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Okay, so I recently started working on a 77 kz650 four cylinder. I pulled it from a salvage yard and skated by with only paying 50 bucks. I had a new(er) set of carbs installed, new points and condenser, and starter and selinoid replaced. I recently cleaned the gas tank and had the clutch plate adjusted and everything timed. Now that I have layed some history out there, here's the problem. The bike rides great until it gets hot. About 15 minutes into the ride, the engine starts missing, the power level drops and the bike just seems to want to die. At first I thought the fuel line may be to narrow and replaced it, but sure enough, rode it last night and almost didn't make it home. I was hoping that someone could help me out. The coils are original and I had to splice some plug wires into the factory ones to make it work. I was hoping for some guidance (Bear in mind I am a nube to the whole mechanical aspect of a motorcycle) I hope ya'll can help me out.

ADC

I had a problem with my bike missing when it got warm. Turned out to be the coils. I found my problem by pulling the spark plug caps off when the bike was missing after a ride. It turned out to be only running on #2 and #3 at idle. When the bike was cold, it would run on all 4.
Good Luck

Thanks! I will check it out...any idea where to get new coils for cheap is that is the problem?

Another heat-related problem is valve adjustments. When they get hot, the valves no longer seal. You should check the clearances anyway, before burning valves.

I checked the valve clearance and they seem to be tighter that they are supposed to be, and I'm not sure if that could be a problem or not. Do you have any other thoughts?

Both suggestions so far on coils and valve clearance are good. How exactly did you check the valve clearance? When you say "they seem to be tighter than they are supposed to be" I kinda get a feeling you didn't measure them with a feeler gauge....that's ok I use to adjust my Hardley Ableson valves by feel...but Kaw's need more finess than that.

Check out this file in the KZ Rider filebase. It is a chart about valve adjustments for a 650.

KZ650 Valvelash

After you check the measurements if any are too tight then you need to loosen it up. This is done by replacing shims. Check all the valves against the chart and see which shim you need for each valve, and write it down. Then carefully unscrew the cam cap bolts, roll the cam out of the way, (don't remove it or jump the chain on the cam) and lift up the buckets. You may need a magnet to get the bucket out. You'll see a shim on top of the valve, or it may be stuck to the bucket. It has a number on it indicating the shim size. Check all the shims and see if you can swap them between valves to get the proper clearance. If you come up short then usually the service guys at a Kaw dealer will swap the shims for free, if they are cool about it. Otherwise it may cost 5-10 bucks unless someone here has extras for you. (I don't, sorry)

That's the simple way, I left stuff out because you should read and follow the manual first. (And I couldn't remember what they were )

The coils can be measured with an volt/ohm meter. Specs are in the manual. If you need coils there is always ebay, or you can buy new Dyna/Accel coils.

Post edited by: OKC_Kent, at: 2007/08/28 16:10

Thanks for all the advice. I did measure the valves with a metric feeler gauge. All but one of the valves fell within approx. .05 mm of the recommended values, which is why I was curious. I attempted to check the coils output, but my abilities with an ohm meter are somewhat lacking. The coils definitly are putting out, whether it is sufficient is of concern...