Final Drive Swap Poll

[3Phase]

Don't get cocky

Looking at the previous posts, I'd say it isn't a problem because there have been no posts about it and people have done thousands of miles with the swap.

James,

I doubt a 750/850 final drive would survive nitrous! I discovered problems with the XS1100 final drive setup on my stock '80G and I guarantee that a 750/850 final drive is not as sturdy as the 1100 final drive. If you don't make drag starts or pop the clutch to do wheelies the 750 final drive will last for a long time.

One of these days, hopefully before the final drive finally breaks, I'm going to take the 750 final drive apart and re-check the lash, ring and pinion contact patterns, the bearings and the bearing races. I set up and checked everything in the 750 final drive before actually putting it on my bike so I will be looking for worn yoke splines; sloppy u-joint; a crushed crushed washer; stress cracks in the aluminum input shaft and ring gear housings; input shaft bearing and race wear; increased gear and bearing lash. I expect to find a slightly wider, smeared, contact pattern on the ring and pinion gears from the smaller 750 ring gear flexing and sliding away from the input pinion gear under load but right now I have other things to do than to tear into a running bike and make it a not-running bike.


On the original XS1100 final drive setup on my '80G both the drive shaft lower splines and the final drive input coupler were damaged, the final drive input shaft housing was scored. After seeing the damage to the original XS1100 final drive setup and looking at the physically smaller components in the 750 final drive I did not trust it. I still don't trust it entirely but I change the final drive oil regularly and keep all of the splines greased and it has run without any audible or visible problems for over 30,000 miles. I do have a couple of spare XS1100 final drives in case the 750 final drive breaks.


I did a search of the forums and found a couple of threads with pictures of the damaged original XS1100 drive shaft and input coupler that I found on my '80G both before and during the 750 final drive swap.

Drive shaft lower end spline out-of-round damage:-

Who Ya Gonna Call? Grease-Busters!


Input coupler/input shaft 'flex' damage:-

Better XS11 u-joint for 750 final drive


The 750/850 final drive swap works and it works well but it is not as sturdy as the original 1100 final drive.

[James England]

James,

I doubt a 750/850 final drive would survive nitrous! If you don't make drag starts or pop the clutch to do wheelies the 750 final drive will last for a long time.

The nitrous is long gone and I wouldn't bother with it again. No, I won't be doing drag starts or wheelies. I just want a reasonably fast, classic looking bike which runs at a relaxed pace in an under-stressed way. If you've managed 30,000 miles on the 750FD, I hope to as well, given my riding style (boring).

Like you say, the 750FD isn't as beefy but I would agree that, if looked after, it should be OK. Time will tell. Like you, I've kept the OEM FD just in case. That's assuming that, in the event of an FD explosion, I survive.....

[James England]

The 750/850 final drive swap works and it works well but it is not as sturdy as the original 1100 final drive.

I'm wondering what aspects of the 750FD are not as sturdy as the 1100FD.

I found exploded diagrams of both drives:

XS1100

http://images.cmsnl.com/img/partslis...03e-8_2d33.gif

XS750

http://images.cmsnl.com/img/partslis...56f-7_ddc5.gif

Looking at the two diagrams, I don't see any major differences in (visual) 'sturdiness'...... if anything the 1100 driveshaft looks stronger at the rear end but we're using that one, right? There appears to be a difference in the casting of part number 25 in each drawing, with the XS11 one looking slightly beefier? But, to me, this looks an interchangeable part with the one on the 750FD. Maybe?

Given the similarity of the drawings, I doubt somehow that Yamaha would use lower specification bearings, or seals or whatever. I've been looking at the part numbers for each drive. Many are the same....

eg part number 17 in both drawings is still available and is part number 2H74610200. in both cases. Same with part 19 (1J746106N0), part 11 in the XS11 drawing is part number 9333200079. This is the same part number as part 10 in the 750.

[3Phase]

I'm wondering what aspects of the 750FD are not as sturdy as the 1100FD.

James, as I started checking and adjusting the 750 drive I thought about taking pictures of the internal parts and the procedure but I decided against it.

There is already a PDF from Yamaha that describes the process of testing and adjusting both Type I and Type II middle and final drives in excruciating detail and I would have had to clean my hands every couple of minutes so I wouldn't contaminate my mobile phone while using its camera. I really, really, (really!) did not want my phone to smell like old gear oil so I left it in the house and didn't bring it anywhere near the garage until I was finished. I will try to take some pictures the next time I take the drive down for inspection.

If you look closely at the part diagrams you will see there are no part numbers for the pinion shaft or the ring gear and they are not described. The pinion shaft housings have different part numbers and the final drive housings have different part numbers.

The exploded drawings don't show it very well unless you've actually seen the parts and know what to look for: the 750 pinion shaft/gear and pinion bearings are smaller; the 750 ring gear is smaller and thinner.

It's similar to grafting a 1/2-ton truck (lorry) rear end into a 1-ton to lower the engine RPM and get better gas mileage.

[James England]

There is already a PDF from Yamaha that describes the process of testing and adjusting both Type I and Type II middle and final drives in excruciating detail

I'd be interested to read that... do you have a link?

I understand what you mean re the pinion etc being bigger. I suppose it depends just how accurate the stress calculations were on the 750 FD and how much margin there is in the components strength. As you mentioned before, taking it steady and not doing daft things will probably mean the drive will last........

[3Phase]

James, it looks like Catatonic Bug has the file on his web site:-

www.ringler.us/xs1100/ShaftDriveManual.pdf

Take care of that 750 drive and you'll have a lot of fun with it.

[James England]

James, it looks like Catatonic Bug has the file on his web site:-

www.ringler.us/xs1100/ShaftDriveManual.pdf

Take care of that 750 drive and you'll have a lot of fun with it.

Nice one. Thanks. That's the sort of information you don;t get in the Haynes manual.

I didn't check my pinion nut with an inch pound torque wrench though. I just tightened up the nut up to 90 ft/lbs...... reckon it will be ok?

[cywelchjr]

James, it looks like Catatonic Bug has the file on his web site:-

www.ringler.us/xs1100/ShaftDriveManual.pdf

Take care of that 750 drive and you'll have a lot of fun with it.

That's I think the point. Mechanical components will take a LOT of abuse if you don't do things like pop the clutch. If loads are put on in such a way as to get on it AFTER the slack is taken up, you can put a LOT more stress on it without damage than if you don't take up the slack first.

One of the things I learned as a teenager (scary thought huh?) was there is a BIG difference between dumping the clutch without getting it partially engaged first to take the slack out of the drive train first and dumping it after it's partially engaged and the slack is taken up and the suspension is loaded up as well, you can put a lot more power to the wheels without breaking or damaging anything. I'd think the same it true here. If you dump the clutch to do a wheelie, you are likely to cause damage, for sure to the 750 FD, and maybe even to an 1100 FD, but if you do a power wheelie done only with the throttle, there is a decent chance it would handle it ok if you didn't do it too often. Frankly, I don't plan on doing either one. I think the 750 FD has plenty of strength and all for my type of riding with regular fluid changes with good quality synthetic gear oil.

[Bonz]

Gear (oil) question... Heck, back in the day the XS was hatched, was synthetic gear oil much of an option? I was just a young 'un back then.

For you guys that run a synthetic gear oil, do you notice any difference in the FD housing temp after a ride compared to dino oil? I have found the 750 FD feels cooler relative to the stock FD in general, but on hotter days (had one so far since doing the swap, 75+ degrees) the 750 FD was plenty warm, so can't say when the weather gets into the 80's and 90's I'll be able to tell a difference in temp. Anyway, anyone have any experience with a cooler running FD (swap or not) when using synthetic gear oil?

[cywelchjr]

Yeah, I didn't use a temp gun or anything, but it ran cooler to the hand on the 1100 FD with synthetic over dino, and the 750 FD runs cooler than the 1100 FD, but I also went direct to synthetic with it when I installed it. I'm worried about clutch slip with the engine and synthetic with our clutch material not being designed for it, but the middle drive and FD don't have that issue. I am however considering trying and semi-synth later in the summer just to see how it goes. If the clutch slips I'll just switch back to dino oil. I figure if it don't, I'll just be lowering wear in the engine which would be good, but I don't want to do so at the cost of a slipping clutch.

[Bonz]

Thanks for the info Cy.

FWIW, seems to me clutch material/friction plates, etc would be similar even today compared to what was used back in the day on the XS, and synthetic oil in the crankcase wouldn't be an issue for slip anymore than dino oil. Obviously, the caveat is a synthetic oil that isn't energy conserving (w/friction modifiers) just as you wouldn't use an energy conserving dino oil.

I been thinking about running a synthetic oil of one kind or another, appropriate for motorcycles and the wet clutch, and would be curious if some guys have gone to synthetic in the engine and had clutch issues, assuming it was a proper synthetic oil to begin with.

Is you comment about the clutch slipping based on experience, or something you've heard as a pattern? You are the first person I've heard mention that, so thought I'd follow up.

[3Phase]

I didn't check my pinion nut with an inch pound torque wrench though. I just tightened up the nut up to 90 ft/lbs...... reckon it will be ok?

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??


Type I final drives use shims to set the pinion bearing preload with a specific torque value on the pinion nut. They can be somewhat time consuming to set up and may require an assortment of precision-ground shims but the Type I is a little more tolerant of over and under torque on the pinion nut.


Type II final drives have a Phillips screw next to the input coupler on the front of the pinion housing to the hold the pinion assembly in place; very easy to spot when you look at the final drive and it requires no precision-ground shims to set the pinion bearing preload.

Type II final drives use a crush washer instead of the Type I shims to set the pinion bearing preload. There is a torque range given for the pinion nut along with the in/lb specification for the pinion bearing preload.

As you tighten the pinion nut the crush washer is crushed and you check the bearing preload as you go. The correct bearing preload should be established somewhere between the lower and upper torque limits or something is wrong and you need to find out what it is before you stuff the drive in your bike and go merrily barreling down the highway.

If you overtorque the pinion nut you will crush the crush washer and you may damage the pinion bearings and races. The crush washer is still available from Yamaha but I'm not sure about the pinion bearings and races.

If you overtorque the pinion nut and then back it off to get the correct pinion bearing preload the crush washer will not have retained its shape like a Type I shim and it will not magically expand and un-crush itself. At best you will have to get a new crush washer and try again. If you really ham-handed it like, for example, spinning the nut down with a big ol' socket on a 1/2" impact air gun, you may have to replace the pinion bearings and races, too. At that point it's much easier and a lot cheaper to just get another final drive and try not to do that again.


So, do you have a Type I or a Type II 750 final drive and how did you arrive at 90 ft/lbs of torque on the pinion nut?

[skids]

I didn't know the procedures when I installed mine (typeII) and I guess I lucked out because I have put on probably 4000 miles without an issue. With the final drive laying on the floor of the garage, it was all I could do to hold the radial gear from turning while getting the nut "good&tite".

[Codger]

25K and counting.

I have over 25K on my conversion with no problems. I have taken many long haul- 2K- trips and will testify that cruising at 80 mph at 4500 rpms is a boon to long distance touring. I will never with a capital "N" go back to stock and as I am now up in years, 1/4 mile ETs are not of great importance either. I guess its just a matter of priorities- but for me this conversion gets an A+.

[DGXSER]

On my first 750 FD, I pulled my rear wheel, mounted the 750FD on the gears, and put a piece of wood in the wheel to keep the FD from turning. Took my torque wrench and tried like he!! to apply the torque listed. I never got over 70 ft-lbs. But even at that, I could not turn the FD with that torque applied to the nut. So I backed it off until I could turn the FD properly. Installed it like that, and rode over 5k miles before me and Thunderstruck met a guardrail we did not like. Never had a lick of trouble out of that FD.