Effing thing!!!!

[DGXSER]

A few issues to look into here.

First for Vile, did you reset the idle screw down?

For both of you, a synch will have thsi effect. Just changing to new spark plugs CAN throw the synch off that much if the old ones were bad.

The other item as mentioned is vacuum leaks. Take an unlit propane torch and move it around the intake boots. If the idle jumps, you found your leak.

[boediddly]

sounds like an air leak I would take the carbs off and inspect the intake manifolds(rubber boots) for cracks.

[vileneeds]

As far as the throttle screw, the other day it idled fine and I have not messed with it. I am balls deep in a carb rebuild for my other bike and the guts are starting to all fall apart. Someone is going to sell me a rebuild kit, hopefully this one has more than just the float,gasket, and a couple washers. SWMBO bought the kit I have now while I was in IRAQ and I think she got rooked. It does not have the O-rings or jets packings for the guts....


The torch idea would be great but I can't make myself let it throw itself into an uncontrolled high idle. I keep hitting the kill switch before it gets to 4600 rpm's. Thanks for the idea. I will tell my guys about it and see what they say.

[DGXSER]

I understand it ran fine at that setting before you put nice new plugs in. Maybe, just maybe it will idle down of you adjust it out, then you can run it long enough to figure out if something else is wrong.

[vileneeds]

I am an airplane mech..... Will new plugs really make that much a diference? If it will I will go adjust it down tonight and try that. Given there are four carbs is there more than one adjustment point for it? I will have to read the manual first on that...... Thank you.

[DGXSER]

Not the synch but the IDLE speed adjuster. On your 78 carbs it should be on the air box side of the carbs, and look notched for a screwdriver to poke in form the side and adjust it.

New plugs COULD make that big of a difference to the synch if the old ones were very worn or one or more was only running part time. It is a bit of a leep to think they would make this happen, but when your at the end of the rope, leep.

[Rasputin]

No new plugs will not cause this to happen. your bike may run better but it definately wont cause this problem. If all you did was change the plugs and nothing else the problem has to be in the cable or the cable sleeve is pulled up onto the top edge of it's support. This will make it look like the throttle cable is moving properly when in fact it is already at the half way open point. It is just a matter of placing it back in its correct position if the cable sleeve has moved. No new parts or any thing else. I would concentrate on the whole throttle linkage before I went to other fixes. If you have changed anything other than the plugs the we need to know about it.

[vileneeds]

Cable will be the first thing I check then as it will require the least surgery. I looked at it earlier and the sleeve looked to be a bit far from the linkage where it terminates at the carb...... might have a winner there.

[Ken Talbot]

When I bought it, all was good. Then it would not turn over; got new sparkplugs. Now it is a one touch fire then revs way up beore I kill it.

Maybe it actually had a dead cylinder or two when you got it, and had been adjusted to compensate. Then, you stick in fresh plugs, all four cylinders come to life, and away it goes!

Or, you might be on the right track with the idea about the cable not being seated properly.

[Ivan]

30 year old bikes are quirky in some respects.

My throttle cable is kinked right near the carb bracket. if I try and straighten the curve out to something more feasible, it hangs on the idle. So, when the bike is back together, I just tug on the throttle cable near the steering head and it idles back down and everything is fine. Weird huh?

Anyway, if you rerouted your throttle cable, that could have done it. check with a flashlight that the idle screw is actually making contact with the stop. If not, then there is an adjustment for the cable near the throttle handle, in the solid part of the cable.

[xs11lover]

Mine did the same thing and the cable was hung up so it was half open at idle. I'm about the 100th person to tell you that.

[vileneeds]

I after I make SWMBO and the kids their breakfast, I will go check again the cable. This time from top to bottom. Thank you guys.

[79XS11F]

Ya, the engine will not just rev by itself. It must be getting added fuel / air for that to happen. As suggested, disconnect the cable and reach in and make sure the carbs are fully closed and start it up. If it still races back the large idle knob back a lot and try again. If still racing ... off with the carbs. Check the linkages between them for proper set up. Look at butterfly valves. They should be open at most the thickness of a bread tie wire. Check the boots and air box stacks for cracks looseness / leaks. check that vac advance is on # 2 carb not #2 carb boot. Check the seal at the boot nipples. If everything looks normal then your going to be into a carb job.
Rob

[vileneeds]

I really hope its the linkage, I do not want to be tearing down both my carbs at the same time.

[fabricgator]

Hello, yea i have the same type of problem except mine starts up and idles somewhat normally and when i rev it up to about 3000 rpm's it wants to continue up to 5-6k on it's own . I suspect that only a total rebuild of the carbs is going to fix it, in addition to syncing and other adjustments. When i ride out on the highway it acts almost like a cruise control ,the excelleration takes the bike up to highway speeds , it becomes a problem though when i want to exit the highway and the engine is still doing 5-6k , naturally i can't put it in a lower gear at such high revs or i could damage the lower gears! I posted this problem a while ago and everyone suggested syncing and carb rebuilds. I took the carbs off the bike cleaned them a bit and generally looked them over, took the bowls off and cleaned them , sprayed carb cleaner throughout in hopes of fixing it , but when i reinstalled the problem returned but not as harsh so i did something right , now when i rev up to 3k it doesn't always accelerate, just half the time now . I did use instant gasketmaker sealing the carbs though so i may have reduced a vacuum leak.

DO NOT Ride this machine until it is operating properly!