Is there any way to reduce 5th gear RPM on a 79 GS850

[chef1366]

I'm running a '83 GS1100 diff in my GS850GN. With the new 2.9-1 ratio, the engine rpm in 5th gear at 100 kph, dropped from 4500 to 4100.

If you want to further reduce the rpm in 5th gear, you need to split the cases and fit the higher ratio 5th gear set from a '83 onwards 850 or 1100. This change will reduce the rpm at 100 kph a further 400 rpm (3700). I have bought a new 5th gear set myself and will fit them to my spare engine, a monster big bore 850 project soon to be started.

You go Ian!
I'm painting the cases on Monday. I'm still asking the wifes forgiveness!

[49er]

You go Ian!
I'm painting the cases on Monday. I'm still asking the wifes forgiveness!

Hey Bill, it's always easier to ask forgiveness than to gain permission in the first instance! Besides, the making up is usually well worth it.

Ya haven't been using her oven to do the paint baking have ya?

[chef1366]

Hey Bill, it's always easier to ask forgiveness than to gain permission in the first instance! Besides, the making up is usually well worth it.

Ya haven't been using her oven to do the paint baking have ya?

A man has to know his limitations.

[Colin Green]

I'm running an '83 GS1100 diff in my GS850GN. With the new 2.9-1 ratio, the engine rpm in 5th gear at 100 kph, dropped from 4500 to 4100.

If you want to further reduce the rpm in 5th gear, you need to split the cases and fit the higher ratio 5th gear set from a '83 onwards 850 or 1100. This change will reduce the rpm at 100 kph a further 400 rpm (3700). I have bought a new 5th gear set myself and will fit them to my spare engine, a monster big bore 850 project soon to be started.

Hey Ian Cool 5th gear option, but my 85 GS1100G does 4000rpm at 100? does that mean that mine is an oddity? Did you also change your shaft when you put the 1100 diff in?

[Steve]

Hey Ian Cool 5th gear option, but my 85 GS1100G does 4000rpm at 100? does that mean that mine is an oddity?

No, being an '85, it already has the taller gear ratios. I think the 1100s also had some taller intermediate gearing, as they turned fewer revs than the 850s all along.

.

[chef1366]

Hey Ian Cool 5th gear option, but my 85 GS1100G does 4000rpm at 100? does that mean that mine is an oddity? Did you also change your shaft when you put the 1100 diff in?

KPH vs MPH ??

[49er]

KPH vs MPH ??

100 kph = 62 mph (approximate conversion).

[49er]

Hey Ian Cool 5th gear option, but my 85 GS1100G does 4000rpm at 100? does that mean that mine is an oddity? Did you also change your shaft when you put the 1100 diff in?

Giday Colin

As Steve has said, the 1100G gearing is already higher than the 850's. No need to change the shaft to match the 1100 diff unless fitting the 1100 engine to the 850 frame, which I haven't done.

[79GS850VETTER]

I never considered putting bar weights on. Do they make a big difference.

I've ridden this same bike for almost 200 000 kms over the past 31 years. Its not that I am "whining" like someone suggested, I would like to make the bike be it's best. It has a lot of sentimental value to me and I would like to ride it for a long time yet.

I am usually the guy in the pack using the most fuel as well so I would not mind trying a different trany or final drive and see what it does to the fuel milage.

49er, when you put the new gearing in and the new rear diff did it adversly affect your start up in 1st gear. It would seem that 800 rpm difference is about a gears worth. Would you compare the start up to starting in second with the old gears?

[49er]

I never considered putting bar weights on. Do they make a big difference.

I've ridden this same bike for almost 200 000 kms over the past 31 years. Its not that I am "whining" like someone suggested, I would like to make the bike be it's best. It has a lot of sentimental value to me and I would like to ride it for a long time yet.

I am usually the guy in the pack using the most fuel as well so I would not mind trying a different trany or final drive and see what it does to the fuel milage.

49er, when you put the new gearing in and the new rear diff did it adversly affect your start up in 1st gear. It would seem that 800 rpm difference is about a gears worth. Would you compare the start up to starting in second with the old gears?

I have only fitted the higher diff at this stage. No problems with starting in 1st gear. When I rebuild my spare 850, I will fit the higher 5th gear to it. I'm not expecting any problems with 1st gear then either. I'm expecting it will be equivalent to the 1st gear of my 1150 with both the diff and 5th gear changes together.

[Steve]

I'm expecting it will be equivalent to the 1st gear of my 1150 with both the diff and 5th gear changes together.

You are probably correct, as far as gearing is concerned.

The difference is that the 1150 has more torque, and is better able to handle the taller gearing.

.

[Nessism]

The 2.9 rear end does force more clutch slipping on the 850 but it's not too bad on a naked bike. If you are packing a load though it may be a consideration.

[Nessism]

Someone just posted a 1983 GS1100G in the Parts For Sale forum. Someone should swoop in and grab that rear end if they want the 2.9 ratio version.

[koolaid_kid]

I just went from a 15 tooth to a 16 tooth front sprocket, should get me 300-400 rpm drop at highway speed. Oh wait, you don't have sprockets.

The bar weights do make a difference. You can also make a homemade version of a bar snake. I did both on my KZ750 and it helped quite a bit. Brian ended up with my Manic Salamanders when it became evident the KZ was going to go away.

If you want to know how to make a bar snake, I can post it here in the tech section. There are a couple of paths you can take.

[IOWA450T]

DIY barsnake

I'd be interested in barsnake instructions