GS750 vs GS850

[Scudder]

I've got a 1978 gs750 and a 1980 gs850 (shaft drive). I ride both bikes equally as commuters everyday that it's not raining, or too cold (coming soon in Chicagoland) for a 40 mile roundtrip.

My issue is this. My 750 seems to have much better acceleration, agility, etc. My 850 is good on the expressway and on long trips, but it just doesn't have the gitty up that the 750 has. I've hand my 750 as a cafe racer, and my 850 has a fairing and bags, but I switched my cafe to a fairing and bags also from the colder months. It's a suzuki switchback, if you will. So the weight isn't too far off, I expect.

I suspect the BS carbs in the 78 vs the CV carbs of the 80 could have something to do with it.

Everything on both bikes is stock except for a modified exhaust on the 750. Could that make that big of a difference?

Any help in understanding this is appreciated.

Scudder

[Tim Tom]

Is your 850 an L?

L or not 850 is still much heavier even without the fairings and the bags. The drive shaft and pumpkin assemblies are much heavier than a chain and sprocket.

The listed weight for a stock '78 GS750 is 492 lbs. The 850 is a good 50-60 lbs heavier. Without any modifications. If you have given the 750 a cafe treatment, and stripped some more weight, then the difference will be even more apparent.

Also the wire wheels on your 750 will contribute to less unsprung weight, giving better performance all around.

[MisterCinders]

There is a third option for you with those two bikes.

Cross the streams.

[Steve]

GS750 is 492 lbs. The 850 is a good 50-60 lbs heavier.

That weight listed for the 750 is the "dry" weight.

The listed dry weight of an 850 is 557 pounds. Add in 5.8 gallons of gas (at about 6.3 pounds per gallon), weight goes to 593.
Add in a gallon of oil, a little bit of secondary drive fluid and fill the final drive, you are at the advertised wet weight of 603 pounds.

By the way, the dry weight of the 1000G was seven pounds less than the 850, the 1000E was 50 pounds less.

.

[Scudder]

It started out as an L but has acquired a G tank, and different handlebars. I think it's more of a hybrid at this point.

Sounds like the 750 has good reason to be quicker than the 850. The added "Huge" G tank probably makes a difference, as does the overall weight of the 850. The handling of the 750 is much better probably do to weight).

Thanks. I wasn't sure if it had anything to do with the carbs or if it was something simpler like a comparison in overall weight between the 750 and 850.

Scudder

[Nessism]

The bevel gears in the secondary drive and final drive eat up HP. Even if the bikes were the same weight, the shaft drive would be slower.

[Scudder]

Thanks. I feel better knowing this. My 850 is great on longer trips, smooth and comfortable. But... the 750 is so fast and handles so well. I guess I'm lucky to have the best of both worlds.

Scudder

[tkent02]

Put the 850 top end on the 750 and have the best of both worlds.

[Steve]

Thanks. I feel better knowing this. My 850 is great on longer trips, smooth and comfortable. But... the 750 is so fast and handles so well. I guess I'm lucky to have the best of both worlds.

Scudder

Enjoy what you have.

Some people will argue a bit, saying that the 650 was probably the best mid-size bike, because it makes almost as much power as the 750, but is a bit lighter and more nimble. Of course, that would be the 650E, not the 650G.

Many will agree with you on the 850 probably being the best of the shafties. The 1000 and 1100 had a little more grunt, especially down low, but tended to vibrate just a bit more, due to the larger rotating and reciprcating masses. This was offset a bit by lower engine revs at highway speed.

.

[MisterCinders]

Put the 850 top end on the 750 and have the best of both worlds.

Or just take the pistons and cylinder block from the 850 and add them to the 750.

He can use the 750 top end and carbs.

[havoK]

When I have to replace pistons, I am definately doing this to my bike

[dpep]

Just a couple of comments.

The 850 will definitely handle heavier than the 750 because it is, well, heavier. The 850 does not handle badly; it will just take more effort. It is most noticeable at take off and parking lot speeds. The 850 is also top heavy which adds to the load until you get it rolling.

The straight line performance should not differ a lot except right off the line. In the magazine evaluations of the time the 750 did mid twelves and the 850 high twelves, the difference mostly being at the start, again due to the additional weight. Cycle magazine reported it beating all 750's at the time (January 1981 edition) in a low speed roll on.

Of course those were tests of new motorcycles (with expert riders) not ones that have endured thirty years and possibly a succession of different owners. But they do give us some idea of what the bike can do if properly restored and operated.

One question I would ask is if you are talking about the 850's performance below 6000 rpm or above it. The bike performs pretty well below that number and sounds busy to most riders (me included). But it was actually engineered to run well, run safely and run long at higher rpms; it is almost a different bike. If you are comparing your two bikes at similar rpm levels and engine sound/feel you are probably running the 850 at least a gear too high.
...

[bwringer]

One question I would ask is if you are talking about the 850's performance below 6000 rpm or above it. The bike performs pretty well below that number and sounds busy to most riders (me included). But it was actually engineered to run well, run safely and run long at higher rpms; it is almost a different bike. If you are comparing your two bikes at similar rpm levels and engine sound/feel you are probably running the 850 at least a gear too high.
...

Sort of what I was thinking -- the 750 and 850 are likely geared differently.

You gotta spin that 850 engine. Make it sing!

[allojohn]

I suspect the BS carbs in the 78 vs the CV carbs of the 80 could have something to do with it.

Everything on both bikes is stock except for a modified exhaust on the 750. Could that make that big of a difference?
Scudder

You meant VM carbs on the '78 750, right? BS (CV) carbs are not stock.

[tkent02]

You gotta spin that 850 engine. Make it sing!

True on both, but more true on the 750.