750 FD Questions

[dbeardslee]

Anybody know if it's necessary to remove the bearing housing to plug the spooge holes on the 750 FD, or do you just have to plug them on the gear coupling? Reason I ask is the coupling popped right out, but the housing looks like it's going to be a booger. I've checked the tech tips and just can't seem to find the answer.

Also, I noticed in one thread that someone mentioned plugging the holes with epoxy rather than RTV. Seems like a longer lasting solution than RTV, assuming it works. Any thoughts?

[John]

When you say bearing housing, do you mean the pinion gear and bearing? That does not need to come out, but now that it is out, you need to remove the nut, and washer that holds the pinion to the gear, and clean and fill the holes, and lay a bead of silicone under the large washer, and retighten to a torque of 'guddentite', then reassemble the pinon to the final drive, and make sure you reuse the pinon shims if it had any in there. That is what sets the preload on the bearing. I don't know what the torque is for the pinion nut but I'm guessing it would be about 50 ft lbs, same as some of the nuts on the trans shafts.

[dbeardslee]

John - Thanks for the reply. I looked up the parts for the 750 FD on the fiche and used the 'yamaha' terms for the parts. The thing they call the bearing housing is the flange-thing with four holes in it that mates-up with the shaft housing.

I removed the pinion nut first, and was then able to remove the gear coupling with my fingers. So, if I'm understanding you right, all I have to do is seal-up the gear coupling and put it back on - right?

[John]

That is correct. I have done the swap on my bike using an 850 FD, and the gear housing is attached to the FD, so it won't come apart like yous has. I also have a 750 FD all modded up, and it came apart also, but the texture of the casting is quite rough, so I didn't use it on any thing, but it will be used on my bagger soon.

[dbeardslee]

Cool. Thanks John.

[dbeardslee]

John - I've got a couple more questions for you if your up for it. I checked with TC on the copper drive shaft spacer to see if any wear was noticeable on the copper. He said you be da man to ask. Sooooo, does the copper spacer perform adequately?

Also, the tech tips said the pinion nut torque (maximan says in the tip 75-105 foot-pounds) and the pinion pre-load are crucial. I've been all over the fiche trying to find a reference to the pre-load adjuster and came up with a goose-egg. Is the little philips head screw on the end of the bearing housing the pre-load adjuster? I don't see anything else there to adjust, but before I start turning screws I thought I would check.

[John]

The small phillips head screw holds the bearing housing to the FD. It is what keeps it from coming out. When mine came apart, it was when I was using 120 psi of air to blow out the solvent that was still in the FD, after soaking it in a parts washer. It just blew the pinion right out of the FD, and scared the hell out of me.
The shims between the housing and the FD are what determines the clearence from the pinion to the ring gear, and if they are not disturbed, then the clearence should not change when you tighten the pinion nut up. If maximan says the torque should be tehn believe it. That sounds like a lot though. I just zapped mine back together with my impact gun.
As far as the copper spacer goes, it seems to holding up just fine. I haven't had any reason to pull the driveshaft to check the spacer, so at best, it's just a ques, but I have not had any problems with the conversion. I love it.

[dbeardslee]

John - I appreciate the info. Unfortunately my conversion has been put on hold until I can find another u-joint. I just couldn't get the drive shaft to go into the u-joint yoke. Finally followed XSChop's advice, and took the swing arm off. Between me beating on the shaft with a hammer, and whatever the PO did to it, the end is ate up.

If I did the conversion I would only have had about 1/4" of good spline engaged, and that looked like a formula for a spline failure. Dremeled it back into shape, and put the old FD back on. Got an idea where I can get another u-joint - PJ are you listening? What the hey, this stuff's always easier the second time around anyway.

I'm probably going to back burner this mod 'till after I paint her. Your significant other is waiting for a paint report and I wouldn't want to disappoint her. Bye the way, have I mentioned you are one lucky man. All those bikes plus a wrench-turnin', bike paintin', sculpture creatin', joke tellin' biker babe. You must have done something REALLY good in a previous life

Thanks again.

DB

[John]

I have a spare U joint sitting in a box if you're interested. PM me and we can go over the details.

[TupperJ]

Originally posted by dbeardslee
Between me beating on the shaft with a hammer, and whatever the PO did to it, the end is ate up.

Got an idea where I can get another u-joint - PJ are you listening?

DB

Doug,

Still tuned in.

Bummer on the yoke. Come on out to the boneyard, I'm sure there's one out here you can have.

Paul

[tarzan]

Hey can someone tell me what the OD and ID are for the spacer you guys used in your F/D.I just bought a final drive on ebay and would like to turn a bushing before it gets here.It looks like according to the thread in the mod section the bushing needs to be 16mm long.Also I think I can round up a piece of oilite bronze.Would that work better or does that bushing even need lubed ?

[bikerphil]

bronze spacer

ID 29/32" mabye just a shade smaller.
OD 1"
You can buy one of these spacers (bronze bushing) at an Ace Hardware. Bushing does not need to be lubed.

[tarzan]

Thats what I needed,Thanks bikerphil

[bikerphil]

re-checked that

Hey Tarzan, I rechecked the ID, it's 3/4".

[dbeardslee]

After action report

I finally got around to picking up a different u-joint yesterday. Dragged it back to the man cave and installed it so I thought I would resurrect this thread for results and some observations. I've only put 22 miles on this setup but I did notice some things.

First, from the launch she's very smooth, and the way I ride, it actually takes off faster on a 'normal/rational' start than it did with the stock rear end. The reason seems simple enough - with taller overall gear ratio at a given rpm your traveling at a higher rate of speed - duh. It's a little unexpected at first, but soon becomes second nature. I'm going to have to learn how to go around a corner all over again as well. I usually like to go into corners slightly on the throttle to maintain the arc of the turn. Throttle response is different enough with the new FD that tight corners feel totally different. On the highway it's a dream - rpms are way down, and she's just a lot smoother. I gassed up right before I took off, and my mileage on my last pre-mod tank was 30mpg. Although it's too early to say, I believe my mileage is up. I watch the fuel gauge like a hawk, and the needle is definitely dropping more slowly than it did before. How much more remains to be seen, but I'm cautiously optimistic.

If I was planning to do this mod, there are definitely some things I would do first. As you will be running at a lower rpm at any given speed I would first make sure that the target machine runs strong across the entire rpm range - particularly at the lower end of the spectrum. If you're having problems fouling plugs or running rough at low rpms, fix that before you install the FD - it'll only amplify those problems.

Although there are those who have done this mod with the swing arm in place, I would plan on removing it as well as the universal joing for this procedure. It's so much easier to fit the u-joint to the drive shaft with the swing arm removed, and in doing it this way you may avoid my unfortunate experience with your u-joint. I think it's probably quicker than using the brail method of lining up the splines as you can spend a long time and waste a lot of good profanity doing it that way. It's very easy, and it also affords the opportunity to repack the swing-arm bearings - one of the more neglected maintenance items I'm sure. Make sure you crack the bolts on the u-joint first. If you remove the rear wheel, when you apply torque to those bolts it's only going to spin the drive shaft. With the wheel in place you can use a piece of 2 X 4, a broom handle, an old tree branch or the like to lever against the rear wheel and thus imobilize the u-joint.

While you've got the rear wheel off, it's an opportune time to repack the rear wheel bearings as well. Those big bearings are getting hard to find, but grease is easy to find. If any parts are deserving of a little extra TLC it's the ones that are made out of unobtanium.

Grease and tires don't mix well, and there's a pretty good amount of grease involved in these processes. Take a rag and some degreaser to your rear tire before getting it out on the road. It's hard to see on a tire, and you don't want the road finding it for you. I found some on mine - it was right on the outer contact patch area in an excellent place to make it break traction in a hard cornering situation - you know, right when you don't want it too.

Make a thorough final inspection before getting it out on the road. I had one little oh s**t moment when I hit a bump and heard a big clunk in the rear. I'm pretty sure I left a brown smear on the seat . I pulled over and started checking things - turned out in my haste to get it on the road I had neglected to reinstall the bolts that allow the rear fender to be lifted - I always take them out, move the fender up, and then put them back in so I know where they are when it comes time to put 'em back. My rear fender was flopping around and making the noise - what a relief!

And lastly, time your mechanical activities to complete when the sun is shiny, or it's at least dry outside. Right now it's raining in Cincinnati, and it's KILLING me not being able to put more miles on this mod. It's that good .