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Likes to race old junk.
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Discussion Starter #1
Hi everyone,
This my first post. I was slacking off and surfing the net hoping to find race parts for early GSXR's and ended up on this site and then was surprised to see a recent thread on one of my race bikes. I just enjoyed my 8th year competing at the Bonneville Salt Flats, I've had some success with very large displacement Hayabusa's. I still own my first race bike, a 1986 GSXR 1100 built as a period endurance racer.

One of my mentors, Larry Forstall built my twin engine GSXR back in the early 90's. Larry built it to run in the "naked" classes without any bodywork. Other than a couple of shake down passes which were aborted due to vision problems and salt conditions, the bike has never run. The Double sat for over a decade in Pennsylvania. I met Larry in 2002, the year that I got inducted into the Bonneville 200 MPH Club and he mentioned having a twin engine GSXR in storage. I was after Larry for several years to either sell it to me or let me fix it up and race it. Bonneville has such a rich history of multi-engine vehicles, I thought the Double was very cool. I was teased with pictures at first but Larry finally agreed to sell it to me and I had it shipped up to Alberta, Canada. I will always run it as a "Beairsto & Forstall" entry. Larry is an innovator and I'm proud to own a piece of his work.

The Double uses a pair of 1986 GSXR 1100 engines, they are now 1255cc with Cosworth pistons, ported heads, Carrillo rods, Falicon cranks, Megacycle cams, 40mm flat slide Mikuni's, all the good stuff that was available at the time. Older technology for sure but horsepower is horsepower. The engines are coupled together, both transmissions are engaged.

I work overseas in the middle east and Africa, I'm not home much and it was hard trying to get 3 other race bikes ready for Bonneville. As anyone who has run at Bonneville knows, corrosion is a bitch. It doesn't seem to matter how much you clean up afterwards, it ruins everything. Having sat for so long, the bike needed some attention. I also wanted to be able to run the bike with bodywork and decided that an early GSXR competition fairing was the right choice. We replaced the wiring harness, spark plug wires, cleaned the carbs and got the front engine running fairly quickly. The rear engine gave us a little more grief but we sorted through the electrical gremlins. A seized rear custom clutch slave cylinder almost kept the bike at home, we fixed that the night before we left.

I had never driven the bike until I let the clutch out for the first time on the salt. Its very stable at speed but it is a bit of a stretch even laid out over it and the gear shift pattern is backwards.
The front engine is started using a battery cart, with the bike on a stand, I shift into 1st gear, rev it up a little and drop the clutch. The rear engine fires up and the bike gets alot of attention. I put it back into neutral, the stand is removed and I wait for the starter to give me the ok to run on the course.

I did a couple of passes on the short course to get familiar with the bike but we soon discovered a weak link in the engine's coupler. I knew with the weak idler gear that I would only be able to make a few runs. My top speed was 203mph @ only 7000rpm, the bike has alot of potential in it. I like it because its different, my Hayabusa disappears in a sea of other 'Busas at Bonneville. On my last run, we actually broke the coupler's idler gear and the loose chain caused a bit of damage but nothing that can't be repaired. There's nothing like running 200 mph and hearing bad crunchy noises coming from the coupler.

I hope to be able to run it again this year at Bonneville or El Mirage, work permitting. The bike is in a shop right now getting the coupler modified. I also need to improve the rear suspension and add some ballast for traction. It just spins the tire hopelessly at anything over 3/4 throttle. Over the winter I'd like to throw some more power at it and upgrade the 1255's, its a shame they stopped making the big blocks. We are entertaining the idea of adding fuel injection as well.

Well I should get back to work.

-Scott
 

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Save water, ride an oiler
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341 Posts
Hello and welcome, that is a very cool bike. Thanks for dropping by and letting us know about it. I do however need pictures of your 86 1100 as well.
 

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The other OG
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6,334 Posts
thanks for the info i'm the triumph guy who remarked in the thread on your bike previously , teething can be a bitch -take a leaf out of the worlds fastest indian movie and test it on utah public roads - or bring it to the aussie salt flats and blow some aussies off , well done canuck from oz
 

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Premium Member
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3,338 Posts
Welcome Scott :cheers

Thanks for charing, that's an incredible looking machine, a co-worker and i where wondering how does the drive system of both motors turn the rear wheel?
Do you have some pics of the left side of the bike?
 

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Premium Member
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7,715 Posts
Very cool.. How in the hell do you "mate" the two engines together? I just can't picture it in my head..
 

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Likes to race old junk.
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1,606 Posts
Discussion Starter #7
All,
The 2 coupler output shafts are chained together and splined to the factory output shafts . I believe a stock counter sprocket is a 14 tooth, these are both 17 tooth. I have rear sprockets from 32 teeth to 40 teeth, so its got lots of gearing. The output shafts are supported by outboard bearings in a heavy duty plate. This coupler was $5 grand in 1990 money. There are alot of nice pieces through out the bike, lots of money spent at a machine shop, for example the shifter has a needle bearing. This coupler is a simple way of doing things but its hard to synchronize the 2 engines. There is no charging system, again the front engine is started using an external battery cart and the rear engine is "bump" started off the front engine. The fuel pump, 2 ignitions and 2 Trail Tech computers are run total loss from a battery near the swing arm.

I don't have any pictures on my work lap top of my old '86 1100. It just sits in my collection. I drive it for a year and then lay it up for a few years. I just love looking at it, it's like an old Corvette, a new one's faster but the old one is just as cool. It was in a museum for a couple years a while back, it was nice to let someone else dust it off. I'll probably put it back on the street again next year, its got lots of grunt. Its been road raced and drag raced over its career. I bought it in '98 and restored it. I took it to Bonneville in 2000 and I've been addicted ever since.

-Scott
 

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Likes to race old junk.
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1,606 Posts
Discussion Starter #8
Yeah its a bit of a stretch to reach the clip ons. I'm 5'11", quite a bit taller than Haley, our umbrella girl. She's the daughter of one of my crew, Soren. How many 15 year old girls want to hang out with a group of middle aged guys thrashing on race bikes for a week?
We put the foam padding on because you would actually bruise your chest from laying on the frame for even a few seconds. The chassis was engineered by Precision Chassis. Regarding these altered frame, special construction bikes, the SCTA requires that steering be limited to only 15 degrees each side. The steering stops are adjustable, its no fun trying to push it around to get it on the lift or in the trailer.
The fuel tank is in the tail section, a fuel pump feeds the 2 banks of carbs.
The hydraulic clutch master cylinder operates both clutch slave cylinders.
There are 4 oil coolers, they limit how much we'll be able to enclose the bike. The rear brake is just used to get it off the trailer, its got lots of engine braking.
-Scott
 

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Premium Member
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4,680 Posts
Oh yeah!
I saw your bike earlier in another thread here... It's just deadly!

It sure would be great to hear that bike do its thing. Maybe the next time you run on the flats you can get some video. I'd just like to hear what two 1255's sound like in tandem :biggrin

Welcome aboard!
 

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Pretty insane machine if you ask me. My buddy has set a land speed record for the the fastest stock Truimph. It did 177 mph on a stock motor 995i. He added a turbo Him and owner Matt @ southbay Truimph was on the cover of Cycle World. I remember that bike wheeling at 100 mph on the Thomas bridge in San Pedro. Good luck with more runs on the bike. Thanks for pictures and write up. Never seen double runner before.
 

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Blithering Idiot
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fucking awesome :punk
 

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"How many 15 year old girls want to hang out with a group of middle aged guys thrashing on race bikes for a week?"

Not any of the ones I've met but she sounds like my kinda women! and my age aswell! Prolly knows more then I do about bikes tho haha.

Very nice bike. I agree with the others, lets see a vid of this thing!
 

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Premium Member
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An astonishing machine. See what you mean about that idler wheel design, it looks optimistic. Also the split-link in that chain :)
Yeah, I was thinking about that this morning..... I would have thought a gear driven setup immersed in gear oil would be a better solution.
 

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Yeah its a bit of a stretch to reach the clip ons. I'm 5'11", quite a bit taller than Haley, our umbrella girl. She's the daughter of one of my crew, Soren. How many 15 year old girls want to hang out with a group of middle aged guys thrashing on race bikes for a week?
We put the foam padding on because you would actually bruise your chest from laying on the frame for even a few seconds. The chassis was engineered by Precision Chassis. Regarding these altered frame, special construction bikes, the SCTA requires that steering be limited to only 15 degrees each side. The steering stops are adjustable, its no fun trying to push it around to get it on the lift or in the trailer.
The fuel tank is in the tail section, a fuel pump feeds the 2 banks of carbs.
The hydraulic clutch master cylinder operates both clutch slave cylinders.
There are 4 oil coolers, they limit how much we'll be able to enclose the bike. The rear brake is just used to get it off the trailer, its got lots of engine braking.
-Scott
looks kinda uncomfortable but definantly a cool piece of machinery
 

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Likes to race old junk.
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1,606 Posts
Discussion Starter #18
All,
The coupler's idler gear was made out of aluminum, 12 tooth, it appeared to be a custom piece, I broke it on my last run. I'm going to use a steel one next, it will be pressed onto the bearing. After my 2nd pass, we noticed the idler gear was getting loose on its bearing, we tried staking it and using green loctite, of course, it only continued to get worse. Nothing ventured, nothing gained. The original coupler chain was just a regular 530, I "welded" it together on my 2nd pass as well, we ended up using some 530 drag race chain off my 'Busa. The bike builder's plan was to just lube the hell out of the coupler chain before each pass. I'm going to install a chain oiler, an upper chain guide and use a 530 o-ring chain. I actually prefer a clip style master link vs. a rivet link, either way the side plate has to be pressed on, it isn't going anywhere. We'll try this set up first. An oil bath would be nice but it would require re-engineering the coupler plate, I think the chain oiler will work ok. Yeah, we spent lots of time in the pits drinking beer and pondering our options, we'd need 5 idler gears if we went to a gear drive set up, again lots of money and re-engineering.
Thanks for the positive comments. I'm working in Dubai right now, I can't wait to get back home to Canada and get back to work on the Double and our other projects.
-Scott
 

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Thanks for the update Scott.
That's definitely a cool ride!

I almost went to Dubai. A friend of mine was over there and I had an open invitation to stay any time. All I had to do was get there. Unfortunately her contract ended and with it my chance to hang in the Emirates for free.

Cheers,
Andrew
 

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Ah, it just looked under-engineered. I thought the weakness with the idler would be its rather flimsy adjustable mount, which looks like it'd flex under stress. I thought it would need a triangular carrier made of plate - two mounts at the bottom - with a tensioner adjustment slot on one mount.

I guess such a small idler is going to rev so fast and present a high load to small bearings. A bigger one would allow a larger spindle with larger bearings and use of an off the shelf output shaft sprocket. But maybe there isn't the offset to allow all that.
 
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