Question about GS750 motor

[pasteurized]

A buddy of mine just picked up a '79 GS750 and we were messing around with it a little today. The motor was a little stuck but some penetrant spray and a few minutes later, it was turning over just like my 750. Except it will not turn 360 degrees. I can turn it roughly 180 degrees with it in neutral or with the clutch on, but no further. I would think that it should turn over indefinately. What would make it stop in either direction? We have not tried to start it with a starter yet, I want to make sure the motor is ok first. We tried to turn it over via the 19mm nut under the timing cover. What gives?

[SqDancerLynn1]

I would put some marvel mystery oil in the cyl & let it soak over night
If that doesn't help I would check & make sure that a valve is not stuck open

[bwringer]

It does sound more like one or more valves is stuck open for some reason (bent stem? rust?), or maybe the cam chain skipped with all the horsing around.

I'd pull the valve cover and see if the cam chain is moving and the cams are timed correctly. Stuck valves, if any, should then become evident.

Hopefully if it's mistimed it didn't happen while the engine is running.

[pasteurized]

I guess this is where my lack of knowledge of engine internals shows. Why would a stuck valve keep the rotating mass from turning? The carbs, exhaust, and plugs are out of the motor (and carbs and exhaust have been off for roughly a year, as it has been sitting outside in the weather, that sort of bugs me). Emptied the oil to move the bike and it was half oil, half water. Can't be good. All of the plug holes have been filled with deep creep (that's what we have) and it has been sprayed liberally in the exhaust holes, and the "intake manifold" as well. I don't want to deal with rebuilding this motor. Let's say tomorrow comes and it is still giving me problems. What are my options for action? I haven't tried really cranking the motor hard via the crank bolt under the timing cover, should I give it hell in hopes it breaks something free?

[Buffalo Breath]

engine

Bad news the motor is junk, find a new one

[pasteurized]

Buffalo Breath, care to elaborate??

[humhead]

If you found water in the crankcase/transmission, the damage due to rust & corrosion HAS to be considerable. Gears, bearings, shafts etc. will have rusted beyond any hope of repair.
If you have the time & tools, take it apart & see for yourself. Be warned - It won't be a pretty sight!

Terry

[Buffalo Breath]

junk

water and oil seperate so what was in the crank case has rusted every thing not covered by oil, not good, outside for a year with no carbs and exhaust equals water in the cylinders witch is more than likely the cause of the crankcase having water in it, rusted cylinders witch wont hold compression due to pitting and other damage to the cylinders, if a valve is causing the lack of full rotation its because the piston is hitting the valve, or, there is so much rust in the cylinders that it is hitting a large rust spot and jamming up, look in the plug holes with a flash lite, if all rusty well junker, my guess is that the crank is more than likely junk, but if the cylinders look good pull the v/c and check as suggested by others but also pull the pan and check the insde of the bottom end DONT spend any money till you know that its got, good luck you will need it.

[earlfor]

With the bike sitting outside for a year without plugs, carbs or exhaust and the engine half full of water, I think its pretty safe to say its a goner.
There will be too much internal rust damage to consider tearing down and repairing. Its far cheaper and easier to buy another engine on ebay.

Earl

[quote="pasteurized"]
The carbs, exhaust, and plugs are out of the motor (and carbs and exhaust have been off for roughly a year, as it has been sitting outside in the weather, that sort of bugs me). Emptied the oil to move the bike and it was half oil, half water.

[pasteurized]

Thanks for the input guys. Will see what happens tomorrow, but to be honest this would be a great opportunity to tear the engine down and get a hands on of some of the internals.

[Buffalo Breath]

engine

Thats the right attitude, you can learn a bunch from a tear down

[pasteurized]

Just an update, nothing changed overnight. I think a rebuild is in order, or at least a teardown and see what exactly happened.

Thanks for the input, all.

[robinjo]

Are you gonna show us?

*Marks topic for replies*

[pasteurized]

Heh yea I will, but it may take a little time before I get to it.

[JayH]

I know what pasteurized is going to be working on this winter.