Question about KZ carburetors

FastDoc · 03-19-2010, 12:22 PM

This is a copy of the message I posted on the KZ owner's forum.

I also wanted to post it here to get your input as well. The bike runs GREAT. I have about 500 miles on it, but I'm having a problem synchronizing the carbs...

Good morning guys.

My name is Bill. I'm a doctor in the Southeast Washington desert. My hobby is car and motorcycle restoration.

I am in the process of saving an old KZ I picked up for almost free. It was abandoned at my friends motorcycle shop when he told the owner it would cost more to fix than it was worth. I got it for a couple hundred dollars.

I had it running in about 1/2 hour.

It needed a battery, carb holders (those were a PIA but I've got it sorted), fork seals, and some small miscellaneous stuff like chain adjustment and spark plugs. The paint and chrome and seat are in near perfect condition. Not quite a 'showbike' but an excellent example nonetheless.

Here's my problem. I have used the search function and did not get an answer:

The idle will not go low enough unless the carbs are out of synch.

I have no vacuum leaks. The throttle cables have enough slack in them. The linkage is free, clean, and oiled. The valves are adjusted, compression is fine. The bike has 6,500 miles on it.

It runs great, but is dodgy when cold for the first 1/2 mile after startup.

Top speed on level ground, in a tuck, is about 85 which seems low to me, telling me there is still something wrong, i.e. carb synchronization.

The idle adjuster is backed out all the way. The fast idle cam is not holding the throttle open. The carbs have been cleaned, new diaphragms and float needle valves fitted.

If the carbs are in synch, she will not idle below 4,000. The only way the bike is ridable is if I deliberately mis set the synch about 2 cm Hg. Then it will idle at 1,200 or so, and fairly smoothly. I think this is because one cylinder is getting too much mixture and driving/being slowed by the other one which is getting too little.

I hope this makes sense.

So, even with the idle screw backed out all the way, she still wants to idle at 4,000.

Please help me guys. I'm bright enough and can't figure this one out.

I really enjoy this bike, and she looks and runs great, but I know she can be better. I'm a perfectionist and I know there is something wrong her.

Bill

03-19-2010, 12:22 PM	#1
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	Question about KZ carburetors This is a copy of the message I posted on the KZ owner's forum. I also wanted to post it here to get your input as well. The bike runs GREAT. I have about 500 miles on it, but I'm having a problem synchronizing the carbs... Good morning guys. My name is Bill. I'm a doctor in the Southeast Washington desert. My hobby is car and motorcycle restoration. I am in the process of saving an old KZ I picked up for almost free. It was abandoned at my friends motorcycle shop when he told the owner it would cost more to fix than it was worth. I got it for a couple hundred dollars. I had it running in about 1/2 hour. It needed a battery, carb holders (those were a PIA but I've got it sorted), fork seals, and some small miscellaneous stuff like chain adjustment and spark plugs. The paint and chrome and seat are in near perfect condition. Not quite a 'showbike' but an excellent example nonetheless. Here's my problem. I have used the search function and did not get an answer: The idle will not go low enough unless the carbs are out of synch. I have no vacuum leaks. The throttle cables have enough slack in them. The linkage is free, clean, and oiled. The valves are adjusted, compression is fine. The bike has 6,500 miles on it. It runs great, but is dodgy when cold for the first 1/2 mile after startup. Top speed on level ground, in a tuck, is about 85 which seems low to me, telling me there is still something wrong, i.e. carb synchronization. The idle adjuster is backed out all the way. The fast idle cam is not holding the throttle open. The carbs have been cleaned, new diaphragms and float needle valves fitted. If the carbs are in synch, she will not idle below 4,000. The only way the bike is ridable is if I deliberately mis set the synch about 2 cm Hg. Then it will idle at 1,200 or so, and fairly smoothly. I think this is because one cylinder is getting too much mixture and driving/being slowed by the other one which is getting too little. I hope this makes sense. So, even with the idle screw backed out all the way, she still wants to idle at 4,000. Please help me guys. I'm bright enough and can't figure this one out. I really enjoy this bike, and she looks and runs great, but I know she can be better. I'm a perfectionist and I know there is something wrong her. Bill __________________ Happy to serve.
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