Yamaha Zeal nightmare!!!!!

[erik]

Glad to hear you got it sorted

[Learner Zealot]

I happened across this site while looking for hints on this very problem. come across dozens of theories from different riders (mostly fuel line related). I thought it had something to do with the temp of the engine (it never seemed to happen when I rode at high revs in cold weather) - but maybe my problem is different and just happens to have similar symptoms. It was really comforting to know that someone else has experienced that awful sound and feeling when dropping to lower revs around a tight corner to find almost zero power coming out of it. I just couldn't work out how it could run fine again at higher revs (once over 6 or 7 grand).

Have to check out your solution, even though I have less than no idea what to look for, I can at least steer someone of greater knowledge in that direction. Many thanks. Oh to never hear that sound again!

[RonR]

Good to see Zealot

Have a look at these pics to see what i mean about the sticking throttle slides. (i think that's what they're called). You can tell if they are sticking by lifting a slide up (Slide A) with your finger and releasing it. If it springs back down freely then it's ok. If it stays up then it will need some attention.

When you unscrew the carb bowl (the black cap on the top) you will find a long spring that pushed and a very thin rubber diaphragm. Be careful not to damage this as it is very expensive to replace. My neighbour needed to replace on on an old Yamaha and it cost $180. Now, the spring is meant to freely push the diaphragm down into the carb. I found that it stick on the two carbs on the right. This up and down motion creates a vacuum that draws fuel into the carb. When one of these sticks open it is as if that carb is at full throttle when it shouldn't be. Hence it is not responsive at low revs and only kicks in at high revs. To ensure they slide freely in the carb, give them a light sand with some wet/dry sandpaper. I used 600grit up to 1000grit. Wipe it down nicely and clean it with carb cleaner. Just make sure they slide very freely (not loose though and don't stick even when they are fully open.

If you are successful at removing the screws that uncover the jets on the other side of the carb (these are MEGA tight!) then you can clean out the jets and the whole carb while you're at it with some carb cleaner (CRC Clean-R-Carb is awesome stuff) and compressed air.


Good luck with it. Hope this solves the problem.


J

[Learner Zealot]

Thanks for the pictures, they're really helpful. I presume the throttle slides are somehow stickier when the engine is hotter - I'm hoping that anyway.

It's actually got me interested in taking things apart - which I've always been a bit intimidated by (having no history in it). Could probably get my cousin to help me out. Need better tools first (unless I want to buy new bolts).

Thanks again!