Gt750K resurrection - excessive smoke on right cylinder

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Salmanz8
Posts: 65
Joined: Tue Mar 16, 2021 4:39 am
Location: Edmonton AB Canada

Gt750K resurrection - excessive smoke on right cylinder

Post by Salmanz8 »

Hi guys.

My gt750k, i acquired a few months back, is now running.
Did loads of work. Frame, suspension etc and carbs.
Bike started easy, and starts easy everytime.

There was a but of weeping coolant around the head, but i didnt pay much attention to it, to deal with it later.

There is a bit of clutch noise, which goes away once the clutch is pulled in.

After finally putting the tank on, and having it go through the gears in my parking lot, there was excessive smoke from the right #3 cylinder.

After a day of idling, running, doing other work, i pulled the baffle from that pipe today and it certainly has water on it.
Inside the pipe, further confirms the presence of water.
Spark plug is wet, but cleaner than the other three ( steam cleaning ? )

I held the oil pump at full and there is certainly a difference of colour of smoke.

I am concluding so far that coolant is making its way into the cylinder.
So the question is what are the possible points of entry ?
I havnt taken the head off yet, in case there is any further testing to be done.

Bike doesnt over heat, i will be switching hoses as they are crunchy. Sometimes after a blip of throttle the revs sort of hang for a sec at 2k and then come down to idle. ( air leak around the head gasket )

First i thought it was burning gear oil, but i think it is coolant.

Anyone has had similar issue ?

Bike has unknown history, but seemingly it was serviced, but by a very incompetent mechanic, whi absolutely had no clue what he was doing.
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Alan H
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Joined: Fri Aug 05, 2011 6:38 am
Location: Wombwell, Republic of South Yorkshire

Re: Gt750K resurrection - excessive smoke on right cylinder

Post by Alan H »

Does the coolant level actually drop?
It's recommended to put some Barrs leak fix in when it's first filled after a strip.
Proof that four strokes are over complicated
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Salmanz8
Posts: 65
Joined: Tue Mar 16, 2021 4:39 am
Location: Edmonton AB Canada

Re: Gt750K resurrection - excessive smoke on right cylinder

Post by Salmanz8 »

Yea coolant level was reduced a bit.
I did removed the sris valve today, and some fluid came out, which also appeared to have some coolant in it.

Since the head gasket was weeping already, i dont mind taking the head off to inspect.

With good gaskets and seals, is there still a need for bars leaks ?
I did start the bike after draining all the coolant, and draining through the sris, and some colour changed to blue.
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Salmanz8
Posts: 65
Joined: Tue Mar 16, 2021 4:39 am
Location: Edmonton AB Canada

Re: Gt750K resurrection - excessive smoke on right cylinder

Post by Salmanz8 »

Decided to take the head off today.
Seems like the head had once been off before, and someone previously tried to reuse the head gasket.

Its a good thing i took it off, as the passages are very rust and crudy.
#3 cylinder has scoring, and some rust present, but i am not taking the cylinder off. Will run it atleast this season and see.
Pistons seem to have some play in the bores, but since i couldnt hear any noticeable slap, i will leave it be for now.
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Salmanz8
Posts: 65
Joined: Tue Mar 16, 2021 4:39 am
Location: Edmonton AB Canada

Re: Gt750K resurrection - excessive smoke on right cylinder

Post by Salmanz8 »

It also seemed to be leaking somewhat in number 1.
The center seems okay.
I am surprised that thing was even holding up.

One of the studs did come out with the head bolts.
I have all of those head bolts derusting at the moment.

The water jacket is all greasy.

One thing i cant figure out though, the combustion chambers for number 2 and 3 are smooth, like machined smooth.
But number 1 is very textured, almost looks peened ??
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Salmanz8
Posts: 65
Joined: Tue Mar 16, 2021 4:39 am
Location: Edmonton AB Canada

Re: Gt750K resurrection - excessive smoke on right cylinder

Post by Salmanz8 »

How likely is the base gasket/ o rings to contribute to the coolant making its way to the cylinder ?
bosco659
Posts: 21
Joined: Mon Aug 09, 2021 4:33 am

Re: Gt750K resurrection - excessive smoke on right cylinder

Post by bosco659 »

Checked my SRIS valves today. Center crankcase gas oil pooled up in it and the valve and line were plugged up. The left and right crankcases we’re clean and the valves were functioning properly.
1976 Yamaha XS650C, 1975 Suzuki GT750M
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