Originally Posted By: Clevy
Originally Posted By: alarmguy
While I am at it ... ha ha ...
While people think protecting gears are important, simply look at Amsoils own motor oil test that show how GOOD almost EVERY MOTOR OIL they test does protecting gears, page 15 of Study of Motorcycle oils.
Those same people forget about all the bearings in their transmissions and motor oil protects them best, its important for oil to easily flow in and around the bearings so they run cooler. Instead of thick gear lube not flowing fast enough the bearings cook or super heat, most likely no harm but they do come out of transmissions in motorcycles a deep dark color vs people who use motor oil ... again, will it harm it ?, most maybe likely not, but your bearings will be protected better with motor oil, Amsoil knows this, Mobile 1 knows this and your motor company knows this. Its why they recommend motor oil.
One more thing, some use a 80/140 type gear lube because it makes the transmission nice and quiet and shifting so pleasant. Even though the motor company recommended a 20/50 motor oil for a reason.
Yeah, nice and quiet is great but if it was best for the transmissions long life the motor company could easily use it and have nice quiet transmissions.
Same analogy, we could also put 60 or 70 weight oil in the engine, have super quiet engines, great idea but you'll be overheating those bearings as that oil slowly circulates around them. ... hmmm ...
I keep seeing the word flow here which puzzles me considering the tranny sits in an oil bath and really doesn't flow at all. And if that's the case a thicker more sticky gear oil would be a better choice considering how it operates.
And oil companies tow the manufacturers line. Fir example Amsoil's site just parrots what harley says. Redline might be different.
I don't have a sporty. I've hit a big twin and therefore 3 holes and my tranny performs far better using gear oil than 20w-50. I use rotella in my primary and in the engine this past season and I'm using rotella over the Amsoil I've got dirtying in a case.
Ultimately you can't go wrong following the manufacturers recommendations however if you've got a mind that works consider the mechanical operation of the machine and decide if it's optimal in your application.
Engine oil has and additive package that does many things,none of which are shared by a transmission and when you consider a motorcycle transmission is more consistent with a differential and gears meshing it's very possible that a gear oil is more optimal and the additive package better suited.
I'm just suggesting that one thinks for himself and considers the whole package and makes a choice based on that.
I agree with Clevy 100%. I know this has been beat to death in this post, but there seems to be real misunderstanding on how Harley motors lubricate themselves. Modern Harley's as well as older Harley's rely on a low pressure high volume dry sump systems for their motors. That's because of the type of bearing used in them. Mostly Roller type over babett type.They don't need high pressure to do their job, so pretty much any weight oil will give sufficient lubrication.5-7 pounds at idle is fine, and 35-40 at 2500 rpms or higher gives enough flow to satisfy it's bearings. Has anyone wondered with so many motorcycle specific oils on the market, ones that were designed with Harley's usage in mind, why Harley would recommend a Diesel oil be used if Harley's oil wasn't available?. Last time I checked Harley doesn't make a diesel motor, so why wouldn't they recommend Amsoil, or Redline, or Valvoline, or Mobil 1 V-twin oil? Just that one point, makes me wonder what they are trying to pull recommending what they do. On to transmissions.There is no oil pump in either Big Twins trans, or in Sportster primary/transmissions. They rely on a splash system for lubrication. It can't get more simple then that. Harley still recommends their SYN III oil or their primay oil for transmission oil use. Their primary oil is plain 50 wt oil with very little additives, and SYN III really seems like the wrong stuff to put in a Harley transmission. It's almost scary to hear a brand new bike whine or bang into gear, mostly because of what the ever knowing factory feels is the "proper" lubricant. Hot motor oil's film is super thin when it gets hot, so being sheared out of grade is a real possibility in your transmission. Gear oil is made for use in transmissions and rear ends where it's job is to lubricate gears and bearings.The exact same things found in a Harley transmission. It's weight is approximately the same as the oil Harley calls for, but doesn't have ingredients that are not needed, necessary, or helpful. Like whats needed in a diesel motor doesn't do squat for a Harley motor. Just like you wouldn't use gear oil in your motor, why would you use motor oil in a transmission?. There are better lube choices available outside the dealers showroom. I've never heard anyone say they like the winning noise their transmission makes, or the bang their bike makes when going into first gear adds to riding experience. When a simple brand of oil change can cure both.,,,
