High rpms

[MikeC23]

Ok, so the bike idles great but when I give it some throttle the rpms take off. I've read through every old thread on climbing rpms I could find but couldn't find a solution to my issue. Here's what I've tried. Removed advance timing rod, cleaned it, regreased it, removed Bob weights, lubed their shafts, and installed new springs (and removed one ring from the springs so there's more tension). Sprayed started fluid around the carb boots to check for an air leak. Nothing. Using the brakes to bring the rpms down seems to work but they won't drop on their own. I've also tried swearing, sacrificing goats to the xs gods, and a little bit of crying. Any ideas?

 

[650Skull]

have you looked at the throttle cable, (lube/greased), or the throttle return springs on the carb, maybe it is sticking or being caught on something when opened up, lube and clean and check for snap back..................Could the throttle hand grip be sticking........???

Replace the new advance springs back to the old Yamaha ones.........

 

[MikeC23]

Throttle cable has been well lubed. I made sure the throttle was rolled the whole way back. I need to order some Yamaha springs.

 

[MikeC23]

I'm not sure if this would have anything to do with it, but I figured I'd look at me carbs. I pulled the float bowls and one of the floats had broke in one side. Also, I noticed that one of my float needles is larger than the other. I'd the needle size difference normal?

 

[XSLeo]

The float valves should be the same size? Yes. Is that your problem, I doubt it. It could make the side with the bigger valve run a touch rich.
A bad float is more likely the cause. With one side broke it can't restrict the incoming fuel flow. This will cause that carb to run way rich. This can cause your rising rpms.
Have you read this? www.amckayltd.com/carbguide.pdf if not you should. Follow the steps to tear down, clean inspect the carb and parts. Most parts are good to reuse. Even gaskets can be reused if not torn.
Once you inspect to determine what needs to be replaced, then start buying just the parts you needs. Carb kits are a waste of money. They have lots of parts that won't work for your bike.
Once you get to the reassembly, follow the guide to adjust things as you go.
Before you buy anything, try to find actual Yamaha parts or Mikuni parts, they are out there, cheap knock offs aren't much cheaper but have much less quality.
There was a thread just the other day about floats. knock offs around $16, real ones for around $20 something.
Leo

 

[MikeC23]

From now on, I'm going to take that advice and only order Mikuni or OEM stuff! I actually have two copies of the carb guide printed out. One on my workbench and one tucked in my Clymer manual!