Whether or not an 850cc cylinder is a bolt on mod for an 8v GS750

[mattd1205]

Hi,

My ‘78 GS750 just started weeping oil from the head gasket. I’m considering dropping an 850 cylinder on it. I’ve been researching whether or not it’s a bolt on modification. Some extra grunt would be nice but I’m not terribly interested in grinding down the crankcase. Some folks say it’s a bolt on with ‘79-‘81, others say the ‘79 cylinders are a direct fit with no grinding on the case, others say the ‘79 cylinder requires less grinding etc etc. Is there a definitive way to predict which cases don’t require modification?

Matt

[Steve]

I have heard pretty much the same stories you have. Since I have never been directly involved in a similar project, I don't know for sure, but I have heard more stories about the earlier cylinders requiring less filing or grinding to fit properly.

Either way, it's not much that is needed. I have gotten the impression that it's something you can do at home, it does not require a machine shop.

.

[mattd1205]

I have heard pretty much the same stories you have. Since I have never been directly involved in a similar project, I don't know for sure, but I have heard more stories about the earlier cylinders requiring less filing or grinding to fit properly.

Either way, it's not much that is needed. I have gotten the impression that it's something you can do at home, it does not require a machine shop.

.

One guy on another forum on Facebook theorized that Suzuki used different casting molds over the production run. Some of the molds had the metal that needed to be removed and some didn’t. I guess it’s luck of the draw. I can’t verify that but it sounds plausible to me. I think I may just reseal mine.

[Rijko]

Some folks say it’s a bolt on with ‘79-‘81, others say the ‘79 cylinders are a direct fit with no grinding on the case, others say the ‘79 cylinder requires less grinding etc etc. Is there a definitive way to predict which cases don’t require modification?
Matt

According to Partzilla (link), there is no difference in cylinders for the 850G from 79-81.

This Suzuki 11210-45100 CYLINDER Not Available fits the following models and components:

Suzuki Motorcycle 1980 GS850GL Cylinder
Suzuki Motorcycle 1979 GS850G Cylinder
Suzuki Motorcycle 1981 TOURER - GS850G Cylinder
Suzuki Motorcycle 1981 GS850GL Cylinder
Suzuki Motorcycle 1980 TOURER - GS850G Cylinder

And this guy did it as a bolt on apparently : link

Interesting project :-)

0D05BD6D-73E4-482D-B45F-88D6C9349137-16593-00002A7053D8E678.jpg

[unfocused]

This is no different then punching out your 750 cylinders.
I researched this to death. It would improve the over-all if:
Use the 750 cams for better performance 850 cams if you plan on road trippin' - better economy and mid range
Jet the carbs accordingly and run a better air filter
Exhaust
The grinding on the crankcase is rarely needed and if it does, it's minimal. As mentioned before, it's a crap shoot.
The bores in the block need to be cleaned up to fit the 850 cylinder liners.

After all my research I stumbled across a 1000 engine and shoehorned it into the 750 frame.
Still have the 750 and I know where an 850 sits. Seriously been pondering a inline 4 dirt bike...