TOPIC:

A simple way to check for either vapor lock or a bad/broken wire in the resistor would be to run the bike with no air cleaner. Once it has warmed up and won't restart, squirt some fuel into the air box as close to the carb inlets as you can get it. If it fires at all, the resistor wire is good, and now you're looking at a fuel problem, like vapor lock.

Starter fluid might be easier to squirt into the air box than fuel.

I’m not an expert by any stretch of the imagination, more a hit it with a big hammer kind of guy. However I had a similar problem with mine starting from hot, and this is what worked for me. I cranked mine over so much I flattened the battery, pushed it over to the other side of the road, let it coast down the hill, clicked it into second and it started right up with no problems.
I reckoned the coils were faulty, but without the additional load of the starter motor they were still able to produce enough current. I renewed the coils and have had no further problems. So try bump starting it the next time it won’t go. If it starts right up then I would suspect the coils. Hope this helps.

Nothing more fascinating than trouble shooting a problem like this. Can't wait for the "A Hah" moment Touringguy.
you might want to go for a ride with that test sparkplug in your pocket and then when it acts up pull off spark plug wire #1 and test for spark with the test plug with a gap of 3/8". then check sparkplug wire #2 and then sparkplug wire #3. That will check all 3 coils.
Another dumb thought came to mind. I was looking for replacement spark plug caps and found NGK made them in about 3 different resistances 1K ohm, 3K ohm and I think 10 K ohms for giggles I went and tested the caps I had on the ends of the original wires and found 5K ohm caps, but at one point I wondered about the possibility of a straight cap without resistance and did some researching and found it was possible to remove the resistor in the cap and replace it with a solid wire preferably copper. Anyway to get to the point if you look down the end of the cap at the piece that fits over the sparkplug the brass piece has a slot in it for a screwdriver. I found a couple of them in the original Kawasaki spark plug caps loose by a couple of turns and for giggles I took them apart and found a pencil resistor.

When it's hot and won't start, starting fluid won't start it, either. I've tried that. but after it has cooled down a while, starting fluid will work. Because the coils have recovered enough to produce a weak spark, but a spark strong enough to ignite a highly-flammable fuel? If I let it cool down all the way, and it will fire back up without starting fluid.

I've just about decided to replace the coils with a Dyna or Accel kit this summer. So I'll be asking for advice on that process -- which brand is best, how they mount, etc.

I've also noticed that my gas mileage has gone down the tubes -- more evidence of poor ignition.

touringguy wrote: When it's hot and won't start, starting fluid won't start it, either. I've tried that. but after it has cooled down a while, starting fluid will work. Because the coils have recovered enough to produce a weak spark, but a spark strong enough to ignite a highly-flammable fuel? If I let it cool down all the way, and it will fire back up without starting fluid.

I've just about decided to replace the coils with a Dyna or Accel kit this summer. So I'll be asking for advice on that process -- which brand is best, how they mount, etc.

I've also noticed that my gas mileage has gone down the tubes -- more evidence of poor ignition.

First, coils don't "recover" I've never seen a coil go bad because of heat and then ok when it cools. It's obviously a heat related problem and I suspect fuel related BUT I wouldn't rule out compression related now that you tell me your fuel consumption is in the toilet. I'd also suspect compression if you've been playing with ether. My personal preference for "starting fuel is a spray bottle like the one produced by WD40 and put gasoline in it, then just spray the carbs lightly. If it won't go with gasoline, then why go any further?

If you want to go and change the coils for a piece of mind that's not a bad idea anyway. The AW-82 coil option is also a good one. Z1 Enterprises sells a three pack kit with solid core wires for around $98 U.S. They OHM out at 2.6 ohms and can be used without the ballast resistor. There are a few members on site who've done this one mod and are happy. That's the way I'm going. Like the price and a chance to eliminate the ballast resistor, plus the fact that they are physically the same size as the Kawasaki coils and mount in the same place with no modifications to brackets etc. . TrikeBuilder was writing up a tutorial on the pros and cons of the "modified ignition systems" but hasn't finished it yet. He brought up an interesting point about the repercussions of not having the ballast resistor in place and I respect his opinion very much. I hope he chimes in here with his thoughts again on running without the ballast resistor.

Anyway, I'd really like to know your compression readings hot and cold and while I ask that question, I'd also like to reinforce my belief in the leak down test being even more important than a compression test. Leakdown testing will show ALL of the defects in piston ring sealing, faulty intake and exhaust valves, head gaskets, cracked heads or cylinders and "tell" you where the mechanical problem is.
Sitting on the sidelines now waiting for your next post.
Kawboy

Hi,

I have had issues with hot starting on my -79 and -82 bikes. One idea that has been bounced around and has logic to it is:
Our carbs feed fuel due to the vacuum created by the pistons.
If the vacuum is not created, the fuel will not flow.
Therefore, having the idle adjustment screw set too high prevents the creation of sufficient vacuum and therefore starting.
When you start the bike cold, you use choke = add fuel to the system. When starting hot, you do not use choke = no start.
As written in the earlier comments, bump starting a bike which refuses to start hot works every time.

I have adjusted the idle screw to minimum to gain maximum vacuum.

I believe the hot starting problems are due to the insufficient vacuum, battery voltage going low due to starting and causing weaker spark.


Lauri