Suzuki 2 Strokes

Have a 1972 GT380 project bike with a 1974 motor. Am thinking about finally working on it.

The entire two stroke oil tank leaked out while I’ve had it. The leak stopped now that the tank is empty.
It was a slow drip with the last drip shown on the crankcase bolt in front of where the SRIS tubes go though the crankcase.


I can see the drop, but where is it leaking from?
Do I need to pull the motor & check something inside + reseal the crankcase?

I have replacement oil lines — I’ll check the one-way valves before installing it.
Will also take the pump apart & make sure the plungers are working. (A new oil pump gasket is on its way from the UK.)

Also noticed the missing bolt that should be in front of the center SRIS connector.

Loose pipe from tank to pump. Don't ask why I know this.

Thanks for the info.

What is the path of oil from the leaky pipe to dripping off a bolt near the front of the motor?

Now that will be the interesting bit. On my 550 it was across the engine under the carbs and through the sris rubbers, but also across the swing arm where it fastens to the frame, then forwards under the engine. Don't expect the obvious. Clean it all then start looking.

Thanks again for the insight.

I had this type of leak on a T350. But that resulted in muck all over the place and the cause was rather obvious.

I didn’t think of this easy-to-fix problem. But consistent with your explanation, there also is a drop of oil on one of the SRIS lines. (See lower left in the pic.)

Don't expect it to be straightforward. If it was easy everyone would have a classic 2 stroke!

I would make very sure that the crankcase isn't full of oil. Hydro-lock would be ugly. Many bikes have drain holes to allow fuel or oil spills to drain out the bottom. Not sure about that model.



Lane

I was worried about that.
Before you mentioned a leaking tank-to-pump oil line, I was thinking that the center cylinder crankcase had filled up & it was leaking out because the case halves were not sealed correctly.

I kicked the bike over with the carbs & spark plugs removed. It seemed fine.

I removed the SRIS lines & quite bit of oil drained out of the one for center cylinder.

Suzuki eliminated the SRIS for the 1975 & later models.
So I replaced the crankcase SRIS connectors with the bolt+washer used on the later models.

The smallest vacuum line caps the auto parts store have are too big to seal off the cylinder SRIS connector.
Any suggestions for a reversible way to seal those off those ports?

Found an easy way to seal off the cylinder SRIS connector.

The SRIS lines are 2mm ID & 5mm OD. And 5mm is a little over 3/16”.
So I used a short section of SRIS line just enough to cover the connector.
Shortened a 3/16” auto vacuum cap a bit, and installed it over the SRIS line.

Leak saga resolved.

An oil line broke when I was undoing the union bolts. It snapped off at the union bolt connector nearest to the SRIS crankcase passage. Apparently the line was damaged & the leak went unnoticed because the oil went down the SRIS crankcase passage.

Had good spare oil lines & everything is back together. Only got a few drops of oil near the pump where I had made a bit of a mess.