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
Pothole

Carb issues on '99 YZ400

5 posts in this topic

Yesterday, my bike started bogging pretty bad when I'd crack the throttle open, a problem that I hadn't experienced before. I pulled the carb, cleaned it and blew out alot of the jet ports, and I did the Taffy Mod while I was in there. Before I pulled the carb off, I looked at the timing of the accelerator pump squirt, and it seemed like a good 3-4 seconds. I took the AP diaphram out and cleaned it and put that collar on the AP plunger rod, and now there is no squirt at all, even with the Taffy mod collar pulled off. The AP diaphram looked ok, a bit of rust on the top, but the diaphram itself looked good. Any ideas?

Share this post


Link to post
Share on other sites

I'd say just clean it out the AP pump lines and reinstall everything again. Maybe you put the diaphragm in upside down?

What happenned to me when I cleaned my rod and diaphragm off was that I think I loosened some of the gunk and when new gas got in there it lifted it off and clogged a fuel passage. You probably just need to clean it out again.

Share this post


Link to post
Share on other sites

With the gas on and the line hooked up, twist the throttle many times. You have to prime the pump.

Share this post


Link to post
Share on other sites

You did remember to reinstall the pump spring right?

Also be aware that if the very tiny o-ring washer falls out during installation it creates a venturi effect and the pump bleeds off and won't work either.

You should have 2 o-ring washers in the bottom cap.... 1- large and 1-very small in the pump cover.

Just Checking....

Bonzai :cry:

Share this post


Link to post
Share on other sites

Yep, got the o-rings and the spring installed. Although the bike started like a dream, it started on the first 1/3 of the first kick, even though it was totally flooded with gas from me watching how the AP was working..so that's a good sign. However, what appears to be happening is when I open the throttle very quickly is the gas just kind of boils out of the jet. That seems like there is air getting in there? I've ordered a new AP diaphram, o-rings, and spring..hopefully that will fix this.

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