Gs75E 1983 smoking on one cylinder

[ned-999]

Hi, I've stripped my bike top end down and rebuilt it but I have one cylinder that is smoking badly. i am puzzled because the compression is ok @ 125 psi and not the lowest pressure by far. I've renewed the valve stem seals but this has not changed anything. If the compression is ok does that mean its not the rings that want replacing, and if so does anyone have any more ideas before I have to buy more gaskets again !!!!! Any help would much appreciated.

 

[Guest]

May be you broke a oil ring or have the ends of the rings lined up, or a valve seal popped off

 

[sharpy]

Ok what do you classify as rebuilding the top end. A full replacement of Gaskets, rings, cylinder hone, oil seals, gaskets and valve guide seals or just valve guide seals?

 

[hampshirehog]

Does your bike have the cam chain tunnel rectangular o ring? If the smoke is from one of the inner cylinders it's possible you squashed this on the rebuild.

Otherwise my advice is run it for a bit and see if it clears. If it doesn't you'll have to lift the top anyway.

 

[ned-999]

Hi. I replaced the rings, bottom and head gasket valve stem seals and cover gasket. As far as I can see the only way the oil can get in is through the valves or up through the piston rings. Thanks.

 

[Steve]

How do you know it's only one cylinder? :-k

Do you have individual exhaust pipes, like a Honda 750K or an early KZ900?

.

 

[ned-999]

Hi I know because its got no exhausts on at the moment

 

[Steve]

In that case, you might be better off by not running it at all.

There are rumors of valve damage if you run the engine with no exhaust pipes, I don't know how true they are.

.

 

[storm 64]

Dam, that has to be LOUD! Yeah, I think you can burn exhaust valves with running the engine with no exhaust system.

 

[blowerbike]

if it is the #2 cyl. smoking you may have a bad fuel valve.

 

[ned-999]

It is the #2 cylinder !! Can you please tell me where the fuel valve comes into the oil in the cylinder that I have. Thanks. Didn't know it had a fuel valve !!

 

[blowerbike]

#2 carb has a vacuum nipple that goes to the fuel valve.
when the valve malfunctions sometimes it let's fuel flow into the #2 carb intake and will foul the plug and make the bike smoke black normally...this will wash the rings out and wear the cyl. very fast.
put a vacuum cap on the #2 carb and the fuel valve on prime position and see it it quits smoking.

 

[tkent02]

put a vacuum cap on the #2 carb and the fuel valve on prime position and see it it quits smoking.

Then put the pipe back on and ride the snot out of it.

 

[ned-999]

Got it. Il be trying that thanks for you help il keep you posted.

 

[ned-999]

Hi. Well it's not the fuel valve. Made no difference. Il take Blowerbike's advise and get it back together and ride the hell out of it and see what happens. Think it must be the oil rings though as I can't think of any thing else it can be !!

 

[ned-999]

gs 750 smoking on No2

gs 750 smoking on No2

Well ive been driving it for a few weeks and the smoke and oil from No2 cylinder has stayed the same. So ive taken it apart again. I am at a loss as to why its happening, the rings were in place and the oil wiper ring was fine. When the rings are placed in the cylinder the end gap is in specification.

Ive renewed the valve guide seal.

Is there anywhere else oil could be coming from apart from the rings or the valves.

 

[Maddevill]

Did you check the cylinder to see if it was actually round? Maybe sometime in the past it got hot enough to warp your cylinder bore.

 

[WShie]

Piston rings installed upside down will cause oil pumping, as will loose valve guides even with new seals. I would measure cylinder bores, ring gap, piston clearance, valve guide clearance. You did measure before you put in new parts and after to make sure you were in spec?

 

[Guest]

I'm thinking valve guide too.
On the piston you will be able to see if oil has gotten by the rings.