09 crf150r big wheel erratic idle

Hi everyone. Whenever I start up my girlfriends bike, the bike will idle high and randomly and slowly go to a normal idle rpm. If I play with the "idle screw" it has no effect on it at first then will drop to low and die. The problem seems to be not as severe when bike is warm after riding it. Went threw the carb and checked valve clearances and jetted for altitude (Iowa) this winter. Any one have this similar problem??

PS: bike take 10+ kicks when first starting in morning and when engine is warm it will start within 3 kicks

Air leak, clogged pilot jet, hot start sticking, incorrect idle adjustment, valves are not in spec (checked not done correctly). Do you have good spark?

Hard starting is a lean (air leak) problem 95% of the time. Worst case is a valve seat leaking. After your rejet, did you tighten your boots back up??

Edited by weantright

I did tighten the boot clamps up. Any trick on how to check for air leak? Would starting fluid sprayed along air box tubing to see if engine rpm increases be a good idea?

Yes use starting fluid to check for leaks.

What is your jetting?

Did you adjust the idle?

Stock jetting except for a 45 pilot I believe

Jetted for altitude in Iowa??? Research jetting a bit more. Cold and dry in Iowa would call for richer jetting. Summer will be warm and moist and jetting may change.

Stock jetting with 45 pilot is ok for where he rides until he climbs north of 4,000 ft. Sure there will need some air screw adjustments but jetting components should not change. For better running bike a leak jet change and AP mod is a must but the bike should still run. I feel the issue if not an air leak, is air screw and idle are incorrectly set for the hanging idle. Hard starting would indicate either valves or air screw out of adjustment and since both are happening I would look into the low end fueling circuit. Start by adding fuel via air screw a 1/4 turn and see what happens. If you feel the air screw is correct then drop the idle an 1/8 turn.

It takes 15 minutes to recheck the valves, its easy to overlook where the stroke is making measurement off.

Thanks for all the help guys will be checking everything over tomorrow. Does anyone have the link to the ap mod? I have done one to my buddies yz426 but it wasn't an o-ring mod

OK so I re checked valves, they are in spec. Checked for an air leak and found none, took carb apart, blew all passages out with compressed air. All o-rings and gaskets were not leaking or seeping and it still has the weird idle. I'm lost on what to do. The bike will stay revd up then slowly drop down to a low idle randomly and sometimes won't drop down. But when it does it goes so low it'll die. I've never had a bike give me so much Hassel as this 150. Anyone have any other ideas or had similar problem?? Help

Proper play in the hot start cable and throttle cables?

Did you pull the pilot out and blow compressed air though it and hold it up to the light to make sure it's clear??? What size is your pilot? What size is your leak jet (for starting)?

So after burning my hand on the header and some checking over everything I found that there was an air leak it the rubber connection from the air filter to the carb. Ordered a new air box and just put some silicon as a quick fix over the hole. Bike idles great! Thanks for everyone's help. I do have a.question though. The bike has a rekluse clutch on it. When crawling at a slow speed and brapping the throttle the bike will die when the rpms come down

Only does it when moving slow and is unpredictable when the bike will die. It doesn't seem like the clutch staying engaged. Will boring mod help with this?

What is the boring mod??

If the recluse stalls when a quick throttle close happen it is either a incorrect clearance in the clutch disc, grooved basket, idle setting or low end fueling not adjusted correctly. Rekluse on this bike need perfect low speed jetting otherwise stalls will happen. Idle should be set at 2200-2400 (just starts to creep) for good overall performance.

Dang auto correct. Meant to say o-ring mod not boring mod haha

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now