'84 700 RPM stays at 3000

Start the bike, it pops up to 3000. Slowly goes down to around 1000 (don't remember). If you put the choke on, it will drop down and stay there and then you can take the choke off and it will idle. When riding, if you go up past 3000, it won't drop any lower than 3000 when you let off the throttle. It'll stay there until you put the brakes on.

I just changed the plugs. Could I have messed up a vacuum line? The throttle looks like is snaps back just fine.

Any advice would be much appreciated.

 

Was it okay before the plug change? Are you certain they are all tight? Sounds like a lean issue.

 

It's a good time to........

check carb mounts for loose clamps or cracks, check that all idle mixture screws are in place and not open more than about 3 turns, synch carbs.:tongue:

 

I think it was a slight problem before the plugs. Not sure. Bought without a test drive.

Was running on 3 cylinders before the plug change. They are tight, was extremely careful installing them.

 

I'll check the mounts. And the screws when i find them.:redface:

 

My $10 bet is that the carbs need cleaning and that the throttle adjust thumbscrew is turned in too far keeping the butterfly valves open so that the carb is running off of the main circuit instead of the pilot and transition ports, and the slides are sticking and diaphragms may be cracked --any takers?

 

You have a vacuum leak. Tighten the carb boots. May need new ones, yours are probably hard as a rock or close to it. You can soften them by mixing wintergreen oil and toulene together and leave them soak in it about 2-4hrs. It works! Don't know how long it lasts though. I've heard several years.

 

Seeing that you did not know before it could be several things. A good carb clean and snyc would be a good place to start. Probably needs it anyway. chances are that will fix it but if not if it were me i would check the valves as well and adjust where needed. I just got finished bringing a zx11 back from the dead. He said it ran great before he parked it 5 years ago. Yeah sure. It was doing similar to what you are describing and after checking the valves i figured out why. Two of the exhaust valves had zero clearance meaning they were always open and a total of 14 valves were out of spec. Some by a lot. Anyways after adjusting them it runs great. Throttle snaps right back with no rpm hang whatsoever.
So seeing as it is a new bike to you i would expect anything.

 

Thanks guys. You've given a lot for me to go on.

 

Changed the air filter. Found all the carb boot clamps were loose. With a screwdriver they were finger tight. Now it doesn't hang at 3000.

A couple of other issues though. I blows a bit of blue smoke until it's warm. After after a short ride it clears up. Valve guide seals?

On start up, it revs to 4000 and slowly drops to 1200. Take just under a minute. Is this normal?

There seems to be a "very" slight stumble just riding around at lower speeds. Almost like it's missing. Any ideas?

At idle, it hunts a little bit. It will go between 900 and 1300 once in awhile.

10,800 miles.