CRF's Only Forums

Sorry fellas but I'm a newbie here and with the 4strokes

Any suggestions and help is greatly appreciated.
I have 2003 CRF450R that starts well and idles great but as soon as I blipp the throttle it wont idle down and have to use the kill switch to shut her down
I checked the carb,TDC,TPS, and valve clearance are all GTG.Any similar situation or ideas on what this can be??? Thanks!

welcome to CRF's Only! we were all new to 4strokes at one time...so welcome aboard!

several things could be causing it. the first place i would look is the floating valve seal. if you have removed the slide or been using carb cleaner then check the floating valve plate to verify it is in the correct orientation. check the seal to make sure it is in good condition and in the correct orientation. here's a how-to that should help:

http://crfsonly.com/howto/keihin-fcr-ca ... rf450r.php

also check or replace your jets. in fact, if you don't know what needle and jets are in the bike you may want to consider investing in the jd jetting kit we offer. it will dial in your jetting allowing you to eliminate that as a potential problem.

also, check the air boot from the carb to the head and the header for proper installation. also check your hot start nut on the carb. make sure it isn't damaged and verify it's functional. here's a how-to that will help:

http://crfsonly.com/howto/keihin-fcr-ca ... rt-nut.php

report back after you'd done these. again, welcome.

ken

Thanks Ken... Actually my carb slide is rattling right now,I will order a float valve seal and replace it.
The carb boot is in good working condition and so is the hot start as far as the jets go I cleaned them and shot compressed air through everthing... do you think they should be replaced ?

it is very difficult to clean jets. ultrasonic is the only effective way. just because you can see light and or blow air through doesn't mean the orifice isn't reduced. any obstruction or reduction of any size makes a big difference. best to replace if in doubt. if you are not confident about your jetting/needle it may be a good time to swap to a known good solution such as the jd jetting kit.

ken

anyone else have any suggestions as to why this is happening ? I was told my rings were probably worn if so how would I go about doing a leak down test in step by step detail instruction ?
Thanks!

STREETPLATOON wrote:anyone else have any suggestions as to why this is happening ? I was told my rings were probably worn if so how would I go about doing a leak down test in step by step detail instruction ?
Thanks!

You need to be cautious about whom you are receiving advice from. A hanging idle and worn piston rings aren't even in the same ballpark for cause and effect.

Your inquiry on bad piston rings should be investigated first though. I do not believe there is a how-to on leakdown. Try google...

Once you've confirmed proper compression...
For a hanging idle, you have an airleak, something improperly installed, or a malfunctioning part in the carb.

Thanks,124
but yeah thats what the guy meant... is that there was a leak caused by worn piston rings.how often does the piston have to be replaced or serviced ?
Thanks fellers!

STREETPLATOON wrote:Thanks,124
but yeah thats what the guy meant... is that there was a leak caused by worn piston rings.how often does the piston have to be replaced or serviced ?
Thanks fellers!

Better sick the Donald on that guy. Worn piston/rings do not "leak" air - they cause loss of compression from not being able to create pressure and allow oil to get into the combustion chamber which does not equate to hanging idle.

crfsonly wrote:it is very difficult to clean jets. ultrasonic is the only effective way. just because you can see light and or blow air through doesn't mean the orifice isn't reduced. any obstruction or reduction of any size makes a big difference. best to replace if in doubt. if you are not confident about your jetting/needle it may be a good time to swap to a known good solution such as the jd jetting kit.

ken

Ken,

I did as you recommended...installed the parts, started her up and she reved out clean! I have to admit I was a bit sceptical that floating valve seal and the Jd jet kit was going to do the trick... but it did! I just got back from ocotillo yesterday and the bike ran great!!!
Thanks Brotha!

excellent news! glad to hear it's running well!

ken