KZ1100 spits and won't idle

I am resurrecting a 1982 Kawasaki KZ1100 with about 11,000 miles for a guy in town. It ran fine 9 years ago when he parked it w/o proper storage steps.

Because the carbs were so welded and I lack rebuilding experience, I sent them out to a local, independent shop who everyone trusts and has been in business many years. He purchased a kit, rebuilt, and adjustments were 'set to factory specs'.

Here is my stupid mistake that I own up to. I mistakenly told him that it was a 1000J and he rebuilt accordingly, but the 'J' main jet is very different. After I learned my mistake, I consulted him (he still had the old brass), and doesn't think that he changed the needles. I tried researching the difference in kits and can fine only the main jets are different. I reinstalled the original jets after insuring the ports were clear leaving the rest alone.

For the most part, the bike starts right up, runs good at mid and higher RPM's, but won't idle and spits when it tries. I finally got it to idle by cranking up the idle speed multiple turns, but then it wants to continue revving high, may eventually drop, but a short time ago, it remained revving at 4500 RPM and I shut it down. I checked the plugs and #4 was a bit wet, so I leaned it's idle mixture 1/8 turn. The rest look good.

I checked, adjusted, and rechecked the valves and are within specs. New plugs and air filter. The rubber between the carbs and engine are in surprisingly good shape despite the age observing no cracks, but I didn't remove them. I tried to keep it running long enough to sync the carbs but gave up; even so, they aren't crazy out of spec but will need to be synced if I can get it to idle.

Compression check hot and cold: 125 to 130, except #3 is 90. Yea, I know. There is the slightest oil leak in front near #2. While trying to sync, I noticed a vacuum drop from #2 during a 'spit', but I don't think that's the only cylinder spitting. Anti-pollution reeds checked good for what that is worth. The tank had a lot of rust, but I cleaned that and inserted a see-through fuel filter to verify that crap isn't getting inside.

I'm tapped out and am throwing this out there: why won't it idle?

Rpm hanging and won’t idle. Air leaks and it’s running lean. More than likely the carb boots. Get a midrange price set from a reputable company. The cheep $40 sets off evilbay bay are junk. A decent set will be in the $80-$90 range.

Your low compression on cylinder 3 tells me that you need to check your valve clearances. This should be one of your first steps.

Is the airbox installed along with filter? Assuming yes, then it sounds like the carbs are still not properly clean.

This may help...
zeus.mtsac.edu/~cliff/storage/gs/Mikuni_...Rebuild_Tutorial.pdf

I've checked #3 twice now and it is good.

Yes, airbox is installed and is stock.

I started it, got it to idle somehow, and tested 29 year old boots between the carbs and the block. RPM's dropped when sprayed where the boots meet the block, not the other side, and no effect on the 29 years old rock hard boots between the air box and the carbs.

I expected a rise in RPM's instead of a drop.

There is your answer, replace boots they are letting in air causing the erratic idle.

I ordered boots/rubber for both sides of the carbs and will see if that takes care of it.

New boots on both ends of the carbs definitely solved the idle problem.  Once idling, I then synced the carbs and it runs better than it has so far.  I test rode it and it's still a little rough, but with 90 lbs compression in one cylinder, I think I have done about all I can short of a rebuild.

It still gives some indication of a slight vacuum leak, so I am going to disconnect the 'clean air system' (in the manner described elsewhere in this forum) as soon as I find a hose and see if that helps.

Hopefully you’ll get lucky and compression will get better. The rings might reseat, as long as the compression issues is just from sitting. 

wrote:

Your low compression on cylinder 3 tells me that you need to check your valve clearances. This should be one of your first steps. 

Your suggestion to check valve clearances tells me you need to read the OP again, this time more carefully. Hint: that WAS one of the first steps.

I know you guys are incredibly eager to tell people to adjust their valves, but you could at least try to be reasonable about it.