Losing power and dying after 10 minutes

[BAT]

Mine tapers. It will run fine at all rpms, then start to cut out in the uppers, then the lower as well, but midrange is fine. Then it requires more and more throttle to maintain the rpms until it quickly tapers to dead.

I've taken the cap off, didn't notice a vacuum and it didn't change anything. The carbs have fuel when it dies.

Its strange thats its at both high and low rpms, but midrange was clean. Its been getting harder and harder to start and now idles better with choke, even after warming up. It ran like crap the last time I started it and took it for a short ride, right from the start. No power, bad throttle response, all cylinders were firing.

What about pickups?

[j20brett]

hmm. Back to fundamentals then.

has the valve clearance been checked? May be that the valves are heating up, growing and losing their seal (going zero clearance while hot)

Like the valve lash might be too tight you think?

[BAT]

It should just run poorly then, the whole engine shouldn't die. What are the chances that the valvetrain would tighten up in more than two cylinders?

[j20brett]

Mine never fully dies. It did that once and it took like 10 min t start it back up. Ever since its just cut out a cylinder randomly.

[reelrazor]

Like the valve lash might be too tight you think?

Be worth checking. It's just a little labor involved to rule it out.

[j20brett]

Another shot in the dark here. My stator cover gets hot, like really hot. Hot enough that it'll burn the piss outta you if you leave your finger on it more than half a second. Normal? Could the stator be getting hot and building up resistance and throwing the voltage off?

[haro504]

have you checked the air filter might not be it. but could have a nest or something in there and at wot it starts to starve for air then flood the engine while you have it apart couldent hurt to check

[j20brett]

No birds nest. i can run it WOT through every gear and im assuming when it hits a certain tamp, something goes crazy in the wiring.

[reelrazor]

Another shot in the dark here. My stator cover gets hot, like really hot. Hot enough that it'll burn the piss outta you if you leave your finger on it more than half a second. Normal? Could the stator be getting hot and building up resistance and throwing the voltage off?

yes, this is possible. Your best bet to narrow that down is to test the resistance thru the stator and pickup wires twice..once while cold, once while hot and see how much change the meter registers.

My experience is that the stator cover will normally get hot, but not so hot you can't touch it for a few seconds

[j20brett]

So test it where the wires come out if the stator im assuming? Or where they go into the VR? Which would be easiest? Ill get it done this weekend. What voltage is normal?

[reelrazor]

So test it where the wires come out if the stator im assuming? Or where they go into the VR? Which would be easiest? Ill get it done this weekend. What voltage is normal?

35-50VAC across all possible pairs of the white stator wires (while running at 3000rpm). I'd do it at the stator and pickup coil connectors above the left side of the engine. Voltage for the pickup wires not testable.

Do the resistance test as well-with engine off. Stator wires should show .31-.37ohms cold. Pickup coil wires should show 80-120 ohms cold. And, none of the stator wires (three white wires) should show continuity to ground (engine case), nor should the pickup coil wires.

[j20brett]

Excellent. You are the man!

[j20brett]

Ok so i apparently dont know what im looking for when it comes to the pickup coil wires, couldnt find them but im sure they were right there in front of me. Anyways the resistance through the 3 white stator wires were roughly .7 - .8 ohms. Didnt check AC voltage yet. Ground to frame i would assume?

[reelrazor]

Ok so i apparently dont know what im looking for when it comes to the pickup coil wires, couldnt find them but im sure they were right there in front of me. Anyways the resistance through the 3 white stator wires were roughly .7 - .8 ohms. Didnt check AC voltage yet. Ground to frame i would assume?

The pickup coil wires will be a separate two wire connector block coming from under the stator cover..right in the neighborhood of the stator output wires (the three white)...maybe some years they are all paired together in ONE connector block?

the pickup wires are white with a red trace and white with a black trace.

The stator resistance (from white to another white....NOT from white to ground) should be .31-.37 ohms. Check all three pairings.

To test stator voltage output you set the meter to AC and go from white to white as well (NOT white to ground)...3000rpm.

[j20brett]

the pickup wires are white with a red trace and white with a black trace.

The stator resistance (from white to another white....NOT from white to ground) should be .31-.37 ohms. Check all three pairings.

To test stator voltage output you set the meter to AC and go from white to white as well (NOT white to ground)...3000rpm.

For all three pairings measured wire to wire (cold), they ranged .7 - .8 ohms

Will test stator output tonight. Thanks! I did see that pairing color for the coil pickup next to the tank. Will pull the tank when i get a chance and check that later.