1976 R60/6 High Speed Cut Outs...

Fellow Airheads,

My trusty R60/6 has "high speed cut outs"... (whatever qualifies for high speed for an R60/6 here is what happens:

I am about 50 miles into my ride. Engine is warm, cool morning temperatures, (high sixties to mid seventies) at abpout 65 to 70 miles the engine starts "cutting out" first a bit, then more. I switch to reserve (both petcocks) problem remains... I slow down to about 55 to max. 60mph. Cutting out stops... i am pulling over to the next gas station and fill up. 3.8gallons. So I know it was not empty... (the R60/6 has the large tank). After topping up the gas tank, no more cut outs back to 65-70mph cruising speed. What do you think my problem is?

My R60/6 has:
Stock ignition with points
Single plugged
Stock Bing Carbs
Stock 600cc

is it time for an electiric upgrade? Your thougths, ideas, comments, of what the cause is are much appreciated.

Thank you.

Picture is from this morning ride and the bike in question.

I'd check to be sure the floats are set right. You should have the slide carbs. I think the amount of fuel in the bowl should be around an inch after you turn off the petcock and lower the bowl.

Next time it starts cutting out, carefully crack open the gas cap. If the problem goes away, could be the tank is not venting through the cap.

20774 said:

I'd check to be sure the floats are set right. You should have the slide carbs. I think the amount of fuel in the bowl should be around an inch after you turn off the petcock and lower the bowl.

Next time it starts cutting out, carefully crack open the gas cap. If the problem goes away, could be the tank is not venting through the cap.

Click to expand...

Wil do, thank you Kurt. I'll also have a look at the venting hole in the gas cap. So you don't think it's electrical... ?! BTW no red charging light is on. I appreciate your quick feedback. Thank you.

I would have thought that an electrical problem would show up most any time, not just after driving for a while. You slow down to 55-60 and the problem goes away. At slower speeds, the demands for gas also goes down. I'm thinking your floats are either set for low fuel in the bowl or the gas tank doesn't vent properly. You might be on the margins or a fuel issue. You're OK early in the ride, but as the time goes by and speeds pick up, the amount of fuel being supplied begins to drop below what the engine requires.

But it could be electrical, too!

20774 said:

I would have thought that an electrical problem would show up most any time, not just after driving for a while. You slow down to 55-60 and the problem goes away. At slower speeds, the demands for gas also goes down. I'm thinking your floats are either set for low fuel in the bowl or the gas tank doesn't vent properly. You might be on the margins or a fuel issue. You're OK early in the ride, but as the time goes by and speeds pick up, the amount of fuel being supplied begins to drop below what the engine requires.

But it could be electrical, too!

Click to expand...

Thank you again! I'll check both, fuel level in the carb bowles and the venting of the gas tank. Ugh, I dread electrical problems...

points condenser

I have seen a bad points condenser cause such a problem. St.

Gas cap vent

I also had a bad gas cap vent. For some reason, the planets align when I screw the cap down too tight on my newly painted tank. This blocks the vent and down the road, the bike acts like it runs out of gas. Inspection of the cap shows the vent to be clear. I just don't tighten the cap as tight as I did.

What have you found out so far? St.

I was having similar problems with my 75/5 I checked everything and nothing worked. On the second time I removed the tank and cleaned it out. I just changed the strainers on well I am here lets change them. The old ones are discolored but look good other wise. Problem went away. one would think that a test of flow with the bike sitting in the driveway and checking fuel flow would catch this it did not. I used to have an issue over 80 every time the bike was low on fuel (less than 1/2 tank) Toaster so this is not much.
I routinely go to 100 now until it need so go to reserve.
Gator

Sounds like a problem with a spark plug wire.

/Guenther

My mistake

I am sorry, I did not take time to read the question properly.

If I had, I would never have brought up the condenser.

Very much sounds like a problem with either a blocked vent, dirty screens or gas flow.

As I said, I have a venting problem in one of my airheads.

Loosen the cap and it runs fine.

Tighten the cap and it may run fine for five minutes, an hour, a day, or a week but, it will screw up. Once the cap is loose, it runs fine all the time.

Mind you the vent itself is clear however, in my case, a new layer of paint causes just the right condition to block the vent causing the problem.

It took a few rides and stops along the side of the road to figure it out. St.

Well thank you everyone for the replies. Cleaned air venting hole, checked floats, (ok) and tightend a loose right carburetor. The cut out went away.

A couple weeks ago I completed sucsessfully a SS 1,000. Not a single cut out. Ride report can be found here.

Slow and Fast
Congratulations on finishing your Iron butt 1000 and giving us a great write up to boot!
That's a sweet ride you got there,
I'm glad you got it sorted out and did your dream ride on it
Whahooo
Ride safe

I would have bet on Guenther’s Plug Wires suggestion.

An overlooked cause of ”carb problems” that can be heat related.

Glad you found the source of your problem.

Charlie

Thank you for the note nickrides, I appreciate it.

As far about resolving the cut out problem... I am not really sure. I did replaced spark plug wires and cap in 2016. I cleanded the tank before heading out on a 1000 miler. looked for airleaks where the intake tubes/carbs are and as mentioned already. tightend the right carb.

I do believe the cooler than anticipated temperatures helped on the SS 1000. I have a tendency to overthink it but that there was not a single cut out over a 21 hour plus and 1,000 miles plus ride lets my mind be at ease - for now - if anything developes I keep you posted.

Thank you all once more.