Performance parts for gs850g.

[Moarpower]

Just curious about what performance engine parts are available for the 850g.

I bought a bike with a claimed 11-1 high compression rebuild done but I'm unable to find evidence to support that claim nor can I find many parts online for the 85og.
The are lots for the 750 and 1000/1100 but the 850g seems like the forgotten stepchild when it comes to upgrade parts.

I need to pull the head and replace gaskets etc and would like to add new pistons and rings, valves and spring upgrades.

[Burque73]

Search for an 1100G engine to throw in your 850's frame. That's about the only way to get more out of it, I think.

Edit: Depending on what year 850 you have that may not work.

[Moarpower]

Search for an 1100G engine to throw in your 850's frame. That's about the only way to get more out of it, I think.

Edit: Depending on what year 850 you have that may not work.

The current project is a 1980

[zed1015]

I bought a bike with a claimed 11-1 high compression rebuild done but I'm unable to find evidence to support that claim

Once you pull the head it will be obvious whether the pistons are higher comp.
Either that or do a comp test when warm and see if the readings are substantially higher than stock.

[Moarpower]

Once you pull the head it will be obvious whether the pistons are higher comp.
Either that or do a comp test when warm and see if the readings are substantially higher than stock.

Compression test read 155, 155, 155, 160 and the rebuild was done in 2016. Good compression but not overly high

[bwringer]

Compression test read 155, 155, 155, 160 and the rebuild was done in 2016. Good compression but not overly high

Those are extremely healthy numbers. No way I'd take that apart.

According to my Haynes manual:
Stock compression ratio is 8.8:1
Compression range is 128-171 psi, service limit is 100psi, and maximum difference is 28psi.

The question of high-performance 850 comes up here fairly regularly, and as far as the GSR Hive Mind can tell or remember, there really aren't any performance parts made, now or in the past, for the 850G/GL. A few have installed 4-1 exhausts and pods, then entered the usual carburetor hell for a while to make them work.

For a time, you could get 1.0mm oversize pistons from Suzuki and bore the cylinder liners.

There have been a few isolated projects here and there where folks have had custom pistons made, widened the wheels, etc. But that's all very much at the deep end.

As noted above, the best route is to slide in a 1000G or 1100G engine. There's some sorting out to be done of the airbox (if you use one), and exhaust, and driveshaft (make sure you get the driveshaft with the donor engine), but overall it's been done several times. You get a nice bit of added performance, and the larger engines are actually somewhat lighter; the 850 engine is the heaviest of all the shafties.


In the end, what is your goal? I'd argue that a lot of folks have simply never experienced an 850 that's running correctly. Getting everything up to snuff and perfect in stock form is step one, so you understand what you're starting with.

Another interesting phenomenon is that a lot of folks haven't figured out that a properly running 850 loves to spin. It's a far more entertaining engine (in my opinion) than the 1000 or 1100 because you have to keep it on the boil. That rush from 6,000 to 9,000 rpm is serious fun, and seriously addictive and involving. Grip it and rip it. Spin it to win it...

[Moarpower]

Thanks Bwringer.

The reason for the work is just in case I need to.ooen it up. It slipped time and I will want to remove the head and check valves and the piston tops at a minimum. If they are fine I won't need to do any more besides resetting timing.
I believe I may need a new timing chain also but hopefully it's just the failed tensioner.
Cam timing will need to be degreed in as they have slotted the cam gears.
I bought this bike already with pods and a 4 into 1 exhaust.
I put the stage 3 jet kit in from Dynojet but other issues with the bike have prevented me from really dialing it in nicely.

[GregT]

When you pull the head to check for damage,measure the bores. It's possible it may have 1000 pistons.

[rphillips]

Hope your problems aren't as bad as you're thinking. With the compression you're seeing very unlikely you have valve or piston problems. Also that EX. cam gear on the IN cam has got to be straightened out. Your cam degreeing could be forgot about if you can find a set of oem cam gears or a set of cams, with oem gears on them. Just install them per manual and all should be good. Also like someone else said, check your tensioner, they rarely give problems, other than oil leaks,. Locking them down to make a manual tensioner out of them has been done a lot, if that's happened, it will no longer keep tension adjusted automatically.... I've always thought easiest, cheapest things first, then go deeper if needed..

[unfocused]

The GS850 is a shaft drive so the only option is to swap with another shaft drive engine or upgrade the top end. No performance options however, a stock 850 will wake up with a set of 750 cams, exhaust and upgraded air filter(s)... DO NOT order any gaskets until you seperate the jugs from the engine. I did this with my 750 only to find out it was already bored to an 850.

[Moarpower]

The GS850 is a shaft drive so the only option is to swap with another shaft drive engine or upgrade the top end. No performance options however, a stock 850 will wake up with a set of 750 cams, exhaust and upgraded air filter(s)... DO NOT order any gaskets until you seperate the jugs from the engine. I did this with my 750 only to find out it was already bored to an 850.

What will the trade off be if I use the 750 cams?

[unfocused]

What will the trade off be if I use the 750 cams?

You will see the power increase through out the power range. From what I understand through research, the 750 has the better cams within the 8V engine line. The G engines are kinda lazy. It's been reported that even the 1000 will wake up with this cam swap.

Also, you'll need to look into the engine to see if it's been overbored or pop up pistons. You say high compression. This would require pop up pistons or a shaved cylinderhead. Just over boring the engine will not increase compression.

[pdqford]

Just over boring the engine will not increase compression.

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[unfocused]

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I'm sorry, did I say something that offended you?

[pdqford]

I'm sorry, did I say something that offended you?

No, you didn't say something that offended me.
I'm sorry if I implied that by using the wrong emoji..
But increasing the bore does raise the compression ratio.