Modifying FDU

[dontwantapickle]

I got an idea, don't know if it will work...
maybe one of you guys does.

I'm thinking of upping the gearing on the race bike.
will the ring and pinion from a 1200 fit inside a 1100 final drive?

I have a couple of 1000 and 1100 fdu's to experiment with, but not a 1200 to actually take apart and see.
Anybody have one they might be willing to sell CHEAP?

Boy...
the things we bike guys come up with to occupy time when it's too cold to ride.

[Whiskerfish]

hmmm... most folks are trying to go the other way! To answer your question I do not know if it will work or recall any discussions about the possibility.

[ericheath]

If you could, (I don’t know) it would boost gearing top end 9% over an 1100. I’m guessing the final drive end of the pinion is different.

If you have a stock 17” rim now and went to an 18” you could pick up 5% maybe a little more with a taller profile tire.

If the 1200 couldn’t be used, an 80-81 17” rear rim would give best ratio due to the 1100 final drive ratio. 82-83 had 16” rims.

A few pics are not definitive, but perhaps checking pinion shaft part numbers might tell you that end of it.

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[dontwantapickle]

Exactly my thinking Eric.
Right now I have a 1980 1100 rear with a 17" rim.
1200's have 16" rims but a higher ratio.
2.83 vs. 3.09.
when it all said and done, they both work out pretty close to the same due to the difference in tire diameters.

Changing the gearing in the rear end is just an idea to keep the 17".
Or possibly modifying 1200 splines to fit a 1100 hub.

Adapting a larger rim to the 1100 hub is another possibility.
Problem with that is it's tricky to do it right and 19" tires with a high speed rating start getting expensive.

[ericheath]

1200’s have 15” rear rims, but a 1500 final drive can be adapted to the 1200 swing arm and uses a 16” rim, is also wider, uses a larger brake rotor, and is the same 2.83:1 ratio. Extra weight is probably not what you want.

I think the 17” 1100 is your best bet. One limiting factor is: I don’t think the 1100 swingarm will allow a 140 or 150 rear tire without modifying it some on the right side. If you could fit a 140 or 150 it would get closer to the overall ratio of the 1200.

The 1500 rim with a 170 would be great advantage as it’s almost 2” taller than the 17” 1100 rim.

I’m basing my numbers from RB Raving calculators. Tire size varies quite a bit from on manufacture to the next.

I also have a spread sheet of all the Goldwing differences over the years with much of this info. You probably have it?

[dontwantapickle]

When I started designing the bike,
I calculated that the early 1100 rear with the 17" was the tallest gearing I could get with what is easily available.

Then I shopped a bunch of tires to find the largest diameter with a high enough speed rating.
Turns out the Shinko 230 130/90/17 was the best option - so I went with that.
Wider tire width isn't better for LSR racing. If someone made a 125/100/17, I'd be all over it.

The Classic class that this goldwing runs in is against bikes with spokes and sprockets (Sportsters, KZ's, CB's, etc).
Changing gearing for those guys is a piece of cake.

[Whiskerfish]

I think that is part of what motivated the 1800 swingarm for Winston's LSR bike

[ericheath]

I would be leery of a 1200 swingarm for the speed you’re after. It is about 1/2” out of plane with the front wheel. That is how Honda built them. As long as everything is plumb, that’s not supposed to be an issue.

[dontwantapickle]

Yep Eric, again... we think alike.
that's why I was thinking of just the 1200 ring and pinyon and not the whole swingarm.

The gearing that I have now is pretty much ideal for the bike the way it is currently set up.
Improving the aerodynamics of the bike is going to put the gearing at its limits.
Improving engine performance and aero is going to need a taller gear ratio.

Trying to set a National AMA record is a once of year event.
The rest of the year it is about trying to make the machine perform optimally.

Bench racing, wrenching, calculating, tweaking, Re-tweaking is the bulk of land speed racing,
Riding the bike on the salt flats is the fun part.

[redglbx]

Great job Don ! I’ve always been fascinated by LSR, more so than drag racing. When my 76 was new Honda always claimed that they would cruise all day long at 132mph. So way back then we had a brand new, barely used bypass around South Bend and I was stupid to the possible legal issues along with being possibly hurt so I figured let’s find out if it’s true…

So my 76 would pull just over an indicated 130mph at redline in 4th gear but once shifted to 5th would slow to around an indicated 125, whatever that was actually. Very disappointing!

Anyway that run is what drove me to years of modding and the numerous dyno runs but I also got older and wiser (?) and never retried the top end run again. To much traffic & old age set in.

Anyway , I find it very cool what you are doing ! Will your bike pull redline in 5th gear ? What kind of speeds have you seen ? You are way more into this and understanding the piece’s than I ever did.

[dontwantapickle]

redglbx:
Land Speed Racing is just a hobby to me and the guys that I know. Theres no money in it, no prestige.
Just some bragging rights and the satisfaction of setting a personal goal and accomplishing it.

It's really not a very spectator friendly sport and the environment isn't remotely hospitable.
Truly, it's only the die hard motorheads and their supporters (tolerant spouses) that attend.

The events are really just a way of testing a tinkerers ability to tinker.

With todays technology (fuel injection, ECU's, etc) making the horsepower isn't the problem,
It's aerodynamics and traction.
The faster you go, the harder it is to go faster.

This here link explains the challenges of motorcycle lsr pretty well:
https://www.rbracing-rsr.com/aerohpcalc.html

My fastest time recorded on the salt is 133.160 mph. @ 6100 ft. density altitude
which works out to about a 18% decrease in available horsepower over sea level.

Not a rocketship compared to other bikes, but my old goldwing is faster than anyone in the class has ever gone.
Now that the bike has proven itself, the goal is to push it to the limit and see how fast it can really go.

[redglbx]

Yep Don, I looked into it pretty hard even thought about the group that uses runways, it just fascinates me and I’ve always had a thing for top speed, more so than drag racing. But between the money, family, work , etc, etc and the lack of any of the events being somewhat close and now with all the physical problems where just working on the bike has become a major problem .

The whole altitude thing is what drove my work to build horsepower in my bike and the things that I did to improve the power and the area under the curve. Anyway I do admire what you’ve done here and hope you have continued success !

[Sidecar Bob]

hmmm... most folks are trying to go the other way!

I don't understand why anyone would want lower gearing unless they were drag racing or pulling a sidecar. Every Japanese bike I've owned came from the factory seriously under geared. I blame it partly on the magazines publishing 1/4 mile times and the manufacturers trying to "improve" their numbers but on public roads with other traffic it doesn't make much difference.

In the real world there is a range of overall gear ratios that are acceptable depending on the end use. For around town cruising lower gearing is not really better but not terrible but if you spend much time on the highway you want higher.
With chain drive that can be fixed by installing a bigger rear sprocket (my '78 GS400 was much better with a 10% increase, even with the sidecar attached) but it is somewhat more difficult with shaft drive.
My '77 GL1000 was always a sidecar machine and its stock gearing seemed OK to me. When I put the 1000 engine in the '83 1100 it had significantly higher gearing. That was wonderful on 2 wheels, with lower RPM on the highway and significantly better fuel economy and I still rarely needed to gear down to pass. I'd have kept it like that forever except that it was too high after I added the sidecar (this is why I eventually changed to the 1100 engine).

In the CX/GL500/650 world a lot of people complain that the RPM is too high, particularly on the 500 models. You can raise the overall gearing on a CX/GL500 bu installing the clutch basket and the pinion that drives it with parts from a 650 and that was a pretty common mod for a while. One fellow did that and then went touring, pulling a trailer so I guess it worked pretty well.

BTW (speaking of Bonneville) World's Fastest Indian is on Tubi right now.

[redglbx]

Bob, I love that movie ! & the fact that it’s basically true is just something ! As far as the overall gearing thing goes, it gets driven into us that acceleration is the thing, that’s why it was so popular to put a 16” Lester on the early wings (me included) it does add about 400rpm at 60 but with 8500rpm to work with there’s still more speed available than is safe on public streets.

But once the LSR thing really got into my head I realized that it was not the thing to do,, overdrive tranny’s are the way to go really ! Now ask me what tire/wheeli have on the back of my 76 ! But getting that 400rpm back on my all stock LTD sure is relaxing going down the road.