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Discussion Starter · #1 ·
hi all im BONE...i have a 1977 z650...have rebuilt engine,,just had carbs professionally cleaned and rebuilt..also electronic ignition fitted. when i get it running its smooth as a kitten, when its warm will start straight up. then when its cold it dosnt want to know.....any ideas PLEASE
 

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Hi Bone,
Can you tell us a bit more? How long does it have to sit before cold starting becomes a problem?
You may want to consider, dumping all fuel and filling it with fresh fuel from a reputable fuel company. And get non-ethanol fuel if at all possible. It is worth the extra few pennies per liter.
 

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I had a friend who would lean his bike all the way over in cold weather to get the carbs to leak into the intake. Started up all the time when he did that. You may want to check the choke adjustments to make sure they are choking the bike enough. Make sure you have the Factory Service Manual, not the Haynes or Chilton, they really suck. IMHO ;)
 

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Some bikes are notoriously cold-blooded and don't like to start after they sit for a week or more. My 1982 Honda CB900F was like that. If you rode it every day, it was pretty good, but if you let it sit for one week, man oh man, it was hard to start.
Some of the ninja 250 bikes were similar.

I think what contributes to the cold-blooded nature is super lean jetting to meet emissions regulations.

You could try checking the choke as suggested by Kawasakian and also check the setting of the air screws.
 

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OP reports that bike only has to sit for a day or even just a few hours and then it is hard to start.

I don't recall the KZ650's of that era being cold blooded, so based on the these two facts, I think we can rule out OEM cold bloodedness.

Check for vacuum leaks, including the choke. Check the air screws. Check the float levels and clean the carbs. Make sure the air filter is clean. Also have you checked valve clearance? Did anyone forget a rag in the intake somewhere?
What is the engine compression like?

Also suspect is the 3rd party electronic ignition conversion.
 

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Discussion Starter · #6 ·
Hi Bone,
Can you tell us a bit more? How long does it have to sit before cold starting becomes a problem?
You may want to consider, dumping all fuel and filling it with fresh fuel from a reputable fuel company. And get non-ethanol fuel if at all possible. It is worth the extra few pennies per liter.
hi only got to stand till cold. tryed all this, even useing dummy tank...cheers bone
 

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Discussion Starter · #7 ·
OP reports that bike only has to sit for a day or even just a few hours and then it is hard to start.

I don't recall the KZ650's of that era being cold blooded, so based on the these two facts, I think we can rule out OEM cold bloodedness.

Check for vacuum leaks, including the choke. Check the air screws. Check the float levels and clean the carbs. Make sure the air filter is clean. Also have you checked valve clearance? Did anyone forget a rag in the intake somewhere?
What is the engine compression like?

Also suspect is the 3rd party electronic ignition conversion.
hi..checked all air screws. paid 400 quid for carb overhall and set up.new air filter, no rags left in. ignition seems ok. got good sparks...cheers bone
 

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The first thing to understand about your KZ is that it does not have a choke it has an enricher circuit. When the slide is in the idle position and the engine cranked with the enricher plunger raised air passes under the raised plunger, high vacuum ahead of the slide pulls air thru a small hole in the airbox side of the carb. The air bypass the venturi and exits ahead of the slide. At the same time it picks up fuel not thru the pilot or main jet but thru that brass tube you see when removing the float bowl. The system works but needs to be treated somewhat differently than a true choke, Also it must be adjusted properly.. Make sure all the plungers are free and rise high enough to open the ports. The engine must be healthy and in good tune so that the slides are not abnormally high to produce a useful idle. If the slides are raised for any reason, either poor tune or rider cracks the throttle, the vac. ahead of the slide will be reduced and the air will pass thru the venturi instead of the enricher circuit. Time and again I have seen riders inadvertently open the throttle as they attempt a cold start. With the hand gripping the throttle it is easy to slightly rotate it when the thumb is lowered to the starter button. Also some mechanics don't fully understand the system and may not have checked the enricher circuit. It is a dedicated function and if not operating properly will generally not affect the warm performance of the engine.
 

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I understand that, sometimes the enricher knob/lever is even labeled choke. However it is doing the operator a disservice by not properly labeling and explaining its function. A true choke will not be defeated by slightly opening the throttle where an enricher will be. So many no starts, so much wear and tear on starter and battery because the operator does not understand the difference. The manufactures take the easy way out but I believe most here are looking for answers and are bright enough to understand. More than once I had a customer complain their brand new less than one thousand miles on the clock motorcycle would not start cold. So when they came to pick the bike up after a full service .and the engine was cold I would say lets go it and give it a try. Sure enough crank, crank, crank and no start. I would tell them take your hand completely off the throttle and just poke a finger at the starter button....instant start.
 
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