transmission oil type and how to check level.

[stampee]

Hi all: What type oil do you use for the transmission? The book says 20-40 which is not easily found. I put in 20-50 but I am not sure this is correct, it may be to thick.

My 2nd) problem which scares me. I have a 1974 t500 with the supposedly modified crank case. It has the 1400 sticker on the case still. ANYHOW last year I started sucking transmission oil from the case.
I changed the crank seals recently. it smoked bad at idle after first start. It idled maybe 20 minutes. I ran it today, it smoked at first then was fine with no smoke for about an 8 mile ride. THEN 5th gear started howling.
I looked in the transmission filler and I can see oil, but... how much is there? Without a dipstick this is a real problem.
I checked the oil level plug and oil does come out, but, I hear that is drilled at the 1200 CC level.
Is the 20-50 oil to thick? Did I suck the transmission low already? Are the crank seals I installed leaking still?
Sighh.. I am not a happy camper now. I cant believe a 20 minute idle would have sucked oil down that badly.
Last year with the bad crank seals it smoked horribly all the time, non-stop. and I never heard a gear whine, except the first time when I found out the hard way I was sucking transmission oil.
Any advice on oil types and how to ascertain how much oil is in the transmission would be appreciated.
needless to say I do NOT want to be splitting the crankcase again to change a 5th gear bearing.
Thank you
-Stampee

[ConnerVT]

The only way you can currently check your crankcase oil level is to drain the crankcase, and measure what comes out. You will want to do this with the engine (oil) warm, to get most of it out, and realize that there will still be a small amount left. Tilting/rocking the bike will help move some of the last small amount of oil out.

You are correct, that the "oil level screw" is used to measure the 1200cc level. You may wish to remove that first, before draining the oil. It will tell you if you have at least 1200cc in the crankcase.

Some folks have fabricated a dip stick to fit in the oil filler cap. But you need to have a known good 1400cc of oil in the crankcase first, to know where to mark it.

20W50 oil is OK (I'm not even sure if they had 20W50 in the 70's - All I remember is 10W40 and straight 30W). Personally, I use gear oil in my bike, but not going to wade into another oil thread. Plenty written here about oil, please search around the site.

The gear whine is not a good sign. The noise is not from a bearing, but from the gear itself, which I believe is NLA part. Smoking can be caused by a number of reasons - a bad inner seal is only one of them. A failed seal is either going to happen after a long period of usage, or fail quickly (incorrect installation/bad part). First thing is to determine you have the correct level of oil. Then see the bike's oil usage and smoking characteristics.

Good luck.

[Coyote]

You are correct, that the "oil level screw" is used to measure the 1200cc level.

Why not fill it till it dribbles out of the 1200cc screw, then add 200 more?

[Alan H]

Depends on what sort of measuring jug they use Coyote - they might have one the same as that one with no marks on of yours!?!?

Just drain it and put 1400ml of 20w50 in. It's still available if you look.

[Coyote]

20W50 isn't rare. The books recommend 20W40. That is only available in some select bike shops and waaaaaayyy over priced. I use readily available 10W40 in my 550's. 20W50 in my GS1000

[ConnerVT]

You are correct, that the "oil level screw" is used to measure the 1200cc level.

Why not fill it till it dribbles out of the 1200cc screw, then add 200 more?

You could do it this way, but it wouldn't be my preferred method. You will be making assumptions (is the screw level really 1200cc? How low was it originally? Did the cool oil I refilled it with make it through all of the crankcase before coming out of the screw hole?....)

Much better is to drain the case. Measure and inspect the oil removed. Refill with a known 1400cc. Observe (smoking/gear noise). Ride for a bit. Drain and measure (it can go back in the case, it is still very fresh oil).

By doing it in this manner, I would be much more confident in the data, to make a much better, educated decision.