Suzuki 2 Strokes

Fellow smoke-eaters, I'm stuck here and reaching out for diagnostic help. I'm starting work on a GT750L (1974) that was a barn rescue. ("Ran when parked.")

Motor is stuck. With the head off, the cylinders actually seem pretty good, and I with some considerable (but careful) force on #3 piston I got it to move but only to the bottom of the stroke, or thereabouts. Then it's stuck again. I pulled the clutch cover off to inspect whether that metal band could have broken and got chewed up, but it's fine.

Given that the pistons do move but are basically stuck, and the barrels appear free of rust, I'd like to make a list of all the possible causes for a stuck engine. I know it's not much to go on, but I'd welcome your thoughts. Thanks.

Could be any number of things including fuel or oil in the bottom end. You could remove the SRIS valves from the crankcases and see what drains out. You could also add a little WD40 or penetrating oil to the bores in case it's rust at the bottom of the bore.

It is most likely that the crank is rusty and the seals are shot, so it will probably need a rebuilt crank when you get that far down into it.

Okay, you're bracing me for a crank rebuild. I was hoping it was strictly top end.
I'll try to get the barrels off and let you know what I find.

I agree it sounds like rusted bearings, I had several engines that had cranks rusted fast, I believe from condensation build up in lower end, You may need a cylinder puller to get cylinders off.

We are speculating, hypothesizing, based on what we think you are describing. It's too late to do a leakdown test if the head is already off, but that's OK. Just keep going and see what you find.

Barrels can be a total PIA to remove, but sometimes you get lucky and they pop off without much pain. Other than that and the weight, they are pretty simple motors. No camshafts and valves and counterbalance shafts etc to worry about. Just take your time.