ATF In The H-D Primary

[BigCahuna]

I wouldn't use gear oil in a Sportster's primary. First, Harley doesn't recommend it. And second while it would work in a trans, it's too heavy for the clutch pack.I would bet you would have a hard time shifting and it would bang pretty going into first. 20/50 wt or 15/40 wt oil will work for alot less then expensive synthetic oils.,,

 

[RedCellRacing]

What is interesting is that once SYN3 came out, it was recommended for the Primary/Trans on the sporty (20w-50) yet at least on my 09, they have gone back to recommending Formula+. I was under the impression that Formula+ was a 75w-90 gear lube.

With regard to it being heavy, based on the viscosity of a few oils that I pulled, it looks like 20w-50 motor oil is about the same viscosity as 75w-90. Comparing AMSOIL 20w-50 (MCV) and 75w-90 (SVG) the 20w-50 is actually heavier.

SAE 20W-50 Synthetic Motorcycle Oil (MCV)
Kinematic Viscosity @ 100°C, cSt (ASTM D-445) 20.56
Kinematic Viscosity @ 40°C, cSt (ASTM D-445) 152.0
Viscosity Index (ASTM D-2270) 161

SEVERE GEAR® 75W-90 (SVG)
Kinematic Viscosity @ 100°C, cSt (ASTM D-445)16.7
Kinematic Viscosity @ 40°C, cst (ASTM D-445)109.1
Viscosity Index (ASTM D-2270) 165

Kind of sucks with the Sporty that the primary and trans are stuck with the same oil supply.

 

[boraticus]

Originally Posted By: BigCahuna
I wouldn't use gear oil in a Sportster's primary. First, Harley doesn't recommend it. And second while it would work in a trans, it's too heavy for the clutch pack.I would bet you would have a hard time shifting and it would bang pretty going into first. 20/50 wt or 15/40 wt oil will work for alot less then expensive synthetic oils.,,



I run Belray GearSaver in the transmissions on my old Yamaha RDs with no problems at all. Clutch works just fine, bikes shift slicker than anything else I have. I've never ridden anything with a nicer shifting transmission than these old Yamahas. They had it figured out way back then!

 

[Zedhed]

Originally Posted By: boraticus
Originally Posted By: BigCahuna
I wouldn't use gear oil in a Sportster's primary. First, Harley doesn't recommend it. And second while it would work in a trans, it's too heavy for the clutch pack.I would bet you would have a hard time shifting and it would bang pretty going into first. 20/50 wt or 15/40 wt oil will work for alot less then expensive synthetic oils.,,



I run Belray GearSaver in the transmissions on my old Yamaha RDs with no problems at all. Clutch works just fine, bikes shift slicker than anything else I have. I've never ridden anything with a nicer shifting transmission than these old Yamahas. They had it figured out way back then!


+1 my RDs always shifted great, now crank seals? That was a different story......Not as bad as my Mach IIIs but still a problem area.

 

[boraticus]

"+1 my RDs always shifted great, now crank seals? That was a different story......Not as bad as my Mach IIIs but still a problem area."

The crank seal issues isn't as prevalent as many might think. All two stroke engines are subject to crank seal failure but in my experience, it relatively rare. Seals will fail. It's only a matter of time. However, how much time is reasonable?

My '76 RD400 had bad crank seals so I rebuilt the entire engine, bottom to top.

On the other hand, I have two excellent running 1974 RD350s with all original bottom ends. I hopped up one of them that's now making approx. 50 rear wheel horse power. That's up from stock 39 h.p. That engine will spin cleanly to 10000 rpm making power all the way.

The other engine is completely stock with factory spec compression and it's running great too.

What must be recognized though is that both those RD350 engines are very fresh for their age. I doubt that they had much more than a thousand miles on them. The bike's odometer readings were low and according to serial numbers, these were not the original engines.

The '76 RD400 was hacked over pretty badly when I got it. Whoever had owned it, spent a lot of time flogging it down dusty dirt roads. The frame and engine had super fine clay dust on and in every possible nook and cranny. It had hardened on like concrete. The inside of the air intake on the clean side as well as the carbs had a film of this same dust on it. My thinking is that the seals do not tolerate the engine ingesting too much abrasive dust.

The other engines were spotless.

Keep the intake air clean and the seals will last a good long time.

Sorry for hi-jacking the post.