My wife and I took a 50 mi ride today, then I parked the bike so I could change the oil. I let it sit for an hour to let it cool down a little. I changed the oil and checked the transmission oil level. When I pulled the dipstick out there was foam on it. I took my flashlight and look in the filler hole and could see foam on top of the oil everywhere I could see.

I don't remember seeing this before. I usually use dino gear oil. When I changed transmission oil the last time I used Royal Purple 75w140. Is this a problem? Has anybody seen this before?

 

Not seen it myself or heard of it so I'll be watching for more responses. Almost sounds like the oil was low and the gears caused a cavitating affect with the oil.

 

This is just my opinion but I am well read and been doing a lot of reading and checking. As far as transmission is concerned, it has some petty small needle type roller bearings in the main drive gear were the main shaft input shaft comes back thru. It also some some pretty fast spinning gears. Spinning a lot faster then 140 weight was ever intended for. You may have two problem here. One is the oil is too thick to provide any flushing of the small needle bearings and is also so thick that once aerated it very slow to let the bubbles out and from what I understand at least in a pressurized system is bad. Transmission is not pressurized but it does have a flinger on the end of the clutch pushrod on the right side of the transmission. I has yet to figure what it does. This is the vent area for the primary and I think it may actual prevent oil from merging thru to primary more then for help in lubrication.. Doubt most people ride a Harley hard or long enough to cause problems even if you used Wesson oil in there but IN MY OPINION 140 is too thick. I did some checking and Harley Formula + is a tad thicker then 75-90 GL5 SYN. However transmission does not call for GL5 lube.
As a final thought in a pressurized system such as the motor aerated oil would reduce the amount of oil thru the system. In the transmission this would not be the case since if anything the oil would just be higher in the case. However I guess it could cause a cavitation effect as the bubbles burst as they rolled under the rollers and cause an erosion effect. There are a few (at least 2 HA) smarter people on the Forum who could answer this. I been studying bearing wear and will see what I can find out about this.

 

OK thanks for the replies. I'll wait till tomorrow and see if anything else pops up here. If not, I'm probably gonna go back to the dino. I don't remember the viscosity but I have a quart in the shop.

 

Did not realize your 75-140 was SYN. Its probably thinner they what I think of as 75-140. I have had 3 Toyota 4x4's with 5 speeds since 1983. The first one I had when I change the oil in the transmission I change it to 85-90 dyno oil back then and you could hardly shift it. I guess that was around 86 or so. I ask around and a Castrol sales rep got in touch with me and arranged to give me a couple of gallons of what he called synthetic 75-90. Said he could take no money for it. At the time he said it was very special and costly to produce. He pumped it out of a 55 gal barrel he had into a couple plastic jugs for me. Said it would be on the market shortly. Looked thru a couple of bearing manuals on wear and do not see a much mention of cavitation wear on roller bearing, just on shell bearings like in most car cranks and rods. They say its 75wt., it should be OK. Oil guys say you should be concerned if it GL5 but I have yet to have someone say there is yellow metal in a Harley transmission. I have never taken one apart myself.
I been testing oils in my transmission for about a few months now checking out some of the things you read on the Forum about transmission clunk. Now using Harley +. In fact just put in in last Thursday. Since its what Harley recommends I will get back here after my next ride and let you know how much foam I see with a light and maybe count the bubbles or something like that on the dip stick to make it real scientific consumer report type.. Maybe Harley wants it to foam so you can see it on the stick. I've change mine 4 times in the last two months and its a pain to see new oil on the stick. Tried 15-50 dyno oil, 75-90 syn. syn 3 and now Formula + .

 

Finally quit raining. Ten mile run. Checked transmission. Same as your's. Plenty of foam. Guess it makes sense with gears spinning in open oil.