GT380 - Dumb Gearbox Oil Questions...

[eithr]

I feel pretty stupid asking this, but I can't find anything definitive online or in my manual.

1976 Suzuki GT380.

First, I've noticed some fluid leaking, which I'm assuming is oil from the transmission (which I'm assuming is different oil than that used in the engine). So, I'm nervous that the gearbox oil is low. Here's my dumb question:

How do I add oil to the gearbox?

On the left side of the engine, in what I'm assuming is the gearbox case, there's a rubber cap that I can screw off. When off, looking into that opening, I cannot see any oil. How do I check oil level in the gearbox? Will it cause any significant problems if I put too much oil in the gearbox?

This probably sounds pretty stupid, but to be fair this is my first bike and I'm still trying to figure stuff out. Any recommendations on gearbox oil? Would you recommend draining the current oil and putting in all new oil? If so, where is the drain point? Also, what might cause the gearbox leak?

Additional info...

As far as I know, the oil in the gearbox is the same stuff that the previous owner had in there. I acquired the bike about a year ago and being a newb wanting to log miles rather than wrench, I had a shop get the bike up to roadworthy condition. I had assumed that they would have changed the fluids, but the last time I talked to them they mentioned that they hadn't done anything with the oil in the gearbox.

I'm kinda itching to change the oil in gearbox anyway, because it's a bitch to get the bike into neutral when stopped at lights. The clutch should be fine (the shop adjusted it, as it was dragging significantly when first acquired). So, I'm thinking it's the oil. I've heard that trying a different oil might help with getting the bike into neutral at stops - does that make sense? What kind of oil would you recommend given this situation?

Thanks for any help.

[Scorch]

I feel pretty stupid asking this, but I can't find anything definitive online or in my manual.

1976 Suzuki GT380.

First, I've noticed some fluid leaking, which I'm assuming is oil from the transmission (which I'm assuming is different oil than that used in the engine). So, I'm nervous that the gearbox oil is low. Here's my dumb question:

How do I add oil to the gearbox?

On the left side of the engine, in what I'm assuming is the gearbox case, there's a rubber cap that I can screw off. When off, looking into that opening, I cannot see any oil. How do I check oil level in the gearbox? Will it cause any significant problems if I put too much oil in the gearbox?

This probably sounds pretty stupid, but to be fair this is my first bike and I'm still trying to figure stuff out. Any recommendations on gearbox oil? Would you recommend draining the current oil and putting in all new oil? If so, where is the drain point? Also, what might cause the gearbox leak?

Additional info...

As far as I know, the oil in the gearbox is the same stuff that the previous owner had in there. I acquired the bike about a year ago and being a newb wanting to log miles rather than wrench, I had a shop get the bike up to roadworthy condition. I had assumed that they would have changed the fluids, but the last time I talked to them they mentioned that they hadn't done anything with the oil in the gearbox.

I'm kinda itching to change the oil in gearbox anyway, because it's a bitch to get the bike into neutral when stopped at lights. The clutch should be fine (the shop adjusted it, as it was dragging significantly when first acquired). So, I'm thinking it's the oil. I've heard that trying a different oil might help with getting the bike into neutral at stops - does that make sense? What kind of oil would you recommend given this situation?

Thanks for any help.

Welcome to the forum!

I have a '75 GT380, and it has 1500cc stamped onto the clutch cover.

What I suggest is drain the old gearbox oil from the plug on the bottom, it inside the right pipe and center pipe under the bike. Replace the plug and then measure 1500cc of 10-40w motor oil slowly into the plug you mentioned.

As for leaks, you have to clean the bottom of the bike with engine degreaser and then just try to find them. Likely to be a leaking clutch cover.

Hope that helps, post some pics

[eithr]

Sweet. Thanks a bunch. As simple as this process may sound, I'm new to this stuff and just don't want to do something stupid with this cool old bike.

I found an old service manual on Dan's Motorcycle Repair site that recommended 20W/40 oil, so I ran out this morning to acquire some. Should that be fine? I don't know much about oil weight. Any reason to use one versus the other?

Thanks for the pic and simple explanation; seriously, I appreciate it.

[Scorch]

Yeah, as far as I know, either will work fine. It pays to be cautious, I ask a lot of questions here myself.

[jaybob]

Click the tranny into nuetral right before you come to a complete stop. It will make life a lot easier

[Buffalo-guy]

Also, Make sure that the oil you use is rated for motorcycles!! Quite important. Bike oil has friction modifiers in it for wet clutch compatibility, and additives to protect your harsh gearbox environment that it has to live in. Automotive oil has neither of these capabilities. Your bike will love you for it. Cheers.
Fred

[eithr]

Oil changed! And, the bike is operating noticably better - shifts easier into gear and into neutral. Even finding that I'm able to get the bike into neutral at stops now... still not as reliable as popping it into neutral when coasting up to a light, but I'm tickled.

The fluid that drained from the gearbox was very thin and very gray. I put Castrol 20/40 back in, and yes it was rated for bikes.

NEW QUESTION: When I drained the old oil from the bike, I noticed there wasn't a washer accompanying the drain plug bolt. Should there be a washer? If so, any chance anyone knows the size of that washer? Not positive, but I'm thinking that missing washer might be a reason for the oil I find in drips below the bike.

[Buffalo-guy]

There should be a washer!! The factory washer was just a standard sparkplug seal, same size as the plugs in your bike, 14 mm ID. Most auto outlets should have something for you, be it fiber, aluminum, or just another sparkplug affair, but get one for sure. Cheers.
Fred

[eithr]

Any chance there's a technique, aside from turning the bike upside down, that'll allow me to pull that plug off, so that I can slip the washer between the plug bolt and the engine bottom without dumping out all the oil?

Am I better off just leaving it as is until the next time I need to change the oil? My manual is recommending changing the gearbox oil every year. That seems rather vague. How often do you recommend changing that oil?

[Scorch]

I would leave it until next oil change, if it is not leaking.

[eithr]

I think I located the gearbox related oil leak. It seems to be coming from the foot shift lever, where it connects to the side of the engine. Oil is building up around the point of connection; when the bike is set on the side stand that oil very very slowly weeps. Should there be a gasket or oil seal of some kind there? I'm guessing that if there is, I'm missing that seal. Treasure hunting begins again.

So, this is the left side of the bike. I noticed something else, mildly upsetting. There's a small bit missing from the bottom of the engine - it's a small triangle of material missing from just behind the bottom rear bolt hole on the generator cover. Being a newb and not completely understanding what's going on here, I pulled the covers off to confirm that nothing was leaking from that hole. It appears to only prevent me from bolting the cover on all the way, as I can pass a bolt thru the cover, but there isn't anything behind it to screw the bolt into. Should I be concerned? Or is this not a big deal?

Also, any chance anyone knows where to get those thick rubber gaskets? The generator cover gasket is ill fitting; it appears the PO didn't fit it in properly, so it's all twisted awkwardly.

[eithr]

Oh. To install that oil seal, will I need to do a lot of engine disassembly? Winter projects galore this year.

[TLRam1]

Oil seal can be replaced from the outside, remove cover and shifter.