850 final drive

[DannyB]

i have seen that a lot of members have done this mod. was wondering what the performance gains were.

[mro]

performance gains?

I've had an 850 FD sitting in my parts pile for years.
At first I did not install it because I decided to wait and see how it worked out for the guys who were doing the mod. Then between procrastination and just a lot of miles with the stock drive on several XSes I just never felt the need.

BUT

I have read the "testimonials" about better fuel mileage and the decreased rpm and engine noise while cruising. Seems to work very well for some. I guess how one likes it really depends on how and where you ride. Someday I might stick it on one just to see how it works for me... but I don’t have a problem with 5000+ rpm on the freeway and I normally get mid 30 to low 40’s MPG.

mro
BTW, this mod by itself it won’t make your bike any faster.
So maybe a little insight into where I’m coming from.
Stock cam chain tensioner works just fine for me as well as the octy on my specials.
I do have some mods on my hot rod XS, but the others are pretty much stock. Other than a little bling.

[petejw]

i havent done the mod myself,
but i thinks its a taller gearing,
so if anything it would cause slower acceleration
but a greater top speed.

[XSokieSPECIAL]

I have the 850FD mod and I like it a lot. It really isn't a "performance" mod it is more of a comfort mod.

Very comfortable if you do a lot of highway cruising as it drops your cruising rpm by at least 800rpms. That 6th gear that has been missing.

It will NOT make your bike faster at top end since the engine will be running fewer rpms at any given speed it will put less HP to the ground.

How fast do you NEED to go?

[XJOK2PLAY]

DannyB,

I just did mine a couple of weeks ago. I used an 850FD from a MNS.

I would say it all depends on how you're using your bike.
If your's is a stripped down, naked, town bike mostly... don't do it.

But, if touring's your thing, and your bike's a full blown bagger... and you take long trips or run the turnpike a lot... this is the SCHTUFFFF!!!!!
By all means, do it.

If, every time you shift through the gears, and you find yourself constantly trying to shift into the 'missing' 6th gear... then you need to do it.

If you're trying to increase touring range mpg's per tank, quiet down the engine noise, and give the bike a more relaxed highway ride... do it!

I love mine. Changed the whole personality of my XJ. BUT: I tour mostly, and run the turnpike at 80mph a lot!

You'll see around 800 rpm reduction on the highway.
I've seen a 2 mpg increase in fuel economy since I did the swap, too.

At 80 mph, I used to tach 5000 rpm. Now it tachs 4200.

Launches are slightly different, due to the taller ring & pinion gearing, but not all that big of difference.

As I said, if you've got a full dresser, this is the way to go. If you're looking for stop light to stop light, keep it stock.
Regards,
Bob

[DGXSER]

As my signature shows, prior to the XS11, I rode primarily CB750C. I was so used to the cruising type of bike that the high RPM at highway speed had me trying to shift into 6th. Since I changed to a 750/850 FD, I never look for another gear anymore.

My opinion and experience is that this mod does not produce any measurable milage increase. This mod does reduce low rpm pull especially in the upper gears, meaning you will find yourself downshifting out of 5th and even 4th more often. I do believe you can gain top end out of the bike by adding this gear, every one I have ridden ran out of RPM before it ran out of power in 5th. But really, who cares, the dang thing will go faster in either case than I have the cahonas to take it more than once anyway. And honestly, it has enough low end grunt that even the decreased pull is more than most bikes still.

I can also tell you that a fellow member here in the 'Nati has one installed after owning his bike since new and ridden over 80k miles. His riding style is very cruiser like. He has never had a gear slip issue because he rarely if ever gets on it hard enough to cause one. Anyway, he swears by the 750/850 Fd swap now.

I have always said since I put one on my bike that if you plan to go out riding through curvy hills trying to get the grunt pull out of the bike, then the stock FD is the way to go. Otherwise, the 750/850 is the bomb schnizzle!!

[DannyB]

thanks for info. i dont think this mod is for me. i have a deep love for the acceration of the xs's and xj's and would only want to improve it not hurt it.

[dbeardslee]

I've got a 750 FD on mine, and I'd never go back to stock. As far as performance, XSChop has said that when racing other XS's with stock fd's, they'll get him out of the hole, but while they're shifting into second he goes past and they never catch back up. Also takes your top end from somewhere around 125 to over 140. My $.02.

[petejw]

for the guys running the f/d mod
are you running 16 or 17 inch rear wheels?

[DGXSER]

Mine is a 16" Pete along with the other Special I mentioned which belongs to Steppenwolf. I know DBeardslee has a Standard with the 17" rear wheel.

[bikerphil]

for the guys running the f/d mod
are you running 16 or 17 inch rear wheels?

I run one of each. On my SF with 16\" rear wheel, I\'d have it no other way. On my F with the 17\", sometimes I switch it back to the stock unit, a bit more fun to ride that way. I\'m thinking of switching her over to the 16\" wider rim someday.

[petejw]

thanx for the responses guys, i was curious cause my bike
came with the 17" rim and rides well, ive often thought of going
the other way to a 16" rim for even more accelleration.