XJ 650 Redlines upon Starting

I'm restoring an XJ 650 and started it for the first time after cleaning it up. Cleaned the carbs, cleaned and lined the tank. new plugs, etc. Woundn't start off the bat, so I sprayed some starter fluid into the air cleaner. The engine starts now which is great, but races so fast I have to shut the engine down immediately. Tried to start it 9 times now and same thing each time. The throttle and choke seem to work fine. I figured it must be the carb and will need to take it apart and see what's happening. Wondering if anyone had any ideas or list of things for me to look for while I do this. Appreciate any tips/advice. Thanks.

 

how much starter fluid are you using?

 

I only sprayed it in once and didn't use any more than 1 shot (1 sec.).

 

Did you bench-synch your carbs? Here's a great how-to:

http://xjbikes.com/Forums/viewtopic/t=6 ... ching.html

If that was done, how about wet setting the floats? Couldn't find a link but the info is on here if you do some searching.

If those are done & spot-on then I'd guess you have a major vacuum link between the carbs & the head.

I know you said the throttle & choke seem to work fine but (this sounds stupid) make sure you don't have them reversed.. this has happened here more than once that I've seen. Also, make sure your throttle linkage isn't hanging up anywhere.. this happened to me because I had one of the carb boot clamps rotated the wrong way.

 

I did not bench sync the carbs. I'll check into wet setting the floats and check the linkages. Thanks for your tips.

 

I did this once I had the choke cable and the throttle cable backwards on the carb.

 

For the Plant to High-rev, ... the THROTTLES have to be OPEN.
The Plant NEEDS Main Fuel Jet supplied gas to exceed 3,000 rpm's.

Some very common reasons for High-revving after mounting Carbs:

Linkage stuck open:
• Throttle Cable Connection jammed under rear of head.
• Carbs not fully seated in Manifolds
• Manifold Clamp(s) holding Throttle Linkage open
• Ferrule at Throttle Cable end not fully seated
• Throttle Cable outer sheath "Pulled-up / Not anchored"
• Handlebar Control twisted out-of-position
• Idle Rod Adjustment issue
• Bench Sync way-off. (Use 1/4-Inch wide strips of 3X5 Card)

 

This happened to me the first time rebuilt the carbs on my xj650. The issue for me was that I did not perform the "clunk test" with the carb sliders when I reassembled everything. When I started the bike for the first time after the rebuild the engine redlined every time. I pulled the carbs off again and sure enough I had a stuck slider. Sounds like you may have to pull the rack again, when you do, be sure that the sliders are free to move up and down, they should be fairly responsive. If you have one that hangs, it will definitely cause the over revving issue. Don't give up and be methodical with your carbs, these bikes run so awesome if you take the time to be precise. I had to learn that the hard way.

-Good luck!

 

Check your obvious stuff first. Something is holding your throttle open or you got something goofy.

Easy checks:
throttle linkage held open mechanically
cable bound up somewhere
idle screw way to far in (holding butterflies open)
pistons not being installed properly or sticking - you should be able to push the piston up, and it comes down slowly but smoothly.
needle (on the piston) not seated properly

other things to check:
butterflies bench synced to far open
incorrect jet placement
butterflies assembled incorrectly (backwards/or not lined up) causing binding


also, the squirt of starting fluid might be giving you a bit too much.... try seeing if it settles down in a second or 2