Need help.... I have and '04 LTZ/KFX400 that is having problems starting. I've checked the coil, CDI, carb and other items for possible reasons why it won't start. I have good spark (new coil). but the compression may be low due to possible broken valve or bad rings. Can anyone tell me the best way to check for compression loss? I've been told to first check compression and then add oil to determine the amount of compression loss to determine if it's a valve or rings. Does this sound right? I do know I have fuel mixed in with my oil. Any suggestions would be helpful.

 

if you have a compression tester, standard is 142psi. if its less than 100 there is a problem.
if you put a little oil in the cylinder and the compression rises than its rings. if it doesnt than valves
but if you have to remove the head for valve work you might as well install new rings or a 440 kit

 

We tested compression last night and found it to be 25psi. Another question that came up was could the decompression on the stock cam be bad and not allowing pressure to build? My guess is no since the pressure is so little, but we wanted to ask the question.

Now the next question is, without spending a lot of additional money, what 440 kit would be the best and where is the best price? I saw someone write on another thread that Trinity wasn't any good.... is this true? What else do I need?.... again someone wrote about a thicker gasket? If I'm in tearing it down, now may be the time for me to add new cams as well. If you change both, do the aftermarket still use the decompression or not?.... again, which ones are good and where can I can the best pricing?

Thanks for the input Mucky.... I do appreciate your help. Any other advise would be great.

 

How did you test motor compression? 25 psi seems like a large loss, could be cam, timing chain issue. 25 psi would be a pretty big hole in piston or maybe even blown head gasket, or even cracked cylinder. How did it die? The fuel mixed in oil points to hole in piston, though.

 

I had it in the shop to discuss with them the issues and to get any suggestions. To start, our pressure test probably wasn't correct since we didn't do the test with wide open throttle. Now keep in mind I'm not an expert on the internals of the engine.... this I will admit. But the good news is I am learning alot.... especially about tearing this quad apart over and over. Anyways, according to the shop after hearing it, he believes it's in the valves or possibly the cam decompression. He said it's not uncommon for one of the springs on the decompression to break. His other thought is that it's a vavle clearance problem even though I had it adjusted not to long ago.

For now I wait until the shop can make their determination. If they don't find a problem, I start pulling it apart to see how the piston looks. One thing is for sure, the engine is not cranking with full compression.... after riding it for 2 years you get to know the sounds of the machine and when it first happened I could tell there was a difference.

I appreciate eveyones efforts in helping and as always, your advise is being taken into consideration.