the tightly wound coils toward the piston. or you will be very sorry, I did it without knowning and it cost me a head, piston, jug, and valves.

 

[ptac]

Suck it up...rebuild the head completely...then make sure you install the timing chain correctly. It sounds more like it is out of time than a leak...with the loss of so much compression....take this from someone that had piston meet valve on his 350X....you just dont want that..:icon_ devil:

 

[Helmut]

Yeah, I agree with all of the above.