Transmission (please esplain me)

So I drained the transmission fluid from my jawa, refilled with 4oz of Dexron III, tightend everything up and took it for a ride around the block. It idles perfectly, and runs at a slow speed well. When I try to accelerate it to half or full throttle, the bike 'bucks', like it's try to grab and pull me faster, but something is stopping it. If I ride it for say five minutes, it will also start to buck at slower speed. It never actually 'bogs', as in it dosent feel like it wants to stall, it just sort of dosent want to pull it's weight (or mine).

When I get back to my garage, the top of the transmission is coated with ATF oil where it has apparently leaked from a hole in the transmisson fill plug. In the bolt that acts as the fill plug there is a hole in the center of the slot across the top of the bolt.

My questions are

a) what is this hole for

b) is tranny fluid supposed to leak from it?

c) if not, what is causing it to leak from that hole.

d) does this sound like a tranny problem, clutch problem or just another "take teh carb apart and clean it again" scenario.

The jawa does not have an air filter, I had the petcock apart and cleaned, I have installed a new fuel line and fuel filter, and I've cleaned the carb very well (at the same time I added the fuel filter) I have not had teh clutch cover off yet so I'm not sure what is going on in there but I do here some metalic pinging coming from in side when the cluth first starts to grab and also I think I hear it after it bucks and tries to catch again.

Any ideas?

Re: Transmission (please esplain me)

Donald Wilson /

I have the same problem with a Sachs tranny, but the wee hole is on the side.

Sounds to me like it's a general Trans issue we should know how to deal with, but don't.

Re: Transmission (please esplain me)

I am not a Jawa expert, however the hole you mention is probably a vent hole so the air can expand out when it warms up without blowing seals. It probably should not leak much, if any, unless something is missing (say a small filter inside etc?). As long as it is not a serious leak, I would not worry a whole lot about it. Again I'm not familiar with the clutch. It may be slipping when engaged. This can be caused by worn plates, oil or grease on it, or weak springs. Guessing here but I hope it helps.



Re: Transmission (please esplain me)

Ok, I understand that it would need to breathe but it did leak quite a bit, enough to make a mess on the top of the tranny cover.

I guess I'll try to get the clutch cover off (have to buy a strap wrench) and have a look. It does feel like it's slipping underload but I've seen other threads where it came back to the carb. I'll try running it with the choke on to see if it'sa fuel problem (just thought of that)

I also notice that when it runs a little rough on the stand the drive chain seems to bounce around quite a bit even though it is fairly tight, like there is some vibration coming from the sproket that turns to chain.

Oh, also, this bike was off the road for close to 15 years. I just got it running again over the last two months.

Re: Transmission (please esplain me)

Are Jawas supposed to use atf? Most mopeds use something like non detergent 10w40 I think. Perhaps the atf is causing slippage, and if it is a detergent oil it might foam, which would explain the oil coming out of the vent hole.

Re: Transmission (please esplain me)

You know, it did look a little 'foamy' now that you mention it.

My original owners manual for the JAWA says to use 'ATF'. but it does not state what kind. I put Dexron III in it. Can I try draining it and putting in 10w 40 with out causing any issues? I dont know enough about it to know whether mixing or adding in a differnet kind of oil would screw anything up.

Re: Transmission (please esplain me)

People always say Type F non-detergent for some reason.

My Allstate is suppose to take 30wt motor oil, but I put straight Amsoil synthetic 2-stroke oil in it, and it's NEVER performed better.

I know someone with a QT50, that said when he put tranny fluid in it, it got a whole lot hotter, and gave him problems. He put oil in it, and's never had the problem.


Re: Transmission (please esplain me)

You're not _overfilling_ it are you?

Re: Transmission (please esplain me)

the original jawa owners manual says 4oz (half a cup) and when I fill it with that much (after draining it) it fills up and dribbles just a little bit from the check screw hole. I cant see how I could be over filling it.

Re: Transmission (please esplain me)

I'm willingto try differentoils in there but do I run the risk of messing something up if they mix a little bit I.e. will teh left over dribbles of dexron III mix with the 30 weight synthetic motor oil and turn into goo?

Did you say you used two stroke motor oil? You mean the kind I mix with the gas? :confused:

Re: Transmission (please esplain me)

Yeah, I don't know how your transmission is.

In my manual it calls for 30 wt. Back then they didn't have much else.

It's a 50's model. I put synthetic Amsoil 2-stroke in there, because I know of a couple of people who run it in there motocross racing bikes.

I was told it wouldn't hurt it, and actually clean it up, and lubricate it better, even if it got low.

I've had it in 2 motors, and have noticed a strong difference in less drag.

I love it in there, and it works great for me.

~But yeah, the stuff ya mix with the gas, but this is high quality synthetic, which I also use in the gas mixture, and will NEVER go back to the old stuff. So many plusses.

The only way I could see it hurting it, is if there were something more wrong, and riding it made it worse. Maybe you got a bearing staring to go? I don't know, I've never had that happen.


Re: Transmission (please esplain me)

MAybe after 15 years, your clutch material is just bad.

The fact that you hear metal pinging pretty much tells your that it's not a carb issue.. unless you are running so lean that your engine is about to melt itself down.

Re: Transmission (please esplain me)

ᴛᴇʀʀʏ ᴅᴇᴀɴ /

On your Sachs, that hole is an over-flow hole. You over filled your transmission, so some fluid came out of the over-flow hole.

Re: Transmission (please esplain me)

Nah, the pinging is deffinetly coming from in side the clutch cover. I'll pull it off and have a look. If I get that off I can always pull the tranny cover off as well and see if there is any goo built up in there, etc...

Re: Transmission (please esplain me)

I had a pinging that came from my tranny once on my Targa LX.

It was because the clutch nut fell off, and the crank seal was shoving the clutch pack into the tranny cover every time the piston came down.

you might check for something like that.

Re: Transmission (please esplain me)

Took the clutch cover off. everything looks fine. spring is in place,the three little doo-hikeys look ok. the little grabber material is in place. no oil or grease in there.

it's weird, I guess what's actually happening is that when I give it half or full throttle it's just not getting enough power. I tried choking it while I was riding it (that is supposed to richen the mixture) but that did not help, made it worse in that the bike just did not want to accelerate at all.

And there was no tranny fluid leak this time. I tried loosening the chain just a little bit as well, it was pretty tight, but that did not help. Also checked to see that the rear wheel was not dragging on the brake.

Back to the carburetor? Maybe the float is low? Lets see, open the throttle and it wants to suck in more air and more fuel right? so, assuming it'sgetting enough air, then we're not getting enough fuel. Means flow is restricted or low float.

Am I on the right track?

Re: Transmission (please esplain me)

You may have a blown crankshaft seal. Ford type F fluid is often called for because it's compatible with more types of the older seal material than the Dextron lll. It may be able to run at low speed but when you get enough rpms up the vacuum the piston pulls may be sucking air from the transmission case or worse ATF. If the seal is real bad it could be allowing fuel/air mixture through into the transmission oil at idle. This would cause your foaming when you are not really running the transmission hard.Try doing a leakdown test on it to see if the seals are working properly.

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