Suzuki GSX-R Motorcycle Forums Gixxer.com banner
1 - 20 of 145 Posts

·
Likes to race old junk.
Joined
·
2,978 Posts
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
 

Attachments

·
Likes to race old junk.
Joined
·
2,978 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
 

Attachments

·
Likes to race old junk.
Joined
·
2,978 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
 

Attachments

·
Likes to race old junk.
Joined
·
2,978 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
 

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #22 ·
This is what we saw after the 2nd run. The chain was pretty much welded together, it must have taken alot of power to turn it. With the idler removed, you can see that there is a machined slot for it to rest in, which gives us adjustment travel. The idler mount with its bottom adjuster is quite solid. When the coupler's cover is mounted, a bolt goes from the cover and through the idler to the back of the coupler plate. So with all this, I 'd say it is triangulated. I think the design flaw was the aluminum sprocket and the lack of some sort of chain oiler. I've looked at Scott Oilers but picked up something off ebay for a go-kart, I'll modify it to dump a quart over 5 miles.
I appreciate your comments, its always good to have someone else's opinion on a solution.
I can't wait to ride the Double again. Its fun just starting it!
-Scott
 

Attachments

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #28 ·
I'm in the middle of a desert some where in sunny Saudi Arabia right now....

Both engines are out of the bike now. Carolina Cycle should be shipping my new big blocks and pistons early next week. I have to farm out more and more all the time because I'm never home. My engine builder needs to finish stripping the engines, then the cases can be bored for the bigger sleeves. I'll certainly post some pictures once we start stacking the engines, they will both be 1316cc, 15:1 compression. I'm going to install a couple of Dyna 2000 ignitions as well.
Hopefully the modified coupler will hold things together, if not, we'll try another idea. I want to run the bike again this year with the GSXR fairing. If the drive train issues are solved, its getting a very slippery body next year.
 

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #31 ·
With multiple engines, there is actually always a lead engine. This can be accomplished by simply changing the timing by a couple of degrees on one. As mentioned earlier, the bike was built in the early 90's and we have been trying to understand some of the reasoning behind the builder's decisions...most of them have been really well thought out. Upon tearing down the top ends, we learned that the cam specs were a little different between the engines, one head had light porting, the other was extrude honed...just little differences between the two. With the new overhaul, I'm trying to bring them a little closer. I agree, they seem to be out of synch. We've spent alot of time playing with the throttle cables. I know they are both wide open at full throttle, the problem is the bike has never seen full throttle...lots of wheel spin at anything over 3/4 throttle. 203mph at only 7 grand!! If it was easy, everybody would build this shit.
I still believe the coupler's idler was a weak design and the plan was to just lube the chain before each run. I'll see if I have a picture of the updated coupler and the new upper chain guide. I'm going to install a chain lube system as well, its going to make a mess but hopefully it will help. I've only run the bike on the short course, its got a long way to go before I trust it on the long course. I plan on retiring my Busa this year, the Double is way more fun!!
Cheers,
Scott
 

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #32 ·
This is the current coupler set up. I went with a 530 oring chain, it was a non-oring chain before, it should retain some of the lube. The idler sprocket is now steel, the old one was aluminium and it got loose on the bearing after we baked it a few times. Again, I'll add some sort of chain lube system.

All we can do is try and hopefully move forwards. I appreciate your suggestions.

Scott
 

Attachments

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #44 ·
To answer some of your comments...

Yes it has both clutches and transmissions, they are both shifted together, it is the countershafts that are coupled together.

As shown, yes there is a cover for the coupler, with a bit of work, it could be made oil tight.

Its too long to fit on a dyno. I would estimate the previous 1255cc engines were each capable of an honest 175 rear wheel hp in a conventional bike. I'm sure we lose a bit through the coupler and probably lots when we are frying it.

No, it didn't need more hp considering the wheel spin and the weak coupler but I consider big blocks to be the "holy grail" of oil coolers so I was happy that I scored 2 new ones. We'll also add some ballast and improve the rear suspension in hopes of helping it hook up.

Thanks again for your suggestions!

Scott
 

Attachments

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #46 ·
Ohhh what was I thinking?...this is what it looked like when it showed up at my local Suzuki dealer after having it shipped to Alberta from Pennsylvania. I was stuck on a rig in Mexico and they sent me this teaser shot.

It had not run in over 15 years. I was happy to score a Performance Machine "Chicane" front rim that matched the rear. I wan't really feeling the old spoked top fuel rim. It had drag slicks on it, which is odd because they are illegal at Bonneville and the bike had passed tech there a couple times.

I ordered a land speed front fender and early GSXR competition fairing from Air Tech. I think I bought 3 fairing mounts off ebay before I got a good one. It had a pair of rechargeable tachometers which I figured were junk from being so old, I replaced them with a couple of Trail Techs, cheap and easy.
 

Attachments

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #51 ·
The new chain has one less link than the one we thrashed, it is also has a rivet master link where as the old one had a clip style which was certainly easier to install. The 2 counter sprockets and the chain are installed at the same time now, it probably doesn't show in the picture but you end up spreading the counter sprockets as far as you can to get them on and its pretty tough with the short chain. Its not possible to remove another link, I wish it was.
Yeah, we'll just stick to the short course and inspect it after every run.
The record is only 208mph in this class, obviously we are looking to shatter it, not many of these old twin engine dinosaurs left. It was last set in '79 by Tom Elrod on a twin engine Kawasaki.
 

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #53 ·
I'm stuck in sandy Saudi Arabia for the next month or so. I'm looking forward to getting back in my garage and enjoying a beer while I have a good look at the coupler.

I certainly appreciate all of the positive suggestions. I'm definitely interested in trying to run a larger idler, I'm undecided about two of them.
I've saved Posplayr's diagram (THANKS!! I don't even know how you can make something like that..very cool) and will run it by my engine builder and team mates.

Whatever I do this year depends on how much time that I get home. The engine rebuilds are dragging on, I'm told today that my new big blocks and pistons are being shipped but I've heard that every week for a month. I definitely need to get the engines back in the bike and we'll go from there, it will probably be an all night thrash as usual but thats racing. If all goes well, I'll focus on finishing up my 1693cc Busa when I get home and my engine guy can play with the Double once I do the grunt work and install the engines. We do have some ambitious long term projects for the Double, I want EFI.
 

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #55 ·
Thanks, I appreciate that!
I always plan on running Speed Week every year in mid August. That is put on the table immediately with who ever I work for, non-negotiable.
El Mirage is 28 hours straight from my place, there are only two 2 day events each year, one in May and another in November, its hit or miss with my schedule and its too hard to justify the travel for the 1 day events.
 

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #56 ·
Here's a teaser....

This is the body that we will be running next year, this is sitting loose on a Buell but you get the idea.

Although bikes have a small frontal area, they suck aerodynamically because they are too short, the air never gets a chance to re-attach which results in drag. A long bike like the Double has the chance to be very slippery. It also helps that the SCTA has relaxed some rules concerning the rear of the bikes, length, height, amount that the wheel is covered etc.

So once we get the coupler sorted, we're planning on going fast!
 

Attachments

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #62 ·
Update.
I discussed the suggestions made for adding a second idler / tensioner to the Double's coupler with my engine builder and the bike's original builder. They offered valid points on why there should only be a single tensioner.

There should never be a tensioner or idler on the pull or "power" side of the chain. This is engineered in to every type of drive on the market today, from cam chains to drive chains. The power side should have as direct of a line from driven to drive as possible. Besides being totally redundant, a tensioner on the power side would see insane forces acting upon it under full throttle.

Since the front engine (lead engine) will be pulling harder than the rear, the top of the chain will be the "power" side. So the the additional tensioner would have to be as heavy duty as the drives themselves to be done right. Having said that, since the bottom of the chain will still be the slack side, that's where the tensioner needs to be.
The bottom will only have tension on it during deceleration and that force is substantially less than full throttle.

Run a bike on the dyno and watch what the chain does under power. Its totally slack on the bottom and whips up towards the swingarm while the top power side of the chain sucks down the suspension, its pulling so hard. Thats the reason behind putting the tensioner on the bottom.

We will definitely increase the idler gear size to reduce it's speed, heat and wear. Again, we will add a chain lube system.

The 530 chain should be more than adequate for the job. Have you ever seen double side plated 630 chain for top fuel bikes??!!

I appreciate your continued interest and support.

Cheers,
Scott
 

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #64 ·
I concur with the advice of where to place the tensioner. I did mention those high forces on the tension side previously.

Your 530 chain may serve you well for your purposes; several short runs lasting several minutes under load. My charts indicate that 530 chain is getting close to recommended max depending on your horsepower and rpm at the countersprocket. Again I would just measure chain stretch frequently

Not sure why you added chain guides, but I wouldn't restrict the chain movement on tension side. I never put chain guides on any design I've done, with loads far exceeding what you have here.
It may not cause you any issues, but chains will move up and down naturally on the tension side and by restricting that movement, those guides are putting forces on that chain and sprockets you really don't need, and at the least are robbing you of horsepower. I could send you a scan of a engineering design text that outlines this (scan too big to post here).
Yes, please email me the scan at [email protected]
Thank you!
 

·
Likes to race old junk.
Joined
·
2,978 Posts
Discussion Starter · #67 ·
Update.... Progress has been slow, I was overseas for 4 months in Saudi...my engine guy went through a divorce and I had to wait for him to build a new shop...there were many delays with the new big blocks but I finally recieved them...they are very nice with custom 15:1 JE Pistons, blocks were cut for o-rings...cases can now go out for machining...a new idler with a bigger sprocket will be fabricated...the new body from Air Tech will be shipped this month...lots of new upgrades are planned such as Dyna Tech ignitions, new rear suspension, provisions for adding lead ballast etc.

I didn't get a chance to run at Speed Week in August...I got home in mid July and just wanted to chill for a couple weeks, fixed my fence, worked on the race trailer, spent some time with my wife and dog, took some old bikes to a vintage rally...started getting the big Busa ready for the dyno, couldn't get any oil pressure out of the new 1697cc engine, didn't care for the stress and decided that this was starting to feel like work, cancelled my hotel and sold my entries...the Busa brings me sponsorship money and I wasn't interested in just running my R1 or 600RR.

I took a '75 250 Montesa and a bunch of parts that I'd been collecting and started building a cool vintage flat tracker, I shortened the sub frame, I've got an expansion chamber being built for it, parts have been sent out for painting, front and rear suspension are getting rebuilt...I stuffed a turbo in my '86 1100...drove my KLR to Yellowknife for a northern adventure.

I've just returned to Dubai...the Busa and the Double's engines and coupler are now with my engine builder...I'll miss any September events at Bonneville and the World Finals in October are unlikely. I hope to run something at El Mirage in November. Regardless, I hope that when I return home again that I'll be able to put the engines back in the Double and mount the new body.
 

Attachments

1 - 20 of 145 Posts
Top