Hey guys,

I've run Mobil1 75-90 in my gear box and FD for a while now in my 1985 k100rs.

I wanted to move up to Royal Purple, and I've heard a lot of people say its a solid choice, but my reservation is because on the back of the RP bottle, it says, "not for use in wet clutch vehicles such as most motorcycles." I'm guessing this is because, on the front, the RP bottle advertises that it contains Friction Modifier Additives.

My room mate is a car mechanic, and he advises that I skip anything with friction modifiers on a motorcycle.

Does anyone have any thoughts or knowledge on this topic? is RP going to cause clutch wear, change performance, etc?

Thanks all!


royal purple 75w90 in question:
http://www.canadiantire.ca/en/pdp/royal-purple-75w-90-synthetic-gear-oil-0280241p.html#.VNA9jp3F_y0

Unlike nearly every other motorcycle, the K bikes have dry clutches, and thus are not affected by friction reducing additives. 

In my bikes I just throw in a couple tablespoons of 1.5 micron molybdenum disulfide powder to reduce friction and make the shifting a lot easier.  I've heard that's what they use in the transmissions in the NASCAR racers.  It is also used to reduce friction and heat buildup in helicopter gearboxes.

ah!! interesting! I guess I'm good to go then. Thanks, PointSevenFive.

While I'm at it, does changing the oil in the FD and transmission tanks benefit from having the bike warmed up first, or does it not make much of a difference? The bike has been sitting for a long time, so I'm hesitant to run it without changing oil first

Transmission and final drive oil Take a while to heat up, and even then are still going to be rather thick.  With the bike sitting overnight most of the oil will drain off the parts and settle in the bottom.  Don't run anything, just open the drain plugs and let them drain for a while until the dripping slows way down.

If there is any metal in the drained oil, I would refill with some cheap stuff, run the bike a few miles and drain again before putting in the good stuff.

My bikes have benefited from the use of good quality synthetic oil at all points in the drive train, particularly in the gearbox of one. Much smoother shifting compared to whatever was in it when I got it.

Having whichever oil is being changed warm is a benefit in taking less time to drain as much as it will. There will always be some left inside, whether coating surfaces or in small pools where it can't drain from. If you don't warm it up, just leave it draining longer.

Just saw Point Seven Five's latest post. Words of wisdom.

Bill

Just my .02 on Royal Purple synthetic gear oil -  

In the past I'd settled on Mobil 1 75-140 with moly additive from Guard Dog which worked fine.  However, the owner of Guard Dog recently retired so he is now out of business and I was left in a quandry to find a new source for moly additive.

In poking around I discovered that Royal Purple comes with moly already in it so I decided to give it a try in a 93 K1100LT I recently brought back to life.

Having just completed a 2,000+ mile ride on the K1100LT I must say that the Royal Purple 75-140 synthetic gear oil works incredibly well in making a K transmission about as smooth as it can be.  It's what I'll be using in all of my Ks from now on.

The downside is that it's flippin' expensive stuff.  I found the best deal was to buy it from Pep Boys via Fleabay.

I've got at least 4000 miles with Royal Purple 75-90 (probably more) and I think it has improved the shifting a fair bit.  I will put it in again on the next change and will go to the 75-140.