I just picked up an 86 ZX6R. It starts easily but once started the engine surges up to 4500 rpm and then drops back down to between 2000 and 3000 and periodically surges back up again. This is all without touching the throttle once. It seems to settle down after a few seconds but if I touch the throttle even slightly it sputters out. Same result if I apply choke.

The previous owner said it did that for him and after idling for a bit it would settle down. I haven't let it idle very long yet to see if that is true. Anyone know where I can start looking to figure out why it is doing this? I assume its dying when I touch the throttle as it hasn't warmed up enough yet but that is just a guess.

As a side issue the previous owner hard wired a toggle switch up on the upper cowling bracket to turn the fan on and off. Is this normally controlled by a sensor or does the fan normally run all the time.

And last question ... stupid one I am sure ... The key has four positions. Off, second, third (where all the lights come on and I can start it) and fourth. Can anyon tell me what the 2nd and 4th positions are for??

I've always owned cruisers so this is new for me. Thanks!

 

Welcome to the forums....

Should have lock, off, on.... Not sure on 4th position.

When the bikes warmed up, she runs good? No probs?

 

Thanks, I figured out what the positions were. Lock, off, on, lock with rear brake light on. At least according to the local dealer anyway.

I fired up the bike alst night and let it idle for a bit. As it warmed up it started surging up higher more regularly so now I'm thinking that I may have a carb stuck open or something somewhere as that would explain why any touch on the throttle shut it down. I guess I'm going to have to pull the carbs and give them a good cleaning as soon as I can dig up a maintenance manual. I'll probably check the fuel pump and throttle cables while I'm at it. After that we'll see.

It starts quickly enough though.

 

Ya, I would bet dirty carbs. And check the carb boots while you are there. I had a boot that was leaking on me, and it caused a similar prob.

 

I've had that issue on my Shadow although it didn't make it rev, it made it stumble. Badly.

I'm probably going to have to synch the carbs as well. I guess its time to bite the bullet and get a manometer.

 

You're all ready that far into, might as well...

Gl man, let us know how it turns out.

 

look for air leaks in the carb boots or intake seal. could be a slight leak. and the carb cleaning will probley help too.

 

As a side issue the previous owner hard wired a toggle switch up on the upper cowling bracket to turn the fan on and off. Is this normally controlled by a sensor or does the fan normally run all the time.

Yes, normally controlled by an automatic switch.


edit: A switch is a switch, so the previous owner made it a dedicated manual switch. Do you have enough attention dedicated to turn it on at the right time?