'82 KZ750 help

Sorry if this is the wrong forum to post this in. It seems like the #1 cylinder on my '82 KZ750 LTD-H3 (19,000 miles) is not firing/running at idle. I've spent the last two days cleaning the carbs, installed new K&L rebuild kits, replaced the fuel and vacuum lines, checked the valve clearances, installed new plugs, checked the float levels and inspcted the advancer. I have a laser thermometer at work and after the bike idles for about 5-10 minutes, #2,#3,#4 exhaust pipes at the collar read about 175-185F and the #1 is about 110-115F. I'm not sure what else to look for. I tore the carbs apart twice to make sure all the jets/ air passages were throughly clean. I checked compression a few years ago and was spot on, and the carbs were sync last year. The spark plug wires and caps are about 3 years old, and I have a nice blue spark at all plugs. The bike runs great above 3500 or so RPMS (the tach is a little off). I'm not sure what to look for now. Thanks!

have you checked for vacum leaks around the intake boots

The boots (from the airbox and carbs) look good. I'll try spraying some carb cleaner around the boots and see if anything happens. I didn't think of that one.

A couple of possibilities.
Missing vacuum cap on the #1 vacuum line ?

Are your carbs Keihins ? if so then you may want to take them off again and check the transition holes. If these are plugged then it may not idle. These things are very easy to overlook. Check out the pic below. I have the carbs upside down in my hand and you are looking into that end which connects to the motor. The throttle flap is open. In the roof you should see one hole from beneath air adjustment screw. Beside it you should see a hole from teh vacuum port. Behind both of these and just where the throttle flap opens (covered by closed flap) are three tiny holes in a triangular formation. You need very fine wire or needle bent at 90 degree to poke through these..not to far...just a little.

I had the same problem as you and it drove me insane until I found the transition holes.

May also be a blocked pilot jet.. but you have gone through the carbs twice so probably not.

If your carbs are Mikunis then I just wasted 10 minutes

:laugh: :laugh:

Let us know how it works out

Yes- they're Keihins. The #1 and #4 carbs have the vacuum lines on them for (I think) emissions. #2 is for the fuel petcock and #3 has the cap. I'm pretty sure I blew out those transition holes, but I'll takes the carbs off again and inspect them.

I keep forgetting that you guys down there have that emmissions stuff. I have no idea how that hooks up or works and wonder if your problem could be there ? I think a number of your fellow countrymen have gotten rid of the emmissions tubing and just capped the nipples - if not hooked up to petcock. Worth a shot ? You could do a search.

The transition holes are hard to get at to blow out. The only thing I found to work was fine wire or pin bent at 90 degree angle.

Good luck