86 FZ600S high idle issue

[d2thomas]

Hey all, looking for some advice on what to do / look for to resolve this last issue before I can actually ride my bike (it's been since 2004 since I was able to ride). I first posted here if you wanted some background on the bike.

I picked up this 86 FZ600S Vance and Hines for basically a steal. All it "needed" was the carbs looked over and a new voltage regulator / rectifier. I pulled apart the carbs, cleaned the primary and idle jets, emulsion tubes, cleaned out the bowls, etc. They looked very good - the bike has about 15k miles on it and has sat for the last 3 years. Anyway in addition to that I had to bleed the brake lines, lube the clutch cable, change the oil, replace the fuel lines / filter, get a new battery.....

I get everything back together and get the battery charged. I fire it up and after some gentle coaxing she comes to life. After some tinkering with the idle adjustment she comes in at around 1250, which ironically I later read is the recommended idle. So I grab a helmet and hop on....here is where the fun begins....

As soon as I put it into gear it revs up to 3k RPM and stays there.....WTF? When the bike is idling correctly I can rev the engine and it returns to 1250. I can depress the clutch, does not change the RPM. Only when I put it into gear does the idle change.

Once the idle is up to 3k, nothing can bring it back down. I cannot shift back into N, I cannot depress the clutch, and I cannot turn the bike off and turn it back on.

Any and all help with this issue would be amazing. I told myself I was going to take my time on this bike and enjoy getting it ready but being so close and wanting to taste that wind (after so long missing it) I'm starting to get a bit exasperated.

Advise / ask away!

Thank you!

 

[d2thomas]

Just as an update I changed the oil and it seemed to bring the idle down to about 2500 RPM. Also I can put it into gear and it will stay at the regular idle. If I take it for a spin around the block it will return to the high idle issue however.

Someone suggested a vacuum leak or perhaps one of the slides is stuck open. I'm going to take the air filters off and see if the slides are in position however I wanted to update the situation if anyone could think of what would cause this.

 

[TownsendsFJR1300]

did you check your cable routing and make sure the throttle butterflys are in fact CLOSING?

Have you done a sync on the carbs once assembled back together? This is really important. You'd be surprised, especially with an older bike, who's messed with the adjuster screws and how far out they likely are..

If they are closing and you did do a sync, you can spray carb cleaner around the intake boots and pay attention for any rise in the idle. For the year of the bike, the rubber intake boots are likely rotted causing numerous air leaks.

Someone just found new boots for an 86 fazer with similar issues on this forum. Do a search.

IF, all those pan out, I'd pull the air filter out (or that side with the rubber boot) so you can see down the carb body. You should be able to see all FOUR SLIDES CLOSED at idle. The slides only open after the throttle/butterflys open and they in turn allow more air into the engine. If one is stuck open or not opening like the others (when reving) it'll cause havoc/irregular idle. A rubber diaphram atop the slide(s) with a hole in it or dry rotted will also cause havoc...

BTW, with the aftermarket muffler, you may very well have to richen up your main jet some however I don't believe its causing the problems your experiancing at low RPM's right now...

PLEASE POST YOUR RESULTS...