GS750 engine seize

[Guest]

Hi all.
I have a 1977 GS750b that has stood for around a year in the garage, when i started the engine it seemed ok but after a short while the throttle response appeared to be getting sluggish then there was a squeaking type of noise and the engine stopped. When i tried to kick the engine over it was solid. after a short wait and oil down the bores the kick start freed the engine off and it now turns over ok. My question is has anyone come across a similar thing or what and where should i start to look at?, does the engine have any common faults to check?. the oil filter is out and the oil appears ok but i am not sure where to go from here.
Many thanks in anticipation.

 

[Brendan W]

Is the oil pressure lamp working. Get the valve cover off and see if oil has been getting to the top.
Does the oil smell of fuel. Drop the oil looking for pieces of metal.
If you find any take the sump plate off looking for more or a possible blockage of the oil pump strainer.

 

[steve murdoch]

Any chance the "after a short while" was a 15 minute or so idle without a fan blowing on the motor?

 

[GregT]

Given that your motor should be a roller bearing lower end, I'd look at the head first.
Pull the cam cover and look at the cam bearings. You can pull the caps off one at a time without disturbing the cam or the timing.

 

[Guest]

Thanks i will start there

 

[Guest]

yes it was stood for maybe 15 mins idling

 

[Guest]

the oil light does go off, i will take the valve covers off and check, the oil doesn't smell of fuel but i will take the sump off and check the pump strainer

 

[Guest]

I have put a new battery on as the old one was no good and turned the engine over with the plugs out and the oil pressure light is staying on, does this suggest a pump failure or possibly a blockage somewhere?

 

[Brendan W]

I have put a new battery on as the old one was no good and turned the engine over with the plugs out and the oil pressure light is staying on, does this suggest a pump failure or possibly a blockage somewhere?

Take the wire, G/Y ?, off the pressure switch and ground it out to the case. That should put the lamp out.
The switch itself is fairly robust so I wouldn't go opening that just yet.
Cold cranking with the plugs in, mine will put the oil lamp off.
You may have a pump strainer blockage or a pump drive problem.
If the clutch was tightened down with the pump drive dogs not engaged.

 

[Rich82GS750TZ]

Owners Manual Verbatim
“With the ignition switch in the ON position but the engine not started, the oil pressure indicator light should be lit. As soon as the engine is started the light should go out.”
That’s from an ‘82, but pretty sure yours would be the same.

 

[Redman]

Take the wire, G/Y ?, off the pressure switch and ground it out to the case. That should put the lamp out.
..................

No.

If the 750 is like all the other GSs that I know (80 & 82, 650G 850G 1100GK): Pulling the wire off the swtich should make the light go off. Grounding the wire to, well, ground should make the light come on.
Note: It is THE wire on the switch, correct? One conductor, One wire. THat wire is grounded out by the switch to make the light come on.

 

[Brendan W]

No.

If the 750 is like all the other GSs that I know (80 & 82, 650G 850G 1100GK): Pulling the wire off the swtich should make the light go off. Grounding the wire to, well, ground should make the light come on.
Note: It is THE wire on the switch, correct? One conductor, One wire. THat wire is grounded out by the switch to make the light come on.

Oooops!
Sometimes the wrong sense comes out.
Anyway the central idea is check switch and lamp operation first before assuming something and launching into a tear down with a dicky wire laughing it's socks off at you.

 

[Guest]

thanks i will check that

 

[Guest]

Thanks, the light is staying on unfortunately

 

[Redman]

Thanks, the light is staying on unfortunately

Meaning;the light stays on when pull connector off the oil pressure switch?
If so, Well, then there is a problem in the wiring or in the instrument cluster that is grounding out the circuit to keep the light on. WHich says nothing about the original problem of bike stalling out and seemingly seized engine.


If the light stays on with engine running , but will go off if pull the connector, THen can suspect either the oil pressure switch or is no oil pressure. Some one beside me will need to address the situation if is no oil pressure.

 

[londonboards]

But what was the screech?

Did something seize up?

You are going to need to check those cam bearings for sure but don't discount the possibility that it was the clutch suddenly loosening up, or the starter clutch having a fit.

Without stripping down the whole motor, it's going to be difficult to know. But for your own peace of mind, you need to try and find the cause of that noise. Maybe it was overheating, but I have not heard of that before, even running a motor for 15 minutes without moving.

Perhaps others have had the experience?

 

[Nessism]

15 minutes idling with no airflow is BAD. A fan is needed, blowing on the engine, if you have to leave the bike idling that long.


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