Engine races on starting

I rebuilt the carburetors of my 1981 KZ1100A last year and then took the bike apart to paint. I just got it put back together and tried to start it the other day and it would only start with starting fluid. I saw the WG relay mod in the archives and checked the voltage at the coil - only 8 volts. I did the mod and now have 12 volts at the coil and it will start on gas but the engine races like crazy when it first starts. I hit the kill button and after that it idles and returns to idle normally. I replaced the carb holders last year so I don't think that's the problem. The throttle seems to spring back well and I don't have it open when starting. This is with the engine warm and choke closed. Any ideas?

vacum leak

You did remember to put the springs
back in on top of the diaphrams? (oops)
The slides are all in the down position
when the engine is racing? If not, bad
diaphram,if all stay down it is a vacume
leak.

I checked all the diaphragms and don't see any tears or holes. All the springs are in and it races on start-up when all the slides are down. I also put vacuum caps on the tubes coming out of the 1 and 4 carbs. Where do I look next for a vacuum leak?

The carbs have vent tubes,these cannot
be blocked off or the carbs will siphon
gas past the float needles,this could
be your problem.

tjettim,
I'm not sure what the vent tubes are. The tubes I put vacuum caps on last night are the ones that had tubes going to the vacuum switch near the front of the engine. In any case, doing that did not affect the problem. Is the only other potential source of vacuum leaks through the carb holders?
Lynn

Holes in the diaphragms won't make your engine race. The vents on BS34s will not make your engine race plugged or not. When diaphragms are messed up; either torn or not seated properly, and you open the throttle, there is no corresponding RPM increase because the diaphragms are what pull the slides up because of vacuum. If there are holes or diaphragms are not seated correctly, air gets by the vacuum seal and the slides don't rise... You can check the operation of the diaphragms by removing your airbox or filters and looking at them when you twist the throttle. They don't rise all that much at 4K rpm, by the way.

I didn't initially say anything because I can't quite figure out what the problem is. When you start the bike, you pull the choke out. The bike starts and the revs are at 4K rpm. This is fairly normal. What happens when you push the choke knob all the way back in to where the plungers shut? The thing that I found confusing is the kill switch comment you made. You hit the kill switch and after that it idles normally? What should happen when you hit the kill switch is that the engine should die/be killed/stop running.

OK... if you start the bike using the choke and allow the bike to warm a bit and then push the choke knob back in, what happens? Just trying to figure out if your bike is really behaving normally or there is a problem. Also suggest one of the moderators put this thread in the carb section.

You have an air leak somewhere. I have/had the same problem and I had air leaks around the rubber intake manifolds. I sealed them with electrical sealant, dribbled around the mating surfaces with the head and the probem mostly went away. I really need to pull the carbs and reseal/replace the manifolds. chris3

Check everything.Are the choke plungers operating
correctly? Throttle linkage fully closing? Float
levels after sitting for a while? Ignition timing?
If it ran good before you took it apart, logic
dictates an assembly error.

Thanks everyone for the suggestions. I should have said it wasn't running that great before I took it apart. It wasn't running at all when I got it last year and I cleaned and rebuilt the carbs and replaced the starter to get it running. I only rode it a couple of miles because the steering bearings were really bad and tires had serious cracks. Once I saw that it ran I took it apart to paint and am just getting it back together. Actually the painter still has the tank.

I think wiredgeorge is right - it sounds like normal starting behavior. I didn't expect it to rev to 4,000 when it first started so I never let it actually settle down. I was just hitting the kill switch for a second to keep it from redlining and blowing something up.

Just in case there is an air leak around the carb holders, I took the carbs off today and put a little PermaTex on them. I'm not planning to take them off again for a while.