Jump to content
Sign in to follow this  

04 CRF450R Will Not Idle - Clogged carb air passage?

Recommended Posts

My 04 CRF450R will not idle unless I pull the hot start lever but it does idle smoothly with the lever pulled. I left the bike in storage for several years with about 1/2 tank of fuel and I accidentally left the fuel petcock open which resulted in bad carb gumming. I rebuilt the carb and replaced all the jets including the pilot jet and thought I had cleaned the carb really well but it won't start without the hot start lever.

 

The fuel screw has the spring, washer and o-ring in place but it makes no difference on the idle. Fuel screw position has no effect, from lightly seated to completely removed the idle is the same--won't idle without the hot start lever. I have to whack the throttle to rev the engine, if I open the throttle slowly it will die. When I do whack the throttle I can see carbon smoke at the exhaust as the bike jumps through the idle circuit--the idle circuit is way too rich. When I release the hot start lever the engine dies as if I hit the kill switch.

 

This is why I'm thinking the air passage for the idle circuit is clogged. Anyone have suggestions for cleaning it or other recommendations for fixing the idle?

 

Thanks in advance for the help,

 

Rob

Share this post


Link to post
Share on other sites

More info: I don't think the bike needs a valve adjustment because it idles smoothly with the hot start lever and the engine only has about 7 hours on it.

 

I'm testing the bike's idle with the airbox removed and just want to confirm it should idle ok that way.

 

Thanks again.

Edited by robrob

Share this post


Link to post
Share on other sites

Sure sounds like a clogged air passage, you can use large-diameter fishing line to clean them out, along with a mild cleaner, like Maxima Suspension Clean.

Share this post


Link to post
Share on other sites

What pilot jet are you running? What altitude and air temperature are you running your bike at?

Share this post


Link to post
Share on other sites

It's the stock size pilot jet and I'm at the same altitude where the bike used to run great. Summer temps are pretty much the same too.

Share this post


Link to post
Share on other sites

Id guess the pilot jet is probably clogged too.

 

You can try this

 

Loosen the carb on the clamps and roll the bottom toward you. pull the bowl and jets and the fuel screw. Use the little tube on some carb spray cleaner and spray up through all the jet holes. Follow that up with compressed air through those same holes. Put it al back together, set the fuel screw at about 1.5 turns to start and see how it runs. The fuel screw will need dialing in, but it should at least idle after that. Oil in the PAJ or MAJ (primary air jet, or main air jet) will make it crazy rich, so the hot start would lean that out and let it run for you.

Share this post


Link to post
Share on other sites

Thanks Shawn, I followed your advice and did everything you said but still no joy. My old slow jet was a #42 which is the stock size. The new jet says #42 also.

 

I picked up the Honda OEM gasket kit and replaced every gasket I could find. I have 3 medium size o-rings left. I replaced the accel pump's d-ring and o-ring, the fuel screw's small o-ring and the large bowl sump o-ring but I didn't see any other o-rings.

 

It idles like a champ with the hot start lever on but dies instantly when it's released.

Share this post


Link to post
Share on other sites

You need to pull that carb and give it a real douche. Not just a spritz with carb spray. It needs to soak in some real carb cleaner and then get blown out with compressed air.

 

Carb%20Dip.JPG

Share this post


Link to post
Share on other sites

Thanks for the suggestion Kah, I'll try pushing some fishing line down the two small passages in the throat near the needle and up through all the jet passages from below. I did follow the Dirt Rider / Zip-Ty Racing carb rebuild article.

Edited by robrob

Share this post


Link to post
Share on other sites

I can't get the fishing line to go through the fuel screw air passage in the carb throat. From the throat I can push it down about 3/16" (4.5mm) into it and pushing up through the fuel screw passage I can't get it above about where the fuel screw threads are--not from blockage just the curved fishing line gets caught. Any suggestions on how to clear the passage other than carb cleaner and compressed air?

 

I can get about 1/2" into the slow jet air passage in the throat so I think it's OK.

Share this post


Link to post
Share on other sites

I can't get the fishing line to go through the fuel screw air passage in the carb throat. From the throat I can push it down about 3/16" (4.5mm) into it and pushing up through the fuel screw passage I can't get it above about where the fuel screw threads are--not from blockage just the curved fishing line gets caught. Any suggestions on how to clear the passage other than carb cleaner and compressed air?

 

I can get about 1/2" into the slow jet air passage in the throat so I think it's OK.

 

Compressed air is your friend. You need to apply compressed air through every oriface of the carb body in every direction possible. Poking things into the carb body is a great way to get something stuck in there for good. Soaking the carb body in the berryman's for 5-10 minutes wont hurt the center gasket which is paper and sandwiched securely between the upper and lower carb sections.

Share this post


Link to post
Share on other sites

Thanks again Shawn, I'll try some more and if it won't work I'll suck it up and pull the carb again and try a soaking.

Share this post


Link to post
Share on other sites

Thanks again Shawn, I'll try some more and if it won't work I'll suck it up and pull the carb again and try a soaking.

 

Dont go nuts soaking, 5 minutes max if your using that berrymans stuff.

Share this post


Link to post
Share on other sites

I tried cleaning the carb in place again with a little carb cleaner down the small passages behind the needle, up the fuel screw hole and slow jet hole. I followed that with compressed air in the same holes plus the two air jet inlets in the intake. I replaced the slow jet with an official #42 from Honda. Still no idle. Does the exact same thing as before, idles good with the hot start lever but dies when released. I'm going to pull the carb and try a soaking.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

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

Reply with:

Sign in to follow this  

×
×
  • Create New...