Sae 20 Substitute

I just acquired a 1986 XC400 and would like to give it a good once over before I ride it regularly. In looking at the manual it recommends SAE20 for the crankcase oil, but it is proving a little hard to find. Is 5w-20 an acceptable substitute?

Use ATF type F, easy to find and the clutch and gears will love it..
1 of my favorite bikes the 86 400 XC, congrats on the bike.

Steve, you use F type in the manual trans?

Torco MTF-L

I do

I use a synthetic oil also, or Torco MTF-L like motomwo says above
MTF is a manual transmission fluid for a gearbox that is not directly affecting the crankcase, ie a 2 stroke

Torco light gear oil (now MTF-L) is what I've used since Malcolm Smith recommended it when I got my new 1976 Husky from his shop. Good stuff. Made for these transmissions and clutches.

What weight is standard?

this is almost worth a long discourse on "lubricity" vs "clutch grab"
so without going into how viscosities are determined, and yes it is interesting
lets look at how much grip you want and how much gear protection you are willing to trade
if you can't effectively use your clutch then the gearbox is pretty useless in the real application
so type "F" atf is mentioned, it has a "grippy" property and as such makes a light clutch grab well
light clutch??? yes the trade off for a clutch that won't wear out your forearm but will grab with modern power
so,,, the trick is to protect the gears, as they are expensive to replace, have a clutch that you can use and not get arm pump
I personally use all the modern science I can, I use synthetic MTF, the reason for using synthetic is the difference in time, how often do you change your gear oil

Thank you for the responses! I ordered some of the recommended Torco, but will definitely be keeping an eye on this thread to see where it leads...

I don't know that particular bike but I am having good results with UTTO 10w30 oil in my two stroke gearboxes, using it for years with good clutch and transmission feel, fewer debris on the drainplug magnet as well.

i never liked the atf type f in my swedes..too many shavings on the magnet, and type f is thinner than the average 20wt..
for years now ive been using rotella t6 diesel 5w40, which is a bit thicker but produces MUCH less material on the magnet and still shifts nicely. much better anti-wear additives in a diesel oil than atf, and much more resistant to shear. rotella t4 and t6 are both jaso ma rated.

atf is around 5-7 cSt@100 degrees,
20 weight oil is anywhere from 6-10 cSt@100 degrees

the published "weight" of an oil doesnt mean much, the centistroke rating is much more accurate, and is usually easily gotten from an oils website

thats because 10w30 is a stout oil, and fairly close to the original recommended weight.

"gear" oil that is sae 80w...is the same thickness as almost a sae 30w "engine oil"

a 75w gear oil that played nice with a wet clutch would be ideal and provide excellent gear and bearing wear. the torco mentioned above fits this perfectly

Seems odd that a 75W gear oil would be a proper substitute for 20 weight engine oil. The gear oil would surely be great for the gearbox, but I can’t believe that the clutch would behave the same. There must be a reason that Husqvarna originally specified such a light viscosity oil.

At least the gear oil wouldn’t have any friction reducing additives like most modern automotive motor oils do. I’m inclined to try using a good motorcycle JASO MA rated 10W30 as that will be closest to what was originally specified. 5W20 oils would be closer in viscosity to straight weight 20, but none of those would be JASO MA.

Yes 75wt gear oil is the proper substitute for 20 wt motor oil. I have been using Torco MTF-L 75wt in all my manual clutch Huskys. No clutch drag or slipping.

Marty

https://www.belray.com/bel-ray-engine-oil-bel-ray-gear-oil-differences-explained/

For what it is worth, I have been using the Torco MTF-L (75wt) in my 86 XC 400 for about 2 years, per recommendations on here and have had no issues.

Thanks. I’ll give it a try.