Toasty Final Drive

[conquest87tsi]

The inner race remained on the ring gear when removed to clarify.

Oh Wise Wizard of Trbig, I will succumb to your recommendations once I find a suitable XS850 final drive. I think the current one will manage a week on 80-90 and wheel bearing grease, especially if it's going to rain like this.

[trbig]

You can fill up 3+ final drives on one quart of the full synthetic, so in reality, you wasted money by buying the dyno oil. BUT... since the final drive looked like that, have you checked the middle drive? Filling the final and middle drive will take the bigger part of a quart.

[CaptonZap]

The inner race remained on the ring gear when removed to clarify.

.

Ya, alles ist in ordnung, mein lieberfreund.

The inner race stays on the ring gear hub, which makes it difficult to check clearance of the bearing, due to the mass of steel masking the subtle vibrations used to check clearance, and the ring gear riding on the pinion.
On the other hand, if you KEEP IT CLEAN, it is a beefy needle bearing, and if the oil level is kept to spec, it gets all the oil it needs to function till you get old and quit riding. Do not flush it out with anything but fresh solvent. Not the stuff in the solvent tank, which is full of microparticles of who knows what kind of abrasive dreck in suspension.
Cleanliness is next to Godlyness, and be God like in your dealings with the final drive.
Can I hear an "Amen", brother? CZ

[DiverRay]

Amen brother CZ

[conquest87tsi]

Trbig,
I did check and change the middle gear as well. I do think it is the first time the oil in either has been changed, since the amount of filings on the middle plug were identical to the final drive.

I am thinking I was just paranoid about the heat of the final drive, as it's sounds like they get quite hot. Anyway, I will get some good oil to fill my 750 final drive with when it goes on. At least my paranoia is going to result in close to 10mpg at cruising speed.

[natemoen]

10 MPG bump with the FD swap! You sir are dreaming!

[bikerphil]

Yes, the stock FD units get pretty hot, the 850 units not quite as hot. One thing I have noticed is with regular gear oil, over time there will be the normal buildup of metallic gunk on the drain plug, with the synthetic Royal Purple, none whatsoever, YMMV.

[DGXSER]

At least my paranoia is going to result in close to 10mpg at cruising speed.

I am a fan of the 750/850 FD swap. I like the reduced engine RPM, and never missed the torque. Ran one on my first XS11 for a couple years.

However, I never saw a noticable increase in fuel efficiency. It might give you a little, but I would suspect more in the 1-5 MPG range, closer to 2 or 3 if any. What fuel efficiency you gain in the area of lower rpm for the same speed, you lose some of in needing more HP for the same rpm due to loss of gear advantage.

[clcorbin]

What fuel efficiency you gain in the area of lower rpm for the same speed, you lose some of in needing more HP for the same rpm due to loss of gear advantage.

Your power requirements stays the same. Actually, the power requirements will drop a bit with the lower rpm due to reduced frictional losses in the engine and transmission. What does change is the amount of throttle needed to produce the required torque at that lower rpm. hp = torque*rpm/5252, so if you drop the rpm, then the torque must go up to maintain a constant rpm which means a more open throttle plate. And believe it or not, that actually helps your fuel economy by decreasing the loop loss in the engine (work the engine does to pull air into the cylinder past a closed off intake track).

Of course, whether this will lead to a noticeable fuel economy increase is a whole nother ball game.

[DGXSER]

Your power requirements stays the same. Actually, the power requirements will drop a bit with the lower rpm due to reduced frictional losses in the engine and transmission. What does change is the amount of throttle needed to produce the required torque at that lower rpm. hp = torque*rpm/5252, so if you drop the rpm, then the torque must go up to maintain a constant rpm which means a more open throttle plate. And believe it or not, that actually helps your fuel economy by decreasing the loop loss in the engine (work the engine does to pull air into the cylinder past a closed off intake track).

Of course, whether this will lead to a noticeable fuel economy increase is a whole nother ball game.

And here I was trying not to go all Enginerd on this thing. .

[clcorbin]

And here I was trying not to go all Enginerd on this thing. .

Sorry bud! I'll behave!

[conquest87tsi]

Well I do know what your saying about an increase in milage with the throttle plate open more, lessening pumping loss.

I also learned something.. Mileage comments really get people talking. Has to be up there with oil choices and hardtailing haha.

[CaptonZap]

Your power requirements stays the same. Actually, the power requirements will drop a bit with the lower rpm due to reduced frictional losses in the engine and transmission. What does change is the amount of throttle needed to produce the required torque at that lower rpm. hp = torque*rpm/5252, so if you drop the rpm, then the torque must go up to maintain a constant rpm which means a more open throttle plate. And believe it or not, that actually helps your fuel economy by decreasing the loop loss in the engine (work the engine does to pull air into the cylinder past a closed off intake track).

Of course, whether this will lead to a noticeable fuel economy increase is a whole nother ball game.

So that begs the question;
Has anyone ever seen a "Brake Specific Fuel Consumption" graph for the 11's?
That might shed some light on the 750/850 FD economy debate.
CZ

[motoman]

And here I was trying not to go all Enginerd on this thing. .

Didn't have to DGXSER,..............YOU got it right the first time.......