tired of engine dying - please help!

1981 KZ305 CSR

carbs have been cleaned and serviced by kawasaki. ignition timing has been checked with a timing light. plugs are new and properly gapped. the bike runs great until it gets fully warmed up, then there's an occasional miss and suddenly the engine dies. after cooling for a few minutes, it starts right up and runs strong until it gets hot again, then it's gone again. i thought it might be a dwell problem, which could cause the coils to overheat, so i rechecked the points, but they seem to be gapped just right. checked both coils with a multimeter, and they both meet the specs in the Clymer manual. any ideas anyone? could the coils be dying anyway?

Thanks!

It almost sounds like vapor lock. Will it do this standing in your driveway or are you running it hard and hot?

See if it stays running with the gas cap popped open. If it does then take off the cap and clean the vent. The vent needs to be open in order for the carb to get gas flow.

If it only happens after running a while and getting the engine hot, then it may be as simple as checking and adjusting the valves.

It may also be a funky coil, but the first two are easier to check and fix.

It may be your gas cap not venting. Next time it does it open the cap and see if you get any sucking noise or how fast it will start back up. How old is the fuel filter? Carry a spare spark plug with you, when it dies hook the plug onto a wire and crank the engine to see if you get a spark. It doesn't seem like both coils would die at the same time but stranger things have happened. Check the double plug connector that the coil + wires plug into, make sure the connections are clean and tight.
The condensors could cause it too, but like the coils it doesn't seem that they would both short out at the same time.
Do you lose everything ei: lights and all or just the ignition?
Ride safe.

Well Kent you beat me to it,,, :laugh:

Post edited by: The Milkman, at: 2007/06/19 23:17

hmmm. vapor lock. i'll check the gas cap. thanks.

the fuel filter is good. it's transparent, and i can see fuel passing through it.

the lights stay on when the engine dies. all i lose is the engine.

strangely, although there are 2 coils, there is only 1 condenser. i'll give it a check.

thanks again!

Acutally, it's hard to tell from the parts picture at buykawasaki.com but the condenser looks like is actually 2 joined to one bracket but butted end to end. On the 650 they were mounted side by side on one bracket.
Ride safe.

Check the points out closely, that the wires or the springs are not grounding against the plate, follow the wires up and make sure they arnt rubbed, melted through. A broken or loose points wire will cause the symtoms you related. The kill switch has srews inside that may have loosened.

Have the valve clearances been checked? If they are real close, the bike may start but the valves clearances will close up when warmer. I would replace the gas filter even though it looks OK and check to ensure the arrow on the filter points in the direction of gas flow. I would also try opening the gas cap when the bike stops or starts to stop to ensure that there isn't a vacuum being set up in the tank due to lack of venting.

Ok. Fuel filter is good, and in the right direction.

It's not vapor lock - tried running with gas cap open and it still died. I figured that would be the case, since with the gas cap closed I can rev the engine and keep it alive - there must be adequate fuel. Figured I'd check the gas cap thing anyway though.

Checked the points and wiring. Insulation is not worn, and nothing is grounding improperly.

The condenser is, in fact, two condensers mounted end-to-end, as suggested by The Milkman. They both check ok, per the tests given in Clymer. I even tried cooling them with compressed air as the engine started to act up, but it didn't help.

Have not had time to check the valves yet, but I'm getting to the point where that's the only choice left.

The problem definitely seems to be heat related. The exterior of the cylinder head gets to about 400 F before the engine starts idling slower and slower and then jsut dies. I'm used to water cooled bikes with temperature gauges, so I have no idea what the head temp should be. Is it possible that it's just overheating the engine? Any idea what temp I should be seeing for an engine that's running well?

what about the petcock, I think there is a screen in the tsnk it may be full of crap and not getting fuel all of the time, just a thought