HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
bt08231

idle problem/ carb question...help

8 posts in this topic

Ok before i send this thing to a yamaha dealer, see if anyone can help me figure this out. We picked up an '04 yz450f, the float on the carb was stuck open so it would run it would just pour gas out of an overflow tube. So we pulled apart the carb, cleaned everything and put it back together. It was running before hand and the only setting we messed with was the pilot jet. We also had to remove the throttle positioning sensor but we scribed where it was a put back exactly how it was. Heres the problem, the bike will not run without the choke on. It will not start unless you pull the hot start lever even when it is cold. It back fires alot and acts as if it is not getting enough air. The filter is brand new and clean. I think it may be the pilot jet but am not sure and need it fixed and running strong by this weekend. Any help is greatly appreciated. Thanks in advance

Share this post


Link to post
Share on other sites

I would have removed all the jets to clean it. Possible that some trash is causing this.

The TPS - I would double check those scribe marks - there is another coupler - this is what should be disconnected

I assume fresh gas is being used correct?

Also did the carb get installed correctly with the front and rear boots? No air leaks.

Share this post


Link to post
Share on other sites

Check the TPS voltage according to the procedure in the manual. It may be off enough to cause trouble, although it doesn't seem that likely.

If that's not it, it sounds like there is still an obstruction in the pilot circuit. The choke/hot start combo you're having to run is evidence of that, as this is substituting for the idle circuit. Be sure to check the two air jets at the front of the carb.

Share this post


Link to post
Share on other sites

Make sure you put the slide back in the carb correctly. On the older models backwards looks correct, the 04' models might be the same?

Share this post


Link to post
Share on other sites

Check the pilot jet. The hole in this jet is real small and plugs up if the bike sits long enough. Also check the fuel mixture screw at the bottom of the carb. Make sure its there. I've seen these things fall out from vibration or adjusted out too far.

If you have a shop manual. Adjust the tps or check it. Check your readings at the connector. ( Disconnected) Readings will be in OHMS. You will have a reading with closed throttle and throttle fully opened. Readings vary from bike to bike. Good luck

Share this post


Link to post
Share on other sites

The coil resistance test only tells you if the TPS is OK. Adjusting it requires reading the TPS output voltage with the engine running. The procedure is on page 6-10 of the manual.

Share this post


Link to post
Share on other sites

thanks for all the replies, they will give us a good starting point to figure this thing out. Probably wont get to it until this weekend so i will follow up with either more questions or let u know what it was

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

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
Sign in to follow this  
Followers 0