Shovelhead Shuts Down When Hot

[HogsRear]

Did you happen to check it to see if it was bad???????????? Or are you just going to assume it's bad??????

It tested ok not running but I wanted to switch to a sealed battery that fits in the oil bag a little better anyways so I will keep the old one as backup.

[TriNortchopz]

If your alternator and regulator are operating as intended, don't even need a battery with your points type ignition.

[Skjoll]

Are you still getting a spark on both cylinders after the motor shuts down? Is there fuel in the carb's bowl after the motor shuts down? I have yet to see any results from attempting to diagnose the problem.

[HogsRear]

Are you still getting a spark on both cylinders after the motor shuts down? Is there fuel in the carb's bowl after the motor shuts down? I have yet to see any results from attempting to diagnose the problem.

Yes and yes.

[Skjoll]

What you've described sounds so much like inadequate or zero valve clearance when cold so as the motor heats up and the valve gear tightens up, the valves are prevented from closing completely until they remain open far enough that you no longer have adequate compression for the air/fuel mix to ignite.

[farmall]

What Skjoll said. I'd readjust the tappets. It's common to get them too tight.

Loose is life, tight burns valves.

[JBinNC]

What you've described sounds so much like inadequate or zero valve clearance when cold so as the motor heats up and the valve gear tightens up, the valves are prevented from closing completely until they remain open far enough that you no longer have adequate compression for the air/fuel mix to ignite.

With shovels, the opposite happens. The cylinders grow (it's a tall motor) and the valve lash increases on solids.

Jim

[JBinNC]

What Skjoll said. I'd readjust the tappets. It's common to get them too tight.

Loose is life, tight burns valves.

+++^^^

Most people try to adjust the valves too tight in an attempt to make them quieter. I think that is an error.

Jim

[HogsRear]

+++^^^

Most people try to adjust the valves too tight in an attempt to make them quieter. I think that is an error.

Jim

Interesting, I guess this could be what's happening. I checked my pushrods when I changed the points a couple weeks ago and everything seemed fine (not loose, but still able to spin them in my fingers) but I will check again.

[Skjoll]

With shovels, the opposite happens. The cylinders grow (it's a tall motor) and the valve lash increases on solids.

Jim

Do you find this to be true with just shovelheads or have you known other HD motors to behave the same way?

[Sky]

A lot of good advice in this thread so far...
Are you certain your issue is heat related? Vibration is synonymous with Shovelheads

Double checking or even adding good ground(s) has not been mentioned yet.

Ignition switches can be finicky with heat and vibration.

Is your carb properly insulated?



With Shovels you've got
Iron cylinders
Aluminum cases, heads and rocker boxes
Steel cam, lifters, rockers and seats
Pushrods can be aluminum or steel
They all expand at different rates thermally...
The pushrod material can make a big difference as to how tight or loose the cold valve lash is set.

So, I like to "spin check" solids with the bike warm
Only way to know for sure

[Tattooo]

Do you find this to be true with just shovelheads or have you known other HD motors to behave the same way?

Yep...................

[47str8leg]

Sounds to me like a main breaker.

[Sky]

Main breaker wouldn't show a deterioration of performance.
Just a sudden lack of spark (and lights) till it resets.
But I have seen corrroded/damaged breakers. loose posts, lose bolts, bad crimps....

[47str8leg]

Main breaker wouldn't show a deterioration of performance.
Just a sudden lack of spark (and lights) till it resets.
But I have seen corrroded/damaged breakers. loose posts, lose bolts, bad crimps....

Have to disagree as I had the same exact symptoms on my full dresser about 15 years ago.lights blinking on and off , speedo going crazy , bike sputtering till it died. Wait 20 minutes, bike fired back up and go down the road fine for another 20-30 miles. Was down in Florida for bike week and wanted to ride down to the Keys. Bike started acting up so. I bailed on it. Lucky for me friends had a bus set up for bikes with tools . Kept looking at a whole bunch of shit like the O.P. . Thought. I had it figured out and tried riding it home ( N.Y. ). 30 miles later ( as had been happening all week )
I loaded it on the bus.
Got it back home and after chasing down wiring figuring it had to be a short . Flabbergasted I figured there was nothing else left to check I changed the main.
Bingo.