Okay, I give, where is the crancase vent on a 1972 GT380??

[wavehog33]

I have a newly rebuilt 72 GT380 that has crankcase oil running from an area just behind and above the front sprocket. Looking at a 73 case I have, I see a passage in the top case, between the countershaft bearing seats, towards the rear of the engine. Is this really the crankcase vent?? Certain I have not overfilled, so why is oil running from that hole after running the engine for 10 min and bike on the kickstand? And, whats the solution?????

[Vintageman]

The vent is rear of the oil pump and towards the right side of bike on case top.

http://www.ebay.com/itm/72-SUZUKI-GT380 ... xl&vxp=mtr" onclick="window.open(this.href);return false;

just behind and above the front sprocket.

Not sure from this verbiage the exact location. But, is oil coming from sprocket seal, neutral switch O'ring, clutch rod seal, gear selector or kick starter seal?

[wavehog33]

The vent is rear of the oil pump and towards the right side of bike on case top.

http://www.ebay.com/itm/72-SUZUKI-GT380 ... xl&vxp=mtr" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

just behind and above the front sprocket.

Not sure from this verbiage the exact location. But, is oil coming from sprocket seal, neutral switch O'ring, clutch rod seal, gear selector or kick starter seal?

Some more research. Yes, I checked my vent behind the oil pump and I can draw vacuum from the vent through to the oil fill cap. So, the case is venting fine. I have an oil leak from an area just behind the area where is case bolts are visible that go through from the top case to the bottom case. These bolts are visible on each side of the front sprocket. The leak is from behind the bolt to the left of the sprocket, It is not the countershaft seal, the clutch seal, shift seal, neutral switch or the rubber kicker plug. I notice that on the 73 cases I have as a spare set there is a hole, like a casting hole, between the counter bearings in the top case. My 73 case has this hole which is the same my 72 case is leaking from? However, I looked at cases from a 75 today and that casting hole is factory plugged? IS this a known problem with the 380? Cant imagine this hole is designed to be open as the oil that is flowing to oil the counter bearings will leak out and run all over behind the sprocket cover area? As mine is doing???

[wavehog33]

This picture shows this hole. This is the top case upside down. The oil passage area between where the countershaft bearings would sit. The picture shows there is hole in the rear section, this hole comes out near the front sprocket between the case bolts. It leaks oil down the left side behind the sprocket cover. SHOULD THIS BE A HOLE OR SHOULD IT BE PLUGGED???


This picture shows a case from a 75 GT380, same area and the hole is clearly plugged? Why is this one plugged and the other pic open?? Did Suzuki plug the from the factory and a known problem of the plug backing out???

[Alan H]

'Favourite' place in to leak in that area, is the neutral/gear indicator switch.
There's a thin O ring that perishes, or twists if you've replaced the switch.

[wavehog33]

'Favourite' place in to leak in that area, is the neutral/gear indicator switch.
There's a thin O ring that perishes, or twists if you've replaced the switch.

Understand that....but if you read the post its no where near that area.....can you explain though how one case in the pic has a hole near the counter bearings and the other pic that area is plugged>>>

[jabcb]

Suzuki modified the GT380 crankcase to increase the oil capacity. This included a relocated breather + some other mods.
See Service Bulletin GT-10: http://www.ozebook.com/compendium/techb ... 007-13.pdf

[wavehog33]

Suzuki modified the GT380 crankcase to increase the oil capacity. This included a relocated breather + some other mods.
See Service Bulletin GT-10: http://www.ozebook.com/compendium/techb ... 007-13.pdf

There is the answer.. .thank you!!

[Vintageman]

Are you saying that hole actually takes a turn and make its way out near the rear sprocket . Dang you would think a lot of dirt would have entered the engine through that open orifice That is always a sandy/dirty area

So when they raised oil level, oil it came out of there if not plugged. Not sure if the low oil level was the original issue or dirt getting into that hole then into gears.

Maybe I still don't understand unless you took a side picture? looking at ebay cases at this time I can't see clear enough if an exit hole exist. And your pic the hole is not through unless it takes a 90 degree turn.

[wavehog33]

Are you saying that hole actually takes a turn and make its way out near the rear sprocket . Dang you would think a lot of dirt would have entered the engine through that open orifice That is always a sandy/dirty area

So when they raised oil level, oil it came out of there if not plugged. Not sure if the low oil level was the original issue or dirt getting into that hole then into gears.

Maybe I still don't understand unless you took a side picture? looking at ebay cases at this time I can't see clear enough if an exit hole exist. And your pic the hole is not through unless it takes a 90 degree turn.

Yes, the hole is the factory vent hole....stupid.idea for sure. It alows oil to run out near the front sprocket. The bulletin from 74 addressed this, and offered a solution.

[Vintageman]

This is a good point. Once you own a bike you should read all Bulletins and see what applies.