Final Drive Swap Poll

[3Phase]

You should be fine, Skids. A little too loose is better than a little too tight. You're not going to get factory-new specs on a used final drive with a used crush washer anyway but it should be in the low to middle ranges unless the drive is worn out.

If the bearing preload is good but the pinion nut isn't tight enough to stay in place it will slowly back off until you get loose-shopping-cart-wheel syndrome on the final drive coupler/pinion shaft and it will eventually destroy itself.

Set the preload a fine frog hair under spec on the pinion bearings and use blue Loctite on the pinion nut if you're concerned about it coming loose while you ride; red Loctite if you're totally paranoid or just plain batspit crazy and make sure your OSHA red Loctite permit is complete and up to date before you sell the bike to anyone else.

[James England]

It depends ... do you know if you have a Type I or a Type II 750 final drive and exactly how did you arrive at that 90 ft/lbs of torque??

I have the Type I. I put the FD on the rear wheel (off the bike), held it with a wooden lever and tightened the pinion nut (no crush washer) with a torque wrench. At first I went to 100 foot pounds but the drive seemed to tight compare to the OEM one, so I backed it off to 90 and it felt right............

[3Phase]

James, over-torquing anything to set clearances or preload is not a good idea. The damage, if any, will have already been done so without checking the final drive myself there is no way I can tell you if it will be okay. You will have to decide.

Yamaha specified 54 - 61 ft/lb (7.5 - 8.5 cm/kg) of torque for the Type I final drive coupler/pinion nut.

You used 100 ft/lbs and discovered that the pinion was too tight so you backed off to 90 ft/lbs:
100 ft/lbs is 39 - 46 ft/lbs (5 - 6 m/kg) too tight.
90 ft/lbs is 29 - 36 ft/lb (4 - 4.9 m/kg) too tight.

The next time you're in shop, ask a mechanic (a mechanic, not the wall-eyed goober in the back corner of the shop washing parts, licking windows and making balloon animals out of his protective gloves) if it would be okay to torque the main bearing and connecting rod bolts in your engine an extra 39 - 46 ft/lbs, rotate the crankshaft to see if it will still move, back off the torque to only 29 - 36 ft/lbs too tight, then give it a test run instead of using all that complicated dial indicator/micrometer/oil clearance/plastigauge/torque spec stuff written in the fine manual.


Type I and Type II final drive coupler nut/pinion bearing torque and preload

Type I: Set preload with a dial indicator and shims. Shim sizes in steps of 0.0008in (0.2mm).

Specified Torque: 54 - 61 ft/lb (7.5 - 8.5 m/kg) = 7 ft/lb (1 m/kg) tolerance

Bearing Preload: 9 - 10 in/lb (10 - 12 cm/kg) 1 in/lb (2 cm/kg) tolerance


Type II: Set preload with expansion spacer (crush washer), not shims. Torque nut to set preload.

Nut tightening torque (for reference): 72 ~ 108 ft/lb (10 ~ 15 m/kg) = 36 ft/lb (5m/kg) range

Preload: 3.4 - 4.3 in/lb (4 - 5 cm/kg) = 0.9 in/lb (1 cm/kg) tolerance


So, basically, the final drive lash and preload should be checked when you obtain the final drive, before you start removing parts from your bike and definitely before removing the coupler nut from the pinion shaft. The tests in the XS1100 service manual are for the Type II final drive so the torque values are not entirely correct for a Type I drive but they are similar.

You will be able to tell if you have a good or a bad drive before you spend a lot of time and effort trying to make a silk purse out of a sow's ear or make a sow's ear out of your new silk purse.

[James England]

James, over-torquing anything to set clearances or preload is not a good idea. The damage, if any, will have already been done so without checking the final drive myself there is no way I can tell you if it will be okay. You will have to decide.

Yamaha specified 54 - 61 ft/lb (7.5 - 8.5 cm/kg) of torque for the Type I final drive coupler/pinion nut.

You used 100 ft/lbs and discovered that the pinion was too tight so you backed off to 90 ft/lbs:
100 ft/lbs is 39 - 46 ft/lbs (5 - 6 m/kg) too tight.
90 ft/lbs is 29 - 36 ft/lb (4 - 4.9 m/kg) too tight.

The next time you're in shop, ask a mechanic (a mechanic, not the wall-eyed goober in the back corner of the shop washing parts, licking windows and making balloon animals out of his protective gloves) if it would be okay to torque the main bearing and connecting rod bolts in your engine an extra 39 - 46 ft/lbs, rotate the crankshaft to see if it will still move, back off the torque to only 29 - 36 ft/lbs too tight, then give it a test run instead of using all that complicated dial indicator/micrometer/oil clearance/plastigauge/torque spec stuff written in the fine manual.


Type I and Type II final drive coupler nut/pinion bearing torque and preload

Type I: Set preload with a dial indicator and shims. Shim sizes in steps of 0.0008in (0.2mm).

Specified Torque: 54 - 61 ft/lb (7.5 - 8.5 m/kg) = 7 ft/lb (1 m/kg) tolerance

Bearing Preload: 9 - 10 in/lb (10 - 12 cm/kg) 1 in/lb (2 cm/kg) tolerance


Type II: Set preload with expansion spacer (crush washer), not shims. Torque nut to set preload.

Nut tightening torque (for reference): 72 ~ 108 ft/lb (10 ~ 15 m/kg) = 36 ft/lb (5m/kg) range

Preload: 3.4 - 4.3 in/lb (4 - 5 cm/kg) = 0.9 in/lb (1 cm/kg) tolerance


So, basically, the final drive lash and preload should be checked when you obtain the final drive, before you start removing parts from your bike and definitely before removing the coupler nut from the pinion shaft. The tests in the XS1100 service manual are for the Type II final drive so the torque values are not entirely correct for a Type I drive but they are similar.

You will be able to tell if you have a good or a bad drive before you spend a lot of time and effort trying to make a silk purse out of a sow's ear or make a sow's ear out of your new silk purse.

Yes, I was going on the torque setting mentioned in the tech tips which mentioned the figure which applies to the Type 2. I didn't realise mine was Type 1.

I'll probably take the FD off and re-check the bearing torque. Somehow, I think it's going to work out OK though, with no damage done. The drive felt tight, I backed it off and it felt fine. I've run the bike a lot since then and not heard any noises or felt anything odd. Tapered roller bearing do take a lot of punishment, I've found/ Incidentally, when removing the pinion nut (I used a torque wrench), it took 120 foot pounds to get it off! Gulp!

Having said all that, the drive does feel fine and runs well at the moment, so I'll not get too paranoid re having damaged it but.... I'll definitely go and re-do that nut tomorrow......

[James England]

Since I made the last post, I took the FD off and checked the pinion nut torque. Now torqued to 60 and all would appear to be fine! If I hear any funny noises or whatever, it'll be easy enough to get hold of another FD cheaply. I don't think I'm going to need one though....

I wonder if the tech tip should be modified though, to include the two types of 750FD and the relevant torque settings?

[3Phase]

Right on, James! Way to go! I'm glad it didn't hurt that beautiful drive!

I think XSChop, Cody, and everyone else involved did a great job on the research, writing, and pictures for the Tech Tip and it looks like everyone was pretty stoked at the time.

I agree that the torque for the Type I and Type II coupler/pinion nuts should be mentioned somewhere in the Tech Tip, maybe a picture showing the two side-by-side to eliminate any confusion, but it is well written and illustrated. And it does look like there's a missing character in Cody's addendum to the Tech Tip: "On a type it is about 10 inch pounds." should be "On a Type I it is about 10 inch pounds."

Because I was and still remain highly skeptical about the wisdom of exchanging stock parts that spin less than two feet from my backside with parts from a smaller, lighter, less powerful bike I did a lot of searching and reading before I bought a drive to do the mod. Eventually I found the Yamaha shaft drive service PDF and poured over it until I understood what it was trying to tell me so I was already well aware of the differences when I was doing the test and setup work.

That worked out well for me because the pinion nut on the drive I bought had been overtightened (I have no idea how and neither did the seller) and the coupler would barely turn when I took it out of the box. It is a Type II final drive so I took the whole drive apart and went over it with some gear paint and a fine toothed magnifying glass to make sure it was a good drive and not a boat anchor or an exotic doorstop. I bought a new crush washer from Yamaha, set the preload, put it all on the bike and I've been riding it ever since.

I'm leaving for Las Vegas tomorrow morning at 3 AM to beat the traffic, then heading down to Arizona to put in a solar powered well. I'm not sure about me at that time of morning but I'm sure the final drive will be just fine.

[James England]

to put in a solar powered well

I like the sound of that. Have a good trip, 3-Phase

[planedick]

My final

I've had my mod for a long time. No problems at all and I love it. I do lots of super slab riding so the lower RPM's or feeling like I got a 6th gear is perfect. I hear that some are getting better mileage! I can't imagine how that happens. Anyone who is educated in physics will tell you that's not going to happen. It takes the same amount of energy to push against the wind no matter what type of gearing you use. Lower RPM's means a slightly bigger "fire" in the chamber but fewer per mile, and higher RPM's means a smaller "fire", but more of them per mile, so the energy use is the same. I realize there will be a few that will argue and say that they get better mileage, but that is an opinion, not proven fact. If you don't think I'm right, just go ask the college professor who teaches these things. I've been riding with mine for a long time, got 30 - 33 MPG before the mod and the same after. No change.

[skids]

(snip) If you don't think I'm right, just go ask the college professor who teaches these things. I've been riding with mine for a long time, got 30 - 33 MPG before the mod and the same after. No change.

To tell you the truth, mine only changed a couple of mpg. I suppose the energy lost to work for the pistons and other components sliding through the oil must come into play somehow. You know, lower rpms means less distance travelled. I just enjoy the longer distance rides more with the engine howling a little less.

[Bonz]

Can't argue with physics... supposedly... but I do see a 2 mpg improvement since my FD swap.

Physics in the pure sense are non negotiable, they are what they are. However, when it comes to internal combustion it's all about the carbs and engine, how they are working together with the gearing.

Yeah, it does take the same energy to move down the road at any given speed, however there are more efficient (or less efficient) engine speeds, and running an engine faster creates more piston speed (more stops and starts of the piston for a given road speed, friction), more crankshaft rotations through the oil sump (more drag) and those are independent of the energy to move through the air and down the road.

All things equal, unless the particular rpm you run at is the engines exact "sweet spot" where the engine is operating at peak efficiency in terms of power, rpm, throttle opening and/or a combination of those that mesh well together, a moderately lower rpm that does not stress (lug) the engine should yield better mpg numbers, and I've seen that with my bike unequivocally.

All this is independent of the wider transmission ratios the FD swap gives that allow for less shifting in city traffic in my experience, and on/off throttle transitions to shift will use more gas than steady throttle or normal roll on/roll off throttle manipulation to adjust speed in any one gear vs. shifting between them.

What I do know is the XS engines as a whole are not in a nominaly usefull rpm range when below 3,000 rpm when it comes to cruising or accelerating (in my opinion), and I have to dial in more throttle to maintain speed in a taller gear below 3k as opposed to keeping it in a gear that gives 3k rpm or a bit more for cruising the same speed. Mpg will be lower when using too tall a gear and dialing in more throttle.

So, with all that said, I don't use any more throttle opening to cruise down the interstate at 75 mph with the FD swap than I did before when the bike was running 500 rpm higher at the same speed with the stock FD. I would say I use less by virtue of the observation that I can keep the engine on the edge of on/off throttle more easily for a given engine speed now that the engine braking isn't nearly as abrupt as before when turning 500 rpm more with the stock FD. Again, smoother transitions with the throttle, independent of the engine speed itself will increase efficiency of gas useage. My opinion is the FD swap allows smoother and more efficient use of all the variables used in riding, thus that is what helps boost mpg along with the lower engine speed.

And, by no means do I sense at 75 mph in 5th gear that I'm anywhere close to being in too tall of a gear. I did feel I was 1 gear short before the FD swap though at 75 mph. I've said before, and I'll say it again, that 4th gear post-swap has the engine turning 100 rpm or a bit more at 60 mph than it did in 5th gear before the swap, so I have my back road gearing more or less right where it was before, with the added benefit now of lower rpm and no less useful or less noticeable bike performance at higher modern speed limits.

What would be really helpful, is if someone could post a dyno chart for a stock, well tuned XS1100 to see the power curve, and note any differences in power output at the before and after rpm. I think I was able to find one dyno chart on the forum when doing a search, and that had some big dips in it because the bike hit some really rich spots at a couple points in the rpm scale. I suspect we'd find the torque curve is pretty flat from about 3,000 rpm and above, and if the bike is running 500 rpm less, producing the same amount of torque or close to it (couple of ft/lbs either way), then a lower rpm producing the same torque would get the job done more effiiciently.

Ok, with all that, I make the claim to not be a physicist or rocket scientist, just fascinated with internal combustion and good beer and scotch.

[planedick]

Other factors

There are other things that will change your total mileage. What I'm saying is that at a given steady speed, the energy consumed is the same for each final. I mean for instance, steady 65 MPH on a level surface will consume the same amount of fuel with both finals. Starting from stop will change, and how you do it might change too. Maybe you liked the G forces on take off with the original final but don't do that so much with the mod = better mileage... These XS's can get really great mileage if you cruise along at a steady 50 MPH, nearly 40 MPG, making 200 mi on a tank of fuel possible.

[Bonz]

Planedick,

I understand what you are saying, however given the riding I've done in over 3500 miles with the stock FD, and about 500 miles with the FD swap, my mpg has gone up 2 mpg. Most of that is on the same commute back and forth to work, 34 miles a day round trip. 26 miles of that commute is on the interstate at 75 mph, the rest of the 34 miles is the same route on 2 lane roads getting to and from the interstate.

It is apparent that the XS is running more efficiently for my kind of riding at the same speeds, therefore overall energy required is a bit less.

The key is it does not take the same energy (gasoline, energy consumed as you termed it) to do the same work regardless of FD persuasion.

Work is the output function of the gasoline fed to the engine, and it takes less gas to do the same work. More efficient at lower rpm at higher speeds is the only way to define it as I doubt the 2 mpg increase is a result of any change in warm up, shifting, stopping, accelerating, etc on the type of riding I'm doing since 95% of the ride is at speed and the routine is the same day in and day out. Therefore the increase in gas mileage, albeit only 2 mpg, but none-the-less a measured and real change.

[cowboybob998]

bumbell be

I've had my mod for a long time. No problems at all and I love it. I do lots of super slab riding so the lower RPM's or feeling like I got a 6th gear is perfect. I hear that some are getting better mileage! I can't imagine how that happens. Anyone who is educated in physics will tell you that's not going to happen. It takes the same amount of energy to push against the wind no matter what type of gearing you use. Lower RPM's means a slightly bigger "fire" in the chamber but fewer per mile, and higher RPM's means a smaller "fire", but more of them per mile, so the energy use is the same. I realize there will be a few that will argue and say that they get better mileage, but that is an opinion, not proven fact. If you don't think I'm right, just go ask the college professor who teaches these things. I've been riding with mine for a long time, got 30 - 33 MPG before the mod and the same after. No change.

A bumbell bee cant fly, but it does, physics ? the only way you are going to find out if the FD swap is any better on MPG is to do a wind tunnel test before and after on the same machine, comon sence tells me from messing around cars and bikes all these years is that the gear swap is still in the actseptble range of power to ground, i beleave the only reason it was so low of a gear is that yamaha wanted the fastst bike in the 1/4 mile, heres my 2 cent worth,

[3Phase]

I got 44 mpg doing 70-75 mph on the ride out to Las Vegas yesterday. The 750 FD helped.

[Bonz]

The 80 SG is responding well to the swap. 133.8 miles, 3.3 gallons. 40.5 mpg on the last tank for my standard, day-in, day-out commute.

Never seen more than 37 mpg for the commute, mostly interstate, so looking good at this point for the desired results of increased mpg, and more relaxed running.