Help! My bike won't run right!!!

[budsutten1]

I have a 1980 XS850SG. I just took apart and cleaned the carbs. They are all clean, and synchronized. But the bike won't idle right. It's idling at about 1200 to 1300 RPMs. It idles there for about three seconds, then shoots up 1000 rpms for a second, then back down for three or four seconds and continues on like that. I can't figure out why! It has new plugs and wires, but is kinda hard to start when it's cold. Any help would be greatly appreciated!!

Bud

[DGXSER]

I'd check that you do not have a kinked fuel line. Then check the vent to your gas tank is clear.

Also make sure you have synched the carbs with the bike running. Some people think that the bench synching is all that is needed, but the running synch is the one that matters, which you may already have done.

[budsutten1]

Thanks! No kinked fuel lines, and it was a running synch, but I didn't think of the tank vent, I'll check that and see. Thank you! Also, I like your quote. John Lennon!

Bud

[DGXSER]

If John Lennon said it, I never knew that. I thought it was my own.

[budsutten1]

Yea, I believe his exact quote was "Life is what happens while you're busy making plans."

[rpgoerlich]

Did you verify the float levels? If so what they set at?
I cant remember if my SG 's carbs had open pilot jets or if they pull from the main jet. Something to check if it needs the pilot plug in place.

I'd also check for leaks around the carb to head boots and the vacuum caps.

[budsutten1]

I did check the floats. 12.5mm I believe is what they are set at. The intake manifolds are good as well, and the vacuum lines. No leaks. No leaks on the cap either. Any other thoughts?

Bud

[Ken Talbot]

On an XS1100, you can get some idle issues if the orifice in the bottom of some or all of the float bowls or if some of the low-speeed circuits are plugged. When plugged, you compensate during the sync by setting the butterflies open a bit, which causes the idle to hunt all over the place. Without taking the carbs off the rack, take them completely apart, clean them again, and try it again.

[CatatonicBug]

I assume you're running Hitachi carbs on your 850? If so, did you take them all the way apart? The carb bodies split in the middle, with a second gasket, and that is the only way to clean the inner workings.

[budsutten1]

Yup, Those are the carbs I got. And I did take them all the way apart. They do split in the mniddle. I must have went through four cans of carb cleaner spraying and cleaning every little piece. THank you though!

Bud

[budsutten1]

Well it's not the tank vent. I tried it with the gas cap open and no change.
And when I cleaned the carbs, I did take them all the way apart, but did not seperate them from eachother so not to screw up the Synchronization.

[budsutten1]

I also checked the vacuum lines as well and no leaks there. Do I need to take the carbs back apart? I guess I just don't understand what could be making it idle like that.

Bud

[DGXSER]

You say you did not take them apart so as not screw up the synch. Well, by cleaning them, you changed the synch. Anything that changes how effectively each cylinder runs, changes the synch. If you reshim the valves, you can effect the synch. IF you clean the carbs making the mixture better for the cylinders, you changed the synch. If you simply put in new plugs, you could possibly change the synch. To what extent depends on how good/bad things were before the work proceeded.

I only go over this as the issue you describe is often associated with a bad synch. And all to often folks think that if they do not change those screws, they did not effect the synch.

Now, an off the wall thought, not sure if the 850/750 XS shares this issue or not, but the Pick-up coil wires being stretched and broken/just touching, can cause some weird stuff as well.

[budsutten1]

That makes sense. Thank you! And I'll take a look at the pickup coil wires to. Thank you again for your input!

Bud

[soccer4m]

check this

HI, just a quick checklist I didnt see in the other things guys wrote to check
1. change oil, if any gas leaked in it will trigger wierd running, idling problems
2. spray some carb cleaner or wd40 around all the carb intake boots, if idle changes, then there is a vacuum leak
3. check the throttle cable, to make sure its lubed ok, just a slight hangup in the throttle routing can cause engine to speed up with a mere movement of the handlebars
I would change oil first, check plugs to see if any are running rich or lean, spray the carb cleaner around the carb, then check the cable lubing, hope it works out, keep us informed,,,,,,,,,,,,,,Mike in S.Diego