QuestionMike,
I'll try to be as specific as I can but as I did not rebuild the motor myself, I may not know some things in absolute detail. Plus, I'm not a mechanic but I do understand a fair amount (enough to get me in trouble sometimes). I have rebuilt a '67 t120tt in the past but it did not go beyond replacing worn out parts with NOS or new components.
I have a '72 XLH in a local shop and when the motor needed rebuilding, it was decided to install an S&S stroker kit - seemed like a good idea at the time. Now, the motor has been through three tear-downs as the shop is trying to locate the cause of oil being returned to the oil tank in a frothy condition. They have a good deal of my money and I can't afford getting the bike in someone else's hands at this point.
The rebuild was brought on when the stock motor went haywire - the oil pump apparently let go and all kinds of things let go after that. Anyway, the first thing to get replaced on the rebuild was the oil pump. I have been repeatedly assured that the pump is "perfect" and some modification was made to that part of the pump which is vertical - the opening was widened to the measure specified by S&S. Again, I have been assured that this modification is correct and has been executed correctly. I have been shown the pump and compared it to a stock unit. Mine looks to have near perfect close tolerances. Again, I've been told that all aspects of the pump are mechanically correct and that air is not entering the oiling system from the body of the oil pump.
The foaming problem has stumped these guys and others (reputable engine builders among them)who have been asked including tech people at S&S.
The crankcase venting has been checked and presumably ruled out as a cause. The oil lines have all been replaced. The gaskets for the oil pump have been replaced twice also. The oil pump surfaces that are supposed to be flat and mated to each other are indeed flat. The bike doesn't leak oil after the engine has been run for short periods.
The foaming does not occur immediately but takes a minute or two to appear. I've been told that the top end is getting non-frothed oil but I'm not confident about that. I've also been told by a few mechanics that I should just get on the bike and ride it. I'm not convinced that the motor won't self destruct.
The current thinking by the guys that built the motor is that they will try to alter the timing of the oil pump opening.
The mechanics are at a loss and everyone they speak to has a different answer or no answer.
I don't know what oil they are running in the bike but I suspect that it is 60 weight - probably Golden Spectro but definitely a motorcycle-specific oil that comes in a black bottle with orange lettering. That's the only oil I've seen them stock but I don't know who makes it. It isn't HD-brand oil...that much I do know. I run racing Pennzoil in my Triumph, so I don't have a reason to buy oil from them.
I have heard that HD makes a synthetic oil that has special anti-frothing agents so I assume that some motors may have similar problems of course depending on configuration.
If you have any suggestions as to how to cure this or what they can look for to eliminate any potential causes, I would be more than happy to share any information with them. I'm not exactly furious with them not being able to fix this but they appear to need a little help.
Thank you for your time.
AnswerYour "frothing of the oil" is quit common with the old iron head motors. The frothing happens from the turning of the flywheels churning the oil as it passes.
Do not change the timing of the oil pump body. You will get exsesive oil in the bottom end. As long as the pump is timed correctly to the motor (that oil pump has to be timed) and you have good oil pressure, you are fine. Normally the frothing stops after riding the bike a few miles, once it heats up.
The oil they are using is fine, unless you live in a high heat area, 90 to 100 degreees daily, then I would go with a 70 weight. WHen it turns cold outside go to a 50 weight.
Good luck and happy riding
Mike
