Variation of the 750/850 final drive mod

[dbeardslee]

Here is a great U-Joint tutorial thread:

How to Change/Lube Driveshaft U-Joint

That is a good tutorial - and I've already got all the tools CG used, with the exception of the little angled adapter. Shouldn't be too hard to make one, though.

I love it! Spicer made a fantasy video!

The thing that always gets me about that video is the way the grease sucks out of the u-joint when the caps are pulled off.

I always clean the groove for the clip real well, and hit it with a file. It's not so much of a problem on these type of u-joints where the groove is in the u-joint itself, but on the kind with the end clips 9 times out of 10 dinged up grooves are what cause the u-joint to be too tight.

[3Phase]

Thanks, Marko! Clark's tutorial is a good one but there's another thread with a second fabbed tool that keeps you from bending/deforming the yoke ears when you press out the caps. These little u-joints are simple, the ones you need hydraulics to lift with special jigs and precision gauges to position and mount aren't so much fun and they really hurt if you drop 'em on your toes.

I have to go to the doctor today, I was coughing so hard last night I passed out and woke up on the floor with no idea how I got there. Darned cough.

Doug, the grease starts to pull out but then it pops right back in and pulls whatever was at the entrance back in the lube gallery right along with it.

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[dbeardslee]

I have to go to the doctor today, I was coughing so hard last night I passed out and woke up on the floor with no idea how I got there. Darned cough.

I had a guy do that in my office once. I told him a joke, he started laughing, then coughing, then TIIIIIIM-BER! I thought I actually knocked him dead.

When you cough it causes your blood vessels to contract a bit, and sometimes that can cause the lights to go out. Hopefully it's nothing serious, but it will sure get your attention when it happens. DAMHIK

[3Phase]

I had a guy do that in my office once. I told him a joke, he started laughing, then coughing, then TIIIIIIM-BER! I thought I actually knocked him dead.

When you cough it causes your blood vessels to contract a bit, and sometimes that can cause the lights to go out. Hopefully it's nothing serious, but it will sure get your attention when it happens. DAMHIK

Laughing is the worst part of it! I'll be fine, then something or someone will make me laugh and it's like hyperventilating. Sheesh!

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[dbeardslee]

Laughing is the worst part of it! I'll be fine, then something or someone will make me laugh and it's like hyperventilating. Sheesh!

.

I've had bouts of passing out, and ever since if I feel myself getting light-headed I drop to one knee and put my head down and try to breath normally - in through my nose and out through my mouth. Haven't passed out since adopting this method. And I figure, even if the lights do go out, I don't have as far to fall.

[3Phase]

I've had bouts of passing out, and ever since if I feel myself getting light-headed I drop to one knee and put my head down and try to breath normally - in through my nose and out through my mouth. Haven't passed out since adopting this method. And I figure, even if the lights do go out, I don't have as far to fall.

The doc gave me a pulmonary treatment in her office, then prescribed an inhaler and some anitibiotics. So far, so good!

On a final note to restate and clarify the condition of the drive shaft when I discovered the yoke splines were worn. There were no bright spots or polished splines on the drive shaft. The drive shaft and the splined spacer were both in pristine condition.

At every rear tire change I painted the splines with Honda Moly60, then filled with high-temp moly bearing grease on both sets of splines for the u-joint yoke and input pinion.

All of the splines still had their coating of Moly60 but the yoke splines were tapered, stepped and wallowed. Again: after cleaning off the moly paste, the drive shaft splines only showed the normal contact pattern. If they had shown anything but normal contact the yoke would have been pulled a long, long, time and thousands of miles before it wore to the point that it did in the pictures I posted.

I believe there is a significant difference in the loading of the drive trains on the XS11 Standards and the drive trains on Specials and XJs. It has to be the difference between the 17" and the 16" rear wheel because everything else is the virtually identical and that has probably caused a lot of confusion and consternation.

Most of the people I've seen with the '750/'850 mod' have Specials along with one very vocal XJ. The only comparison I can make between the the two ratios is that it's similar to taking off in 2nd gear on a Standard. The same drive ratio change on a Special or XJ would be more like taking off in 2nd and 1/2 gear so there is a difference that could explain the wear on my '80G yoke and the lack of wear on the Specials and XJs.

I've been spending too much time online talking about wrenching and riding instead of actually wrenching so I can ride. I've shut everything off here on XS11 and I'll be putting my bike back together instead of other peoples' bikes on the Internet.

[CaptonZap]

I've been spending too much time online talking about wrenching and riding instead of actually wrenching so I can ride. I've shut everything off here on XS11 and I'll be putting my bike back together instead of other peoples' bikes on the Internet.

Aww, come on Scott. Your posts are funny, until you start taking all the other baboon's chatter seriously.
DON"T LEAVE US, PLEASE!

CZ

[Bonz]

Hey Scott, Don't go just yet. I feel I understand the overall gearing changes that occur with the FD swap, so a clarification please....

It is a given the tranny's are the same in Specials and Standards, and the stock FD is the same as well. Only difference is the 16" vs 17" tire.

If RPM at 60 mph in top gear is the same for a stock Standard and an FD modded Special, that would translate into basically identical rpm/gear combinations across the board, no?

I mean, the FD is the "equalizer" and with all else equal internal to the tranny's, then rpm should be basically the same in all gears/road speed situations. Am I not understanding the overall gearing concept like I think I am?

I felt that was the case when riding my G back to back with the SG, rpm was basically identical and feel to take off from a start was the same to my seat-of-the-pants.

-You are saying on an FD modded Standard that 1st gear is now what 2nd gear was with the stock FD Standard. I think that is the comparison you are making, which should be correct. Just clarifying as it wasn't clear in the way I read it.
-As well, a Special with an FD mod is like taking off in 2nd and 1/2 gear relative to the stock Special or relative to a stock Standard?

Just making sure I know what bike (std or special) is being used for reference in each case.

Still, back to the original question... Is the overall gearing not basically identical with an FD modded Special vs the stock Standard?

[dbeardslee]

A 16" rear tire with a 130/90X16 tire is going to be around 6.594 feet in circumference. A 17" rear tire with a 130/90X17 tire is going to be around 7.117 feet in circumference. So for every revolution of the rear tire a standard is going .523 feet farther than a special. So with the same final gear ratio, and at the same rpms the standard is going to be traveling faster. Or at the same speed in the same gear the standard will be running at lower rpms. To figure out the exact differences you'd have to know the gear ratios coming out of the middle drive, as well as the FD gear ratios for the 750/850 and the 1100.

[trbig]

So if your measurements are correct, that equates to an 8% difference. (6.594' x 1.08 = 7.12) 8% of 5,000rpm is a 400 rpm reduction... which falls between the stock and modded final drives.

[dbeardslee]

So if your measurements are correct, that equates to an 8% difference. 8% of 5,000rpm equals 400 rpm reduction... what I've been trying to say all along.

Never doubted you for a minute - but I did screw up the math. Here's how I get what should be the correct measurement.

A 130/90 tire has a section width of 130mm, and section height is 90% of section width, or 117mm. 117mm is 4.6 inches. So the radius of the 16" would be 8"+4.6"=12.46". 8.5"+4.6"=12.96". Using the formula for the circumference of a circle, C=2πr you get the following...

For the 16" - 2X3.14X12.46÷12=6.52 feet

For the 17" - 2X3.14X12.96÷12=6.7824 feet

for a difference of .2624 feet.

First time I did it I added an inch to the 16" radius when I should have only added 1/2".

I still think you have to take all the gear ratios into account to do the figuring for engine rpms, since an 8% reduction in the rear wheel rpms isn't going to necessarily equate to an 8% reduction in engine rpms, unless there's a 1:1 ratio between engine rpms and rear wheel rpms. If there's a 2:1 ratio between engine rpm and rear wheel rpm then a 4% reduction in rear wheel rpm would yield an 8% reduction in engine rpm.

Or is it the other way around? This is starting to make my head hurt. Where's all the math majors when you need them?

But the easy way is to just look at the tachometer, and I agree with you about the 400 rpm difference at 5k rpms.

[dbeardslee]

And I screwed up the math again! 8+4.6 is 12.6, not 12.46. So it's 12.6 and 13.1 inches in radius for the 16 and 17 inch wheels respectively.

16 = 2X3.14X12.6÷12=6.594 feet

17 = 2X3.14X13.1÷12=6.856 feet

difference = 0.262 feet

[Bonz]

Anyway, I love the FD swap! Greatest mod ever for this bike, especially the Special, IMO.

[red bandit]

Starting out in 1st gear with a standard with 750/850 FD is NOT like starting out in 2nd with a standard with stock FD. There isn't THAT much difference.

[dbeardslee]

It's amazing how fast you get used to the difference in the gearing. I've got two standards sitting out in the mancave right now - one with the 750 FD and one with the stock FD. Just for grins I think I'll take the stocker out later and try a start from 2nd gear, just to see what it feels like. Might do a little rpm comparison too.