Suzuki 2 Strokes

Hi, I'm a new member. I have a '73 GT250 and a '76 GT550, both restored. I've recently taken my GT550 out of storage and on starting the engine made a terrible clattering noise and locked up. After removing covers and manually turning shafts the engine freed up. I've removed the clutch, cleaned and replaced it and everything seems OK. The starter motor also runs freely. One thing I have noticed is unburnt oil in the exhaust. I'm just wondering if during storage 2 stroke oil has slowly drained from the oil tank through the pump and into the crank, and perhaps this was the cause of the engine locking up. I know excess 2 stroke oil in the crank is transferred up into the cylinders, but this will only apply to small amounts during normal running. My next step is to remove the oil pipes from the engine to see if oil will run through them without the engine and pump running. The engine was professionally restored 5 years ago and has run fine until this issue. Many thanks for your thoughts.

It sounds like it hydro locked. Oil seeped into the cylinder from the tank. In many cases this means you have bent a rod but hopefully you got lucky.

There a tests to check it.

Can you tell me what tests can be carried out?
Also, is there a way to remove excess oil from the crank without an engine strip?

You can remove the SRIS valves from the lower front of engine to drain crankcase, or remove the spark plugs and turn over, cover the engine with rags, this method makes a mess.
With oil lines full, hang them with check valves down.
I have 2 bikes that did the same, but now seem fine, if it only happens during storage I would just remove plugs before turning over next time out of storage to see if it happens again.

Hydro lock also occurs when petcock left in prime and needle valve leaks filling crank with fuel.
Never use compressed air to blow oil lines, It will damage check valves

this is what usually happens when it hydro locks. my mate's suzuki t200 invader crank before i rebuilt it
cheers, dd.
hydrolocked rod:

While hydro lock is a very serious condition, it is not a guarantee any damage has been done. My GT550 and GT185 suffered from oil hydro lock, and my GT250 had fuel hydro lock. None of them sustained any damage from it. In my opinion, the starting system isn't strong enough to do much internal damage, the damage is done when another cylinder fires. So if you caught it soon enough before another cylinder fired there is a good chance there isn't damage.

Thank you for your input. I've removed the SRIS tubes from the engine and also taken off the cylinder head. The pistons are all moving freely when the crank is turned manually. I'm assuming if the one of the rods had been bent this would not be possible? The engine only fired once when it locked up. Also, when rotating the engine, oil is squirting out of the middle cylinder crank SRIS inlet hole and I can hear the squishing of oil in the crank - see photo. There is no oil coming out of the left and right crank SRIS holes. Do I just keep rotating the engine until no more oil is coming out and assume this is sufficient to rebuild and start again. Thereafter, how do I stop this happening again? Many thanks.

You need to remove the SRIS check valves from the front of crankcase,not just the tubes, this will allow the oil to run out.
It only takes engine firing once to cause damage, if you have the head off it is not much more to remove cylinder to check rod.

Thanks Karl. I removed the SRIS tubes at the front as suggested (not easy with the frame in the way) and 1/4 litre/8.5 fluid ounces of oil came out. Do you know how much oil should be retained in the crank in normal conditions? Removing the barrels and checking the conrods is the next job. After resolving the current situation I will need new SRIS lines with working check valves to stop seepage occurring again, assuming they are still available, or do you know if there is an alternative solution?

Labradoodle wrote: ↑Mon Nov 13, 2023 11:27 am Do you know how much oil should be retained in the crank in normal condi

Basically none, just a coating on internal parts

Labradoodle wrote: ↑Mon Nov 13, 2023 11:27 am I will need new SRIS lines with working check valves to stop seepage occurring again

The SRIS check valves are not the same as the CCI system check valves. And the CCI check valves are not available from Suzuki, but some use Kawasaki valves, I can't help there. First I would hang your CCI lines check valve down and see if they leak.