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hey guys,

i just rebuilt my 04 crf 250r,
stock piston
brand new stock 09 head
full fmf exhaust with megabomb
twin air filter cage.

im living at 9000 ft , riding around 7-9000ft.

currently have:
40 slow jet
1 3/4 pilot
158 main

bike only starts by bump, cant get it to kick.. will idle just fine and ride down the road but no top end at all, im thinking im really lean on the main?? not quite sure how much that 09 head effects the jetting

seems to burp a little when i shut it off like its rich, the muffler is super loud and im going to try to repack this week!! maybe thats it??

timing is spot on. brand new plug, compression feels good. spark is good, fuel is fresh.

any recommendations are much appreciated!!!
thanks

. can buy more jets locally.

if the bike was running fine before the '09 head would not have caused this. check and recheck your valve clearances and timing.

ken

hey ken, so i rechecked the timing, the gear on the clutch side and the cam gear is lined up perfectly, valves are in spec, i even have a tool in the spark plug hole that is showing me TDC. problem is the flywheel marks are not aligned properly.. what would cause this? i guess i need to pull the ignition cover back off and see whats going on, but the woodruf key was installed correctly and flywheel torqued with quality torque wrench.

what would cause this? explains my issue as the ignition timing is way off. the marks on the flywheel are about 1/4 inch off of the mark on the ignition cover




SAME PROBLEM THAT THIS PERSON DESCRIBES:
Having an issue with a crf250 '04. After a bottom end rebuild, it's hard to fire up when cold. Valves clearances are spot on the spec. But it's backfiring through the exhaust every so often when kicking it over. It starts with a bump for some reason, and when warm will kick start, but not as easy as we'd like. Ive checked the camshaft timing marks with the right side cover timing marks and it's perfect.

My question is---

When the cam timing marks/crank gear marks are perfectly aligned, why would the 'F' mark on the flywheel (as the manual calls it) be a couple degress over rotated. The 2 marks on the flywheel are both passed the mark on the ignition cover. When timed correctly, should this 'f' mark on the flywheel align with the case marking, or is it a referance that an electronic timing gun uses when timing a running engine? Would this indicate an issue with the timing chain making the ignition advanced (ie sparking too early-backfiring)? Possibly stretched chain? One thing i did notice when refitting the flywheel was the woodruff key was a tiny bit loose. But not to the extent where i think it would allow the ignition to be this far out. One final point, the bike will idle for maybe 5-7 secs, then die out and stall

Any suggestions appreciated
thanks

what cam is in this motor? what is the history of the cam? was it involved in a motor that suddenly seized or had catastrophic engine failure? if so, it's possible the cam gear moved relative to the cam.

i pulled the whole clutch cover off to double check all the gears were on correctly and they were.

the cam is the original 04 crf cam. i thought about the possibility of that being the issue, but like i said the cam and the gear on the clutch side are aligned properly.. the flywheel markings are off

why would the flywheel marks and the crank gear marks not be set correctly?? flywheel has to be spun on the crank or possibly damaged?

the rod bearing came apart in the motor, i had it all apart and rebuilt, bolted on brand new head with old camshaft.

when the engine damage occurred did the motor come to a violent stop? you are checking timing with the cam chain tensioner active. was the cam chain replaced? when you have it at TDC with both the cam and gear marks aligned, cam lobes point the rear, are the all valve springs unloaded? since you say the valves clearances are in spec then i'm assuming this is the case. is the flywheel the stock flywheel?

FIGURED IT OUT!!!!

the flywheel spun over the woodruf key slightly.. causing the ignition timing to be off. now i just need a flywheel puller!!!! banghead.

hope this helps someone in the future.

glad to hear you figured it out. here's a flywheel puller:

http://www.crfsonly.com/catalog/product ... cts_id/624

ken

Out of curiosity, what would cause the flywheel to spin over the woodruff key? I would have thought that the cam gear would possibly slip before the flywheel made it passed the woodruff key a couple mm. Maybe the chances are the same for both in the event of an engine locking up.

Must really be wedged in there, might have a little trouble pulling the flywheel, hopefully not.