New project: XS1100 endurance racer

[Yamanatic]

Lots to look through, and sorry if I missed this bit of info if already mentioned:

XS1100's have an inherent (and dangerous) weak spot in the transmission. 5th gear runs on a bushing rather than a roller bearing, and has been known to weld itself to the shaft. This happened to me during an endurance race; one slight burble, and less than a second later the gearbox locked solid. I was WFO showing about 140mph on the speedo when this happened, and nothing to do but ride (or crash) it out. Pulling in the clutch does nothing as the gearbox is coupled directly to the rear wheel.

I had no idea it was the gearbox and not the motor, and the rear wheel started to hop about the same time I grabbed the clutch expecting to just coast to a stop. The hopping just kept getting worse and started throwing the bike all over the track. I had not fallen down yet, and decided at this time to just ride it out instead of grabbing front brake and having the back end pass the front.

I was fortunate to be on the widest part of the track, and managed to not hit any barriers while skidding to a stop. It was sort of like throwing a steel bar through the back wheel at 140; not recommended. I was fortunate to have this happen on a straightaway, and everything began in a straight line. A corner or crown on the track would have earned me an instant trip to the hospital. Catastrophic failures at these speeds are enough to make one rethink racing altogether.

The engine was trashed as the cases fractured, the trans shaft twisted about 1/4 turn, and teeth were knocked off several gears. Unfortunately 5th gear did not shatter - that's one tough gear. I did run out of track at the end of the slide, and was let down gently somewhere below 50mph; whew...

After doing some post-failure investigating, I found that other XS11 owners had similar failures with mixed results. at least 2 instances were reported by Autobahn riders, and several racers had partial failures of the bushing. I retired my 11 from track racing, and rebuilt it with the Turbo for racing of the 1/4 mile variety. The avatar is that particular bike today; I have owned it 31 years now and it still reminds me of the ride of my life everytime I see numbers in the 130+ range. BTW, it has a needle bearing supporting 5th gear now!

[WMarshy]

....BTW, it has a needle bearing supporting 5th gear now!

Any chance you remember what the bearing stock number is? Did you have to do any machining to get it in there?

[Yamanatic]

I don't remember the bearing number, as it was about 28 years ago I did the fix. The modern bearing supply houses can come up with most anything from their 'stock.' I used the transmission shaft diameter as the crucial measurement, and had the gear I.D. machined to remove the brass bushing to tolerance fit the new outer race as it was necessary (for my approach) to locate the cage. The bearing looked like a miniature version of the R1 swingarm needle brg, with only an outer race and no inner.

The bearing was very economical, and machining charges were in the 1/2 hour range for labor. There was no need to re-harden the gear or shaft as no heat was used in the process. The big cost was buying another engine to bolt my slightly tricked-up top end to :-0 You may have a better way of engineering a fix; what I did just seemed to be the path of least resistance. I have logged about 20,000 miles of abuse since the fix (all with the turbo installed), and have not had it apart since buttoning it up way back then.

[Mathh]

Interesting to hear and I will surely have a look at it as soon as the engine comes apart (still on the "to do" list) but I have to be honest: I have been thrashing XS1100's since 1978 and I have never encountered this problem, I haven't even heard of the problem, ever. My first XS did approx 85000 miles within one year : most of it on the autobahn wringing its neck at absolute top speed, my second XS did only a bit less miles within two years but also at very high speeds. My turbo has been thrashed hard for approx 120.000 miles and shows almost no wear. The factory endurance kit, as used in the Dior XS, used the stock gearbox as did Mel Pitman with his Aussie endurance racers and my friend Baloo with the yellow endurance racer (the only engine he blew up was due to a broken hyvo chain).
But I am never too old to learn, so I'll do some asking around on the Euro forums.
Anyone on this forum heard of this problem?

[Yamanatic]

Hey mathh,

I was looking through your photo's and text, amd know you are not the occasional Sunday racer, that is why I brought the issue up as mine was slightly turned up from stock specs too, excluding your hand built chassis, 21st century technology and more generous budget (I was just a lowly mechanic at a YamaDealer when doing the SE region). Much of my feedback on the gearbox came from Bud Parker (the factory rep at the time), and since there was no internet, correspondence was by mail and phone.

It is amazing how much more interest and participation there is in the road racing community outside the USA; most of the dedicated knee-draggers, in our age group especially, are either from European countries or Australia; Belgium & Ireland seem to stand out in the community. If ever I were to relocate...

Anyway, mine broke coming off the tri-oval at Daytona during the Paul Revere 250 night endurance race on lap 56, about 100 yards past the infield entry. I remember thinking: "That burble didn't feel like it's out of ga...," and that was when the excitement began. It took all the way to the entrance to turn one to get stopped, and luckily directional inertia won. Daytona eats machinery, as you probably know all to well; if it's gonna blow, that's the track that will do (did) it, and for the second time.

Now I got one of these:

Archaic, but THAT is a gearbox for leanin' on. All roller and needle bearing with a dedicated pressure fed oil supply, and gear teeth the size of bullets. Digging around in there for a while can make one wonder about production bike engineering.

Keep up the good work, and when you get to the motor I am sure the same attention to detail will provide you with an extremely reliable machine. From the primary chain up, there is no stronger 4-banger outside of an automotive chassis. I particularly like the power delivery easing that much bike around turns; it is predictable and forgiving. Good luck!

Cheers,
Warren

[WMarshy]

Thought you might like this bike...

http://www.motorcyclespecs.co.za/mod...cafe_racer.htm

[dixiethedog]

I joined the forum after spotting this bike some how by accident! The build looks absolutely fantastic and i cant wait to see more. Keep up the good work.

I could probably write a thousand words saying how great the bike looks and complimenting your skills,but instead i'll write one word that says it all for me,and that word is;
WOW!

[Shacknasty]

Now I want to know how it all turned out. Is the bike finished? Did Mathh ever race it? Did the fifth gear bushing rear it's ugly little head at 140 mph?

[Mathh]

19 MONTHS AGO? it sure feels like a couple of months ago. The bike is still standing there as shown in the last pics, a bit less air in the tires..., but I see it 2 or 3 times per week, and I am sick of having no time to work on it. Well thank you guys for remembering me there is still work to do . I got a new job last year as a logistics manager and from that moment on I have had no time left whatsoever. Last year I made all the arrangements to do the ally bodywork myself but that obviously is not working as planned and now I am on the lookout for someone to help me with that. But these professionals are scarce (and expensive) aren't they? heheheh.
And that fifth gear? I did some research on most of the euro forums but all of them say it is very unlikely. When in 5th the gear has the same speed as the shaft it is on so why put in a needle / ball bearing?

@ Yamanatic: let me know if our thinking is wrong, still have to take the engine out

i really hope to post some good news soon ...

[Jocke-otra]

Wow,Wow,Wow......

No more to say...Hello from Sweden..god luck with rest of the bike...regards Jocke

[Bad Kaw]

Well, let's hope that your career gets the heck out of the way of your passion, so that viewing geeks like me can get more stimuli from your antics!
But seriosly, great work and I hope you find time to drive on.
-KR

[Mathh]

Well, let's hope that your career gets the heck out of the way of your passion, so that viewing geeks like me can get more stimuli from your antics! But seriosly, great work and I hope you find time to drive on.-KR

Looks like your cristal ball is working okay... naaah i did not lose my job. I asked my friend who built the frame if he was willing to help me out because i want to ride the damn thing. So, here's a new start..:
changed the long chain adjuster with a shorter and square one, works better, also a new bottom shock mount is now in place..



back in the frame, added some bobbins to the swingarm at the front of the adjusters (barely visible in the picture below..see the allycoloured circle)



we're discussing the new tank but engine mount and ignition cover have been welded in the meantime

[Mathh]

Today first metalwork started. 2mm thick aluminum. The lower piece will be part of the fueltank as well. Should look a bit like sidecovers. I skipped the idea of a monocoque fuel tank / seat combo. Seat will be bolted on top of the lower part of the fuel tank. That way I can change the looks more easily, just bolt on a different style of seat.. and make sure it will be stable enough to hold my weight..






and already one of the sides added...



last side part added for the day ..

[Mathh]

Still going strong ... bit more welds sides and bottom plate pulled more straight so they look more like the kawasaki tank..



Tank off to add the "grabbing hole" on the front. There will be another one at the back as well..



Inside and nose piece of the bottom..



piece of cardboard to get to the final form...



And the seat added .. Starting to look really good..

[Mathh]

Pictures are for trying the sides of the lower tank portion.. and of course the radius for behind the carbs ..



Next:
As Q and his Solidworks are no longer available I made up a drawing from the bottom of the tank, just to visualise things better.. excuse the dutch language...

Seat is still tilted backwards, that must still change. Top of tank and seat must be in one line..
Here a view from below. Bottom of the upper tank installed, not yet opened up. Small tunnel (invisible now) for middle of valve cover and throttle cable ..