For the Shovelhead Riders

[CCI]

Follow-up on my question from a while back -- 20w-50 mixed with straight 60 is holding up real well so far and the bike is much easier to kick start in colder weather. I'm sticking with it. Once we get up into the triple digit temps I'll see how it handles the heat and check back in. But at 90 mph at 60F it sounded fine and was still pulling hard.

For those interested, this particular engine does not like 20w-50, the motor sounds terrible on it in hot weather and for some reason it shears down really fast. This is a stock displacement 74 that will break the back tire loose on dry pavement in first gear without touching the clutch, running compression check says 215 in one cylinder and 235 in the other. I can see how it might be a little hard on oil -- and everything else.

For comparison, a stock everything 74 with an original factory cam and 8:1 pistons is doing fine on Mobil1 20w-50.

Thanks to all who helped.

 

[BrocLuno]

Roller bearing bottom ends are a lot different on oil than plain bearings ...

You might try some Castrol 10W-60 RS sometime. All synthetic and pretty shear stable in my experience. But my 74 incher is not as potent as yours

 

[Linctex]

I still have my '79 FXEF (80") and I was wondering if I had an oddball. (9.4:1 comp)

I have never checked for shearing... but do you guys fight oil temps?

On straight 50 I can keep it 200-210, but when I tried 20W-50 ... 230 was the norm.

Conversely, my 1988 Evo 80" Softail never gets above 200 on a hot day.

Same exact "horsehoe" oil tank on both bikes (Cookin' the poor battery!)

 

[CCI]

That's true -- very different requirements for the roller bearing bottom end. Mostly what I've seen over the years is if oil is getting to them, and the motor isn't being abused, they are fine. It doesn't take much. I have built bottom ends that have far exceeded what conventional wisdom says an old HD will do. The big trouble happens at the cam and tappet rollers and the relatively large piston to cylinder wall clearance.

I will check out the Castrol --thanks, I did not even know that existed.

 

[CCI]

I still have my '79 FXEF (80") and I was wondering if I had an oddball. (9.4:1 comp)

Good for you! That was one of my favorites. That compression ratio is higher than stock, but there is nothing wrong with it, they tend to run great on decent gasoline, especially with high-overlap cams.

I thought about calculating the actual compression ratio on this one but I did not take the time to cc the heads. Maybe next time I have it apart. I'm expecting that it's right up there.

I have never checked for shearing... but do you guys fight oil temps?

I don't worry about it, as soon as the mechanical sound of the motor changes at highway speeds in the three digit temps I change the oil. With some oils it was about a thousand miles,so I quit using them, some would go twice that. In cold weather I will let the oil go quite a while, in hot weather I change it often. I don't know who makes RevTech oil but I'm seeing good results with it, it holds up to heat even better than Delo SAE50 HDEO.

Back in the mid 1980s HD published some guidance on oil and temperature, if I recall correctly, every 20 degree increase over 200 degrees meant a dramatic decrease in oil life, and temps in the 230 degree range were really hard on the oil, and consequently the motor. I tried various oil coolers over the years and never really saw that much difference under extreme temp/severe service conditions. What I concluded was if the oil temp was routinely exceeding 220, just change it more often.


Conversely, my 1988 Evo 80" Softail never gets above 200 on a hot day.


That matches my experience as well. The Evos run cooler and last longer. I'm thinking about an Evo, I think they have been out long enough that I can finally trust them.

 

[endeavor to persevere]

Red Line makes a 20W60 motorcycle oil that is really good.

 

[CCI]

Looks good, I think I will give that a try. At $16 a quart I should probably fix a few oil leaks first.