[crf-mat]

Hello,

Have a 2004 CRF250X that I have had for about 7years, have only done a handful of rides a year at max on local trails and have always changed oil, oil filter and cleaned/changed air filter after every ride and fuel drained (generally 50-100kms per ride). Last rode 6months ago and had some challenges starting it - took a tiny bit of throttle to get it to fire. Was also struggling to idle when pulling up to a stop, took a steady throttle to keep it started. Long story short, thought it was time to have another look at valve clearances as every thread on these with problems starting tend to be this.

In the workshop, did a compression test and it showed 25psi. Thought the gauge also had a leak so verified it again with a different gauge and got the same low result. Pulled off the cover, set TDC and checked clearances, adjusted shims to get it into spec and put everything back together - still wouldn't start. Did a compression test, was still showing 25psi. Put some 'start ya bastard' down the spark plug hole and tried to fire it, got close but didn't kick over. Have confirmed spark and was also using a jump starter to ensure really good power. Tried putting a small amount of oil down the cylinder and rechecked compression and it only increased 1-2psi (so assuming it isnt rings).

At this stage we ruled out most obvious things and thought it was time to pull off the head and have a look. Head gasket looked ok (no obvious leak) and we did a bench-test with a small amount of fuel to see how quick it passed through the valves which it was quite slow (10-15mins for it to pass through) which seemed in line with other bikes we have done the test on.

Other than throwing a new head-gasket on and trying another pressure test to see if any improve I am kind of stuck as to what to check next. Any ideas?

Cheers,
Mat

[Leardriver]

A plugged pilot jet and maybe the passage above the jet into the carb.
Replace the jet, don't try to clean it, and use some carb cleaner and compressed air up into the pilot passage while the jet is out.

[Aussiecrf230]

Is the decompression device adjusted properly.
What sort of readings did you get for valve clearances before reshimming?

[crf-mat]

A plugged pilot jet and maybe the passage above the jet into the carb.
Replace the jet, don't try to clean it, and use some carb cleaner and compressed air up into the pilot passage while the jet is out.

Think it is worth having a look at the carby, would there be any obvious signs to look out for if this was the issue?

Is the decompression device adjusted properly.
What sort of readings did you get for valve clearances before reshimming?

The decompression mechanism on the carby looks like it is working properly, factory spec says 59psi should be the reading to compensate for it. The valve clearances were quite a bit off on intake, think one of them went down 3 shim sizes, and one of them down 2 shim sizes.

[Leardriver]

If a bike won't idle without the choke on, a plugged pilot is almost assured. It can also cause horrible drivability problems at mid throttle.