1985 xj 700 revving up on its own.

I bought this bike not running and was sitting for a while. I cleaned the carbs. Now it runs but it revs up like thre throttle is hanging but the throttle is not open at all. Any help would be appreciated.

 

It needs air and fuel to run, running fast means its getting too much of both, from somewhere. All you have to do is find out where - I'd be starting with a careful bench synch.

 

When you "cleaned the carbs" did you break the rack and changed the throttle shaft seals? If not then I will say you most likely have a vacum leak, either the shafts or somewhere else by the intake boots. Of course it could also be that the idle screw is turned in too much.

I'm not familiar with the 85 xj700, but you should have a main screw that opens the throttles to adjust idle rpm, but in order to work properly you would need to at least bench sync the carbs first to make sure they all have the same clearance, the main screw will open or close all of them together, so they need to be synced first.

If you haven't already, I highly suggest you follow http://xjbikes.com/forums/threads/in-the-church-of-clean.14692/ to the T before doing anything else with the carbs.

 

I didn't break the rack. Its not a constant like a high idle. Its like you are reving the bike. It will idle fine. then if I rev it sometimes the rpms hang and sometimes climb.

 

Have you carefully bench synched?

 

That's exactly the symptoms of a vacum leak imo.
I bet on the shaft throttle seal , I've dealt with that with both my xjs, then decided to stop wasting my time trying to cut corners and followed the church of clean to the T.
Those are old bikes, the shafts seal are almost always bad, cracked from old gas vapors, dried up from sitting, then suddenly after a while sitting, we put pressure and movement into a dry piece of rubber that was sitting still for years, it cracks and leak.

You can do a propane test if you have a torch(don't ignite it, just release propane), while bike is idling, check for vacum leak on and around every intake boots, if you hear a change in rpm, the boots are leaking somewhere, do it to the throttle shaft seals too (on both side of the rod holding the butterfly plate) on each carb, if you have a leak this will tell you.

If you don't have propane, you can use carb cleaner or starting fluid, do not use brake cleaner, never ever heat up and breath brake cleaner vapor, unless you wanna have serious health issues.

 

And float set and running sync
Until all these things are done I’d be astonished any non running bike 40 years old runs well.

 

I just benched and synced them. Still the same issue. It will start at idle then just climb up. then if I rev it even higher it will sort of hang at where I revved it. Its not running bad just revving very high without throttle input. I only run the bike for like 5 seconds because its just revbombing the motor when its still cold.

 

I cant really do that because I cant run the bike for long because it revs so high.

 

I have a video of it just it wont let me share it