Reverse fianal drive

[jmnjrpa]

Anybody do or thought about this? I have an 850 and an 1100 '81 MNS. I believe there may be a way to swap out the final on the 850 to an 1100 final drive. Since I have an extra drive of both and am in the middle of doing the conversion it occurred to me that it would give the 850 a lot more low end torque. If you burn em off the line bad most never check out your top end.

[Wildkat]

hey John,
we got a couple of our FDs from some of the triples guys that wanted to do this... Traded them their 750/ 850 FDs for the 1100s' FDs...
You might be able to check on their site to get a better idea of what they thought about the switch... not sure how many of them actually made the switch though...

JAT

[jmnjrpa]

Hmmmm

Thanks Kat!

[trbig]

Damn.. was hoping ol' John figured out a way to put reverse on the bikes..


Tod

[jmnjrpa]

Did

But you have a problem with roadrash on the a$$ when you brake hard! NOT cool!

[trbig]

Naw...

So far, the a$$ remains unscathed. Which is surprising considering the guys I ride with and share hotels with.


Tod

[Wildkat]

Thanks Kat!

You're welcome


I'm interested in how this turns out for you...
Keep us posted, please

[Montreux_Blue]

Did you swap it yet?

[jmnjrpa]

No

It will be a ways down the road as the bike needs lots of TLC to even run. According to my calculations the increase in torque /decrease in top end will be about 14%. That will limit the top to just under 110 MPH but it would get there a lot quicker.













The tank and seat are in good condition, just not mounted.

[Rev.Rick]

John. Am I understanding this right? The 750/850 final drive is a higher ratio than our 1100's, thus given a little less on take off, more on top end and improved mileage? I have seen many of the members on here have opted for the 750/850 final drive. I for some reason though that because of the difference in hp between the triples and our 1100's that the ratio on the 750/850's would be lower.

[jmnjrpa]

Gearbox

I believe the transmission would have to be considerably different as in more gears. The 3.3 ratio in the 1100 pushes torque over top end. When you reach top end on an 1100 your limits are really shortened by RPM (redlining) of the engine. Whereas the 2.9 ratio on the750/850 have less HP to begin with the gearing was so the bike would not be in last place but it does sacrifice torque. Hope this helps. Actually the drive line revolves 3.3 times for every rotation of the rear wheel on the 1100 but only 2.9 times on the 750/850. Higher (3.3) = more torque/less top end.

[fredintoon]

Lotsa reductions between the engine and the street.

John. Am I understanding this right? The 750/850 final drive is a higher ratio than our 1100's, thus given a little less on take off, more on top end and improved mileage? I have seen many of the members on here have opted for the 750/850 final drive. I for some reason though that because of the difference in hp between the triples and our 1100's that the ratio on the 750/850's would be lower.

Hi Rick,
recent posts say that the XS750/850 middle gear ratio is different too. Perhaps the primary reduction and transmission ratios as well?
What is needed is to compare the combined ratio between engine rpm and rear wheel rpm on both machines.
Maybe the XS750/850 engine does rev higher despite it's lower final drive ratio?
Gawd! All them gears! No wonder we lose all that power to transmission losses.
That's one reason the classic Britbikes can keep up as well as they do despite having far lower HP numbers.
An XS11 uses a Hyvo chain, 3 gear pairs and a driveshaft to put power on the street.
A Britbike uses two roller chains and you can't count the tranny because it's high gear is a friction-free lockup.

[Rev.Rick]

Thanks, John and Fred. I had a 1980 xs850 and it was pretty quik just for navigating around in town. I ran it WOT once and the best top end I could get was right about 110. I've done the same with my xs1100 and a little over 120 is all I could get. Whatever the gear combination is between the triples as compared to 1100's they seem to work equally well in both applications. I would not mind giving up a little on bottom end (I don't do burnouts. Tires cost too much) to gain something on MPG. My xs850 wasn't anywhere near as quik from 0-100 as my 1100, but it got way better mileage.