2003 cr250 ???

[randytbo]

i just got my first 250. i have been reading and it sounds like i have a pre-ignition problem. it doesnt to it all the time. i noticed when i was running down the road at about 3/4 throttle i could hear a little rattle in the top end, kinda like little metal peices ratling around. pre-ignition?? also when i open it up through the gears and then slow down and pull the clutch it stays revving high and slowly comes down. could someone tell me whats going on. im not running it anymore untill im sure.

[mbosma]

Sounds like it might be an air leak somewhere. Can you do a leak-down test to check your crank seals and gaskets?

[randytbo]

do you have to split the cases to change the crank seals?

[fordmugg]

sounds like its pinging .....it would happen to my 2 stroke when i was in glamis ....what gas are you running and what jet is in there

[randytbo]

Originally Posted by fordmugg

sounds like its pinging .....it would happen to my 2 stroke when i was in glamis ....what gas are you running and what jet is in there

i am running 91. it has a 390 main, 30 pilot, 1.5 turns on the air screw, 2000 ft elevation and a pro circuit platinum 2. it doesnt rev up on its own. it only happens after its been running for about a half an hour. ill open it up on a road and when i slow down it wants to keep revving for a while.

[randytbo]

does anyone have any ideas? does this setup sound right?

[nutty]

Like mbosma mentioned, it sounds like a air leak. A leakdown test would find your leak if there is one. I built a leakdown tester for $12 from home depot parts. The crank seals are easily replaced by taking off the right side case cover and pulling your stator cover and stator on the left side.

[randytbo]

i havnt done the test yet but i will when i get the parts to make a tester. but does anyone think a real lean condition will cause this problem. it has a 390 main and i am thinkin it should be bigger i have a pro circuit platinum 2 and vforce reeds. im thinkin i should have like a 410. any input on this?

[bikepilot]

A lean condition can definitely cause that. I've not had a case-reed CR, but on my '01 390 would be too lean at your elevation. I ran a 420 at sea-level so a 410 is probably about right at 2k feet. I run a 390 (I think, it might be a 380) in the rockies (which seems just about ideal for 7-8k feet - its a touch lean at 6k and definitely too rich by 10k).

[dklassen]

Jetting that bike is tricky and since your from Alberta I would have to think that colder temperatures are in play at this time of year. I haven't been out this month and my 06 was working well in 25-30 C temps in September. I wouldn't even want to start it now that its only +5. You should richen the bike up by 2 sizes so go to a 410 main (or possibly a 420). You'll have to adjust your air screw. One last thing is to try Esso gas. I know this sounds a little weird but my bike was pinging like crazy on Shell V-power which I thought was a good fuel but I was told to try Esso premium and the pinging went away. Even without the octane booster that I was using with the Shell gas. Try these two things and see how it works. It's a cheap way to start.