Variation of the 750/850 final drive mod

[trbig]

That's great! I'm glad y'all have gotten the mileage you have but you make it seem like it's some kind of onerous, time-wasting security blanket.

It is, but some people need that security blanket. Nobody has ever wiped the splines in the yolk from this mod just using the collar. Ever. I realize you don't care about how many bikes I've crashed or parts I've tore up, but I was making a point that I don't think anyone has ridden their bike any harder than I have, for the number of miles I have on this mod. I could be wrong about that, but sorry if you personally feel that information is inconsequential. I do feel you're trying to "fix something that ain't broke", but to each his own. I know this has been one of TC's concerns since the day this mod came out, so good of you to design something for those types. That being said, I also think people should have all the info on something and not have someone new coming on, seeing this post, thinking they HAVE to do this cutting/welding. I'm also glad you found someone to do the welding for $10. No professional welder I've met would even turn their welder on for that.

Now if we can just do something about the ones that say the 750/850 drive will be like starting their bike from stop in 5th gear....

[CaptonZap]

The u-joint yoke is cast iron, the splined barrel can be cast iron or steel.



Goosfraba....

Welders have to eat too. If you can't do it -- I cannot -- they're in the phone book and some of them advertise.




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If I only had nickel for every cast weld!!!

Actually, every yoke I've known is forged, cast being too brittle to take the loads imposed. The forging flash marks can be mistaken for casting flash, but the grain structure, or lack there of, is obvious.

CZ

[3Phase]

Good morning, Tod. Goosfraba.... I woke up again on the right side of the dirt again today and I just don't care but I have some time to kill before I can make noise without waking anyone up.

Cap, I sent you a sawed-off section of what I believed was a cast iron u-joint yoke, is it cast iron or forged iron? I couldn't tell you one way or the other but forged does make sense.

TWIMC: If it bothers you in the least possible way imaginable DO. NOT. DO. THIS. MOD. FULL. STOP.

The worst thing that can happen if you strip or split the u-joint yoke is that the engine cannot move the motorcycle and you'll have to replace the yoke. Unless it breaks in a hard corner, in the middle of an intersection as you take off or after you've stopped in the middle of some railroad tracks to look in both directions for alligators before cautiously crossing the tracks: big whoop. There really is nothing to worry about, it's not like the driveshaft can drop down and jam into a manhole or a pavement joint and polevault at one-hundred miles an hour.

Tod, I guarantee that I have not and I will not ever tell anyone that they have to do this mod. You're like a cuckoo in a clock and spring out every time I've mentioned Yamaha's driveshaft wobble spec or strengthening the u-joint yoke instead of using a copper/bronze spacer as if you invented the '750/'850 mod and have stock in bushing sales. What's up with that anyway? It's not the time because it doesn't take time, just a little planning and it can't be the money because no one here has any!

Oh, yeah, I got the yoke welded at the muffler shop so I'll be sure and tell him how unprofessional he is for you, I'm sure he'll immediately raise his rates -- thanks a lot, man!


Yamaha obviously needed a security blanket too because their engineers felt strongly enough about the u-joint assembly to change the yoke design from a one-piece casting to a two-piece cast iron/steel part. That meant real money for the redesign, the paperwork, the tooling and the extra weld. Think of all the money they could have saved if they'd asked you to design it for them!

While you're feeling invulnerable, go out and grind off all of that extra gusseting and the reinforcement welds on your XJ. You don't need it, it was a total waste of time and it's just a security blanket for insecure riders that constantly worry about breaking the frame. Yamaha could have saved some money on electric pencils too because only insecure worry-warts that need a whole entire pile of security blankets would have wasted all that time and effort to scribe final dimensions on precision-ground gearsets and slavishly follow meaningless torque values when all they really had to do was wipe stuff off and tighten stuff up until it was about right.

As for no one that's done the '750/'850 mod ever stripping a u-joint yoke, I love it when people 'speak' in absolutes. A sample size of -- I'll be totally generous here -- one-hundred people that have done the '750/'850 mod is insignificant when compared to the power of the for... sorry, my powered armor got stuck again, two or three or even twenty is less than completely meaningless.

I did a quick search for some sales numbers and found a site in Europe with European sales and registration:-

Official sales numbers of the XS 1100 in Europe between 1978 and 1988

They listed 19,057 bikes in Europe. Even the least significant digits in that figure are half of the total number of people on the entire planet that have done the '750/'850 mod. Now, how can we get the '750/'850 drive to work without feeling like you're taking off in 5th gear?

And so, hi-ho, hi-ho, it's off to get parts cleaner all over me again I go!

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[BA80]

Now, how can we get the '750/'850 drive to work without feeling like you're taking off in 5th gear?

And so, hi-ho, hi-ho, it's off to get parts cleaner all over me again I go!

.

No real significant difference there. First gear with the FD mod isn't even as hard to take off as second is with the stock FD.

People who have ridden my bike say they can't even really tell the difference.

[CaptonZap]

Cap, I sent you a sawed-off section of what I believed was a cast iron u-joint yoke, is it cast iron or forged iron? I couldn't tell you one way or the other but forged does make sense.

[
Oh, yeah, I got the yoke welded at the muffler shop so I'll be sure and tell him how unprofessional he is for you, I'm sure he'll immediately raise his rates -- thanks a lot, man!






And so, hi-ho, hi-ho, it's off to get parts cleaner all over me again I go!

.

It looked like you cut that with a chop saw, which left heat blued flash at the edges of the cut. Cast iron doesn't do that, since the carbon cells in the iron don't blue, and the iron sheds it's heat to the carbon, and doesn't usually get up to blue temperature. Also, the inter granular bonds which bond the iron and carbon will allow the iron particles to break off, thus no flashing fins. Oh, it also tends to gum up the blade, unless the blade is an easily friable one specifically meant for cast iron.
And, while I am not an expert in the interpretation of grinding sparks, I would guess that there was a good bit of nickel in it, from the looks of the grinding sparks when I ground the mating surface. It was not cast iron.

And some might say "Oh, then it was cast steel". With which I would agree, after closer examination of a yoke, and noticing that there were a few places which had no draft for the removal of the dies. If that is the case, then what we are worried about with the welding is a moot point, since cast steel welds about like regular rolled steel, which is rolled from cast steel, Uhmmm, forging is forcing hot metal into a new shape. Like sheet rolling mills. Now that is some forged sheet.
Also, I don't know of many muffler shops that use a TIG welder for day to day operations, but that is what it looks like, so it wasn't some shlock job welder. If the joint was V'ed, and it appears to have been, then what ever wire he was using has enough strength to hold it together forever, since the stresses on the weld are minor tensile, not shear. My 42 year old van with a 33 year old welded U-joint can attest to that.
Don't worry, be happy, and go back to bathing in parts cleaner.
Or, as we used to say, ZEP a dee do da, ZEP a dee aye, My oh my, we're gonna smell that all day.

CZ

[3Phase]

Lunch time

BA, I was -->.<-- that close to running my first (and only ) '79 Special with a '750 drive when I discovered the #3 cylinder had serious rust issues from being left outside for years in salt air. For some reason it hasn't put itself back together yet, either. Bad engine!

Cap'n, I used an angle grinder, of course. I cut it as slow as I could right at the 'flare' and made it longer than the spacer needed to be so you could make it all prettyful an' such before you welded it up.

If the yoke and the barrel are both steel then there's no problem but muffler-guy lied and extorted an extra five bucks out my pocket after saying he'd do the job for $5. You really should check out a modern muffler shop though, they have the technology!

Two guys were setting the jigs and supports for a titanium and stainless steel catback exhaust under a shiny-new Mustang they had up on the lift. They were using some kind of wire-fed welder with a gas bottle but I couldn't tell you what it was and there were a few more, different, rigs along the back wall of the shop that weren't being used.

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[CaptonZap]

Cap'n, I used an angle grinder, of course. I cut it as slow as I could right at the 'flare' and made it longer than the spacer needed to be so you could make it all prettyful an' such before you welded it up.

If the yoke and the barrel are both steel then there's no problem but muffler-guy lied and extorted an extra five bucks out my pocket after saying he'd do the job for $5. You really should check out a modern muffler shop though, they have the technology!

Two guys were setting the jigs and supports for a titanium and stainless steel catback exhaust under a shiny-new Mustang they had up on the lift. They were using some kind of wire-fed welder with a gas bottle but I couldn't tell you what it was and there were a few more, different, rigs along the back wall of the shop that weren't being used.

.

Thank you for your thoughtfulness, Scott. You truly are a gentleman, in spite of what everybody here says.

Obviously, with Ti and stainless exhaust systems in their repertoire, they would have a TIG. If they do it time and material, a base price around here, if they are already set up, is a buck a minute. Most welding shop have a half hour minimum, plus so much an inch/foot of weld. You got a bargin, you old cheap skate.
Equally as obvious is that it is not your fathers Midas store.

CZ

[TopCatGr58]

Hey guys,

Tryin' to "chill" here in the summer heat! Scott, I was wondering about why Yamaha would put a steel spline section on a cast iron section..as stated, would be some fancy welding there. It does make more sense for it to be all steel. As has been stated, the spacer alone seems to be quite adequate in both positioning the other end of the driveshaft against the final drive like it needs to be, and still allows enough engagement of the driveshaft splines with the u-joint yoke to be effective and not wear wrong.

My only concern was with regards to finding spare u-joints to cannibalize to be able to add the extended spline section. I like Zaps idea of welding a similar piece of steel pipe/tube onto the end of the OEM yoke to provide the same affect, but being WELDED to the end would be more stiff and help provide a little more stabilization of the driveshaft. Since it's been shown anecdotally that the amount of spline engagement with just the plain copper washer is adequate, then the use of a similar plain steel spacer that can be welded to the end would be equally adequate...and yet provide one doing this mod a little more piece of mind/security, whatever....with welding a steel spacer vs. just using the copper one....if they so desired...without the need to have to harvest a spline section from a donor yoke.

Of course, if one welds the spacer, then it's essentially not easily reversible, but someone who has a welder will also have a grinder, so that they can reverse it, but it's a little more work than just the copper spacer...YMMV!

T.C.

[Rasputin]

Hey guys,

As has been stated, the spacer alone seems to be quite adequate in both positioning the other end of the driveshaft against the final drive like it needs to be, and still allows enough engagement of the driveshaft splines with the u-joint yoke to be effective and not wear wrong.

Since it's been shown anecdotally that the amount of spline engagement with just the plain copper washer is adequate, then the use of a similar plain steel spacer that can be welded to the end would be equally adequate...and yet provide one doing this mod a little more piece of mind/security, whatever....with welding a steel spacer vs. just using the copper one....if they so desired...without the need to have to harvest a spline section from a donor yoke.

Of course, if one welds the spacer, then it's essentially not easily reversible, but someone who has a welder will also have a grinder, so that they can reverse it, but it's a little more work than just the copper spacer...YMMV!

T.C.

I like your thinking on this TC. Easily reversible is high on the list of things on ones mind when contemplating this idea. Of course, so is longevity once one decides they like the conversion, which makes the welding an option for sure. I just think that If I was really concerned I would go the copper spacer route and be happy. On a very high (racing) powered bike it may make a difference but to most riders it will not.
I kind of thought it best to mention it in the other thread, in order not to Hi-Jack it and it looks like we have a discussion going on here.

[CaptonZap]

Hey guys,

Tryin' to "chill" here in the summer heat! Scott, I was wondering about why Yamaha would put a steel spline section on a cast iron section..as stated, would be some fancy welding there. It does make more sense for it to be all steel. As has been stated, the spacer alone seems to be quite adequate in both positioning the other end of the driveshaft against the final drive like it needs to be, and still allows enough engagement of the driveshaft splines with the u-joint yoke to be effective and not wear wrong.

My only concern was with regards to finding spare u-joints to cannibalize to be able to add the extended spline section. I like Zaps idea of welding a similar piece of steel pipe/tube onto the end of the OEM yoke to provide the same affect, but being WELDED to the end would be more stiff and help provide a little more stabilization of the driveshaft. Since it's been shown anecdotally that the amount of spline engagement with just the plain copper washer is adequate, then the use of a similar plain steel spacer that can be welded to the end would be equally adequate...and yet provide one doing this mod a little more piece of mind/security, whatever....with welding a steel spacer vs. just using the copper one....if they so desired...without the need to have to harvest a spline section from a donor yoke.

Of course, if one welds the spacer, then it's essentially not easily reversible, but someone who has a welder will also have a grinder, so that they can reverse it, but it's a little more work than just the copper spacer...YMMV!

T.C.

Just in case someone decides to add a sleeve section, the OD of the splines on a 750 drive shaft is .875 inches. Wee don't need no steenking metric.
1/8 to 3/16 inch wall would work well for welding.

CZ

[3Phase]

A gentleman, eh? I'll have you know I've been called far worse but never by better!

A steel sleeve sounds good. I'm not inextricably wedded to hacking up u-joint yokes, that's how I did it for my bike. When I brought the parts in to have them welded they'd already been cleaned and degreased to remove the moly paste and I cut the v-groove between the pieces. I had both pieces stuck on the driveshaft like "yoke on a stick" so all the welder had to do was weld.

There is one problem that could happen with the lesser yoke: if you jump really hard on the throttle and the yoke does suddenly surrender the engine will bend valves or grenade before you can back off. Other than that I'm all for it, especially if it's someone else's bike and I don't have to fix it!

.

[CaptonZap]

There is one problem that could happen with the lesser yoke: if you jump really hard on the throttle and the yoke does suddenly surrender the engine will bend valves or grenade before you can back off. Other than that I'm all for it, especially if it's someone else's bike and I don't have to fix it!

.

Tsk, tsk, tsk, you never learn, do you?
Treat your machinery as you would be treated.
Easy on, easy off.
CZ

[3Phase]

Tsk, tsk, tsk, you never learn, do you?
Treat your machinery as you would be treated.
Easy on, easy off.
CZ

That's hard to do stoplight hopping or racing, err, demonstrating dynamic performance characteristics.

Engines used to bend or blow up all the time if someone missed a shift, snapped a chain, broke an axle or dropped a driveline, that's why hard and soft rev-limiters were invented. S.F.I. and NHRA require clutch/transmission shields along with a host of other safety equipment and the really high-performance bikes need certified safety equipment and a pre-race tech inspection or they don't go anywhere.

None of that is on a stock XS or XJ, especially the rev-limiter, so have fun and try not to hurt yourself.

.

[DiverRay]

None of that is on a stock XS or XJ, especially the rev-limiter, so have fun and try not to hurt yourself.

So you can get past the valve float?!?!? Oh, yeah, not in gear it will just go!

[3Phase]

So you can get past the valve float?!?!?

It's harder to do when everything's working and stays connected but if you're determined enough you can mess up the engine.

Oh, yeah, not in gear it will just go!

Bingo. Well, technically it's still in gear, it's just not connected to anything past the u-joint. Not my engine!

I was totally unsure and skeptical about the XS750 mod' at first so I kept the 'easily reversible' part for five years with the two 1/8" pins in the yoke. Tod and Greg are correct, the yoke is one tough cookie even when it's been de-rated with the spacer.

When I got done fooling around and decided I like the '750 and '850 Final Drives I got off the 'fence' and had the yoke welded before I broke something expensive. I have a couple more complete u-joint assemblies from the parts bikes if I want or need to go back to the stock '1100 Final Drive.

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