5 speed to 6 speed conversion?

[Anonymous]

I have a 1981 GS850GL, 5 speed. I am doing a full engine rebuild and am wondering if there is a way to upgrade my 5 speed tranny to a 6 speed to get more top speed. Were there 6 speeds in this vintage I can just get the trans gears and arms and drop them in?

[gsBert]

i dont know if the swap is possible. i do seem to know that you wouldnt necessarily get more top speed out of an extra gear. i know this from experimenting with my racecar, and i much preferred my 4 speed over the 5, less shifting... (not so much trouble on a bike though)

6 speed trannies have a closer gear spacing but the 6th is usually very close to what your 5th would be. the tighter spaced gears are so you can keep in the power range easier for engines with a peaky torque curve.
your bike has a relatively flat torque curve (that's a good thing).

you can increase your top speed (at the cost of slower acceleration) by changing the final drive ratio. on a chain bike you jsut change to a different sprocket size, on a shaftie, you can change the gearing either at the transmission output or at the wheel. i don't know what your gearing is and what (if any) other gearings exist that fit your bike. sorry.

are you really redlining it in fifth? if so, stop doing that, some places have speed limits...

[humhead]

Your gear choices for a GS shaftie are very limited. The stock final drive ratio is 11/34. 83 & 84 GS1100g & GKs use a 11/32 final drive.
The six speed trans is just about impossible. The 850 (like all GS bikes) has a
"unit" engine & transmission (the engine & trans are toghther in one case) Upgrading to six speeds would require fabricating new gearsets, shift forks, shift cams. etc. that would fit in the 5 speed case & still handle the HP/torque of the 850 motor.


Terry

[Anonymous]

Thanks for the info. I haven't actually been redlining 5th, I'm just trying to get everything I can out of this engine in the ground-up build. It's a low milage motor from what I understand (last owner was not firing on all four pistons and the speedo looks non-stock with it's 8300 miles and broken cable) and was acting like it was being restricted at highway speeds (65-70). When I broke down the motor, cylinders 3 and 4 were pretty nasty so that would explain the power loss feeling, 1 and 2 were doing all the work. The carbs have been rebuilt and I am about to get new valves to replace the burnt ones and have a 3 angle valve job done.

Again, thanks

[humhead]

Getting all four cylinders to fire should make a huge difference. Be sure to check the carbs & ignition. The 11/32 final drives are rare, but you should enjoy your bike now that it's healthy. If a 11/32 final turns up GRAB IT!

[Anonymous]

I must say if you have lots of power you might find a new rear sprocket your top end will go up. I found this on my old 450. I could still beat any car off the line and I could keep up with other bikes on the freeway. The bigger you go the slower you hole shot speed but shear power will over compensate.

[KGB]

"G" models are shaft drive, so he's very limited in changing ratios.
No chain/sprockets with the shaft drive.