'86 700 stumbling and quitting

Very curious to learn if anyone has input for me : '86 700, purchased in '90 with 2300 miles and now with 196,000. Last summer the beast developed a problem where it would start to stumble - more throttle and/or choke would help, but only for another half mile or so and it would die. After many times I developed the technique of simply counting to sixty, then it would re-fire. And 98% of the time would be OK for the remainder of the ride (two or three times it quit a second time, and then was OK after that). Problem sure seems to be temperature related, but not as you might think : if ambient temp was 70, say, then no problem. Only have seen this problem when it is 60 or below. Seemed like some component would warm up to some specific temp and cause grief... But then why would the short sixty second rest almost always reset it ? Twice whilst riding in the rain at around fifty degrees it did NOT happen. Rode once with the gas tank cap popped but the beast quit anyhow. Spark unit is all the way by the tail light, so that seems to rule that out. I saw another post here for an 86 750 with somewhat-similar issue, and it seemed that replacing the fuel stop relay helped there. Without my service manual available this second, I am not sure what the fuel stop relay is - or does it simply refer to the fuel pump relay ? That I have replaced, along with the fuel pump. Fuel lines from tank to carbs as well. My next thought was to replace all four coils. Open to suggestions - thanks !

 

I would look at the pulsar coils (not the ignition coils) next. They are under the right crankcase cover bolted towards the front around the starter clutch housing, which has raised triggers. These are usually the temperature related culprits of ignition problems.

You can also jump the Fuel Cut Relay as a test too, but I don't think that is your problem. Fuel Cut Relay is a safety device that prevents the fuel pump from continuing to pump if the bike is not running or being cranked, but the ignition is still on (like in a crash). They are known to fail, but usually fail completely. I wire in parallel toggle switches on my bikes so I can prime the fuel system after winter storage or get home WHEN the relay fails.

 

in addition to capt 80's reply above, replace the main fuel filter, and if you're up for a carb r/r , get in and clean the small filters above the float needle seats. test fuel flow from pump output hose into a bucket (jump the pump relay).

next time it quits have a spare sparkplug handy so you can grab a wire from one of the rear cylinders and test for spark.

if the mileage you state is real time for a compression test. 196k is nearly a world record.

 

OK, folks, I do appreciate the input.
Capt 80s : I pawed-through my service manual and see zero mention of 'pulsar coils'. Other than ignition coils I only see mention of Cam Pulse Generator ('86 only) and the two Pulse Generators. Do you mean one of those two pieces ?
Squirrelman : Don't see how it could be the fuel filter (which I have replaced several times now) if the problem occurs and then goes away. Problem has got to be temperature-related, as it occurs around-about the same distance from home. I had the carbs rebuilt for my 750 VFR (8400 miles), and reinstalling them was brutal. Which has made me reluctant to take them off of the 700, but I am sure after all this time/mileage it would be a good idea. And, I will admit to being a bit torqued about the mileage comment : totally correct, zeke. Started with 2300 and now at 196,000. Been to CA and back. Ohio/Michigan a few times. Once down to Tennessee. Commute on it everyday once the snow is gone and until it returns; rain, wind, cold, whatever. Bring it.

 

Yes, thats what I'm talking about.

 

just as you say.......i had pulse generator coil failure on one of my '86s. started and ran fine until things heated up, then no spark. why you need to check for sparks as soon as it quits.

 

OK , great input. I will replace the cam pulse generator and the crank pulse generators and go from there. Thanks again.

 

I have never heard of the cam sensor going bad (you're talking about the one on the back of the front head?). Its the crank pulse generators that give problems.

 

big problem i think as the set of 2 crank pulsers may be NLA, and one may need to source from a bike breaker ?

i hope i'm wrong.