bike idles at 5000 rpm

i have an 81 xj650 maxim, i have removed the carbs several times and completely torn them down to parade rest and cleaned every inch of them, bench sycned them. put them back on the bike, the bike will start but runs at around 5000 rpm and will not come down, linkage is loose, i srayed wd40 to check for air leaks and it did not seem to make a differance. the air mixture screws are all set at 2 1/2 turns out the idle adjustment screw made no differance. and sometimes sounds like a clunking sound from the engine when it is trying to turn over. i would appreciate any help you guys might have
thank you

 

Sync the carbs if you have not already. If you don't know how just ask.

 

i did do a bench sync, followed some directions i found on here using a couple paperclips. when it does run i do hear a loud tapping sound, kinda sounds like a valve tapping, could that be causing the idle problem?

 

If you have already accomplished these steps http://xjbikes.com/Forums/viewtopic/t=2 ... +sync.html as bigfitz describes then you have other issues.

It could be as simple as turning down the main idle screw located middle back of carb rack.

 

also check make sure your throttle cable (s) are seated and ajusted properly

 

ok i will check those things out thank you

 

Mike2301 - - Welcome to XJBikes, and the "inferno" of figuring out the fine tuning.
We simply need more info to give you great advise.
Your bench sync method is in question. You could have a butterfly holding up the works. You need to do a running sync.

http://xjbikes.com/Forums/viewtopic/t=22391.html

You need to do a compression test and check your valve clearances.
You can use a spray bottle on your exhaust to see if a cylinder is firing or not. A dead cylinder is either way rich or way lean. Or not firing.
Hope this helps you. Post up your compression numbers.

 

ok, thank you for the good advice, i will follow the steps you have suggested and post my findings, i love the look and feel of these bikes and hope i can get this one back on the road

 

ok did a compression test and here is what i got #1 143, #2 128, #3 141, and #4 138 also checked my valve clearence and all were in spec accept #3 exhaust was a little bit out at 0.12mm and #4 intake was out at 0.08mm, so i have ordered some new shims to bring those back into spec, Would those 2 valves being out cause that tapping sound i hear?
thank you

 

ok i give up, i have done a valve clearance check, replaced a couple shims, made sure the chain was tight, checked, rebuilt, checked, rebuilt the carbs several times, and still can not get this d*** bike to run right, it eventually starts, but will not hold an idle. i am lost i have no idea what to do, or how to do it, i am seriously thinking of just getting rid of this thing!!!

 

is there anybody in Jacksonville or orange park florida that might be willing to give me a hand? i would be willing to pay some money for the help
thank you

 

5000 rpm is an idle??????

 

Now, maybe I shouldn't be sticking my nose here, but have you checked the choke/enrichment circuit? I've accidently left mine on and had the idle unreasonably high, adjust the main screw and did nothing for it, then I realized what the problem was.

 

Ensure the choke/enrichment circuit is adjusted correctly. If one choke / plunger is slightly open the engine will race.

 

i have checked them and they all seem to be seated correctly and all the way down, any other ideas?
thank you

 

ok the bike runs, it will idle around 1000rpm for a little while, then when i give it some gas, it races up to 4 or 5000rpm and doesnt come down till i turn the idle adjustment screw, but then dies out, i am at my wits end with these carbs !!!!

 

Don't panic, captain, your sucking air, that's if you have done the clunk tests & the cable isn't hanging up.

 

i did follow the steps for doing the clunk test, the slides drop like a rock when the top of the carbs is not on, when the diaphrams are set in place with the springs and tops on, the slides dont drop like a rock, is it supposed to be that way? i did spray wd 40 and did not notice any real differance in idle

 

When you release the twist grip the slides shoud drop with a clunk.
I would test with an unlit propane torch.
I had your prob' with a xj650 & it was the caps on the vac ports, leaked when they got hot.

 

ok, not quit sure what you mean by the twist grip? i will check the caps and see what happens, and i will try the propane thing, would air getting in cause the bike to not really idle? when i can get it to idle at a normal rpm, it only last for about 2 or 3 minutes and then it dies, unless i give it some gas