Oil Weights

Any oil that comes in contact with the clutch can not have any non friction additives. That is the best reason to use ATF. If in a 4 stroke that does not use different oil for the clutch, transmission, and top end you must use oil with no non friction additives.

Long time heavy equipment/truck mechanic here. Keep in mind that one of the main requirements for tractor transmission fluid and ATF is that they must flow through some really small passages/orifices to operate the shift functions on those transmissions. If the fluid won't flow properly through the valves, particularly when cold, then the transmission won't shift or engage clutches properly. That is the reason those oils are such light viscosities.

In equipment with wet brakes in drive axles, where the fluid doesn't operate a shift function, you'll almost always find spec'd something like an 80/90 standard gear oil. If its just a gear box or drive axle without a clutch pack such as wet brakes, you'll almost always find a heavier oil like a SAE 140. If it's an extreme load or temperature application, heavy synthetic is often recommended, but without clutches in my experience.

My observation is that bike transmissions are most like the drive axle with wet brakes so all my Husky's from 1970 CR400 with it's little bitty clutch up to the 1983 CR500 get 80/90. I fiddle with the clutch until it works properly and have always managed to get good results, within reason, they're old machines after all. Just my opinion, your results may vary.

I liked reading your post however yes my results vary. For John Deere tractors in the utility class it seems the problem with the cold is the pump does not work for a while, perhaps cavitation. I stayed away from the power reverser transmission so can't comment on the passages/orifices from above. It does not make any difference whether it has the power reverser or the dry clutch for the oil called for. It has the steering pump and wet brakes not sure if they are a pack like husky clutches and may or may not be hydraulic brakes off the same system.

What is the difference between the 80-90 hypoid oil that stinks and stuff that seems much thinner and does not stink?

At any rate I have a five gallon pail of the Deere product around and know using the bel ray stuff from new the gears still wear out. Thinking about it these Husky gears are the only ones I can remember wearing out as opposed to damage from bearing pieces in other things.

ive never worn out a gearbox?

"ive never worn out a gearbox? "

For the primary kick models that I class as having been worn out the small gear on the back of the clutch does what I call wears out. There was a change in those parts somewhere around 1984-1985 and while the gear on the back of the clutch probably was a bit better it seems that no hardening treatment was done to the bore of the intermediate gear and those do what I class as wear out. A third gear on I believe to be the input shaft is pretty hard to find that is really worth re-installing we could debate if worn out applies there. That is for the widest available transmission. But on the other hand with a good oil and proper changes there are most likely going to be a few bearing pockets that ought to be sleeved and perhaps some other magnesium attachment point issues by that time.

admittedly, my bikes only ever did 2 seasons or so so i never tested their durability. the worst thing ever happened was the big end on my 84 kdx 250 failed cos mr mcHanic skimmed the head to get some more go? (just needed to set the timing a tad advanced to get the same result )

Would the Spectro 'Clutch Saver' 10W30 be OK for older Huskys? I can get locally.

Hi all. Interesting thread. Help me out with one thing please: when there is talk about ATF-F oil, do you mean to use it in older 4-strokes as well?
Correct me if I am wrong, but that cannot be used to lubricate the drive train and piston at the same time, can it?

No ATF in a 4 stroke, just in a 2 stroke gear box.

the atf -f is a special atf for early ford auto's..borg warner 35's.. its a slightly heavier oil than std ATF's