Building a race bike

GregT said:
No. The layout of the box with a direct top on the side opposite the clutch is almost unique today. If you used a Japanese - or practically any other modern box - the final drive would come off the layshaft. Which raises problems of sprocket height and position vs the swingarm.

Red - a 180 will fit on a 5in rim as has been said before. I'd suspect that tyre clearance is your problem rather than rim. A coarse file can be used on the extreme edges of the tyre...Can gain you around 5mm.
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Chain clearance to the tire and the rear shocks as well as chain-wheel clearance to the swing-arm are the issues, everything else should be wide enough for a 180.

To solve this, you could extend the main-gear shaft and have a counter-support with a bearing in an extended clutch/shifter cover to move the sprocket out 10mm. In that case, I suppose a wider swing-arm is necessary, else you might get in trouble with the chain-wheel and potentially the shocks, too (assumed you ride a twin-shock bike). In that case, a change to a central single shock would be the way.

But what do I know - Red has million times more experience and know-how than me, pretty sure he'll come up with a fantastic solution!
 
I think a Billet 4th would be a good idea for me to start with, along with the outrigged clutch release housing etc.
I think it unlikely I will need change the primary gearing as I already mentioned, my bike will be ultra light and have a good bit less torque than Red's triple. I also have a max tyre restriction of 130 so less grip. I doubt I will have the same issues although RPM may play a new game.
I will if possible use a needle roller between the main shaft and output instead of the bronze. We found this to be a good improvement on a lot of the oldtimer gearboxes we use for racing the cars.

Next job though this weekend will be the new oil pump design, lots of work to do there.

J

And a few little last minute adjustments to the clutch for ease of mind.
 
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I just had a look at a great picture of what seems to be Red's race bike, (Lovely Pic Red!!) Running slicks,
We have to use road legal tyres of 130 max width. , we have a gentle race compound possible in the options but nothing like the grip of a "big" slick.
I think the contact patch will be a much larger problem (or smaller if you know what I mean) than the ultimate strength of my gearbox.

Julian
 
I understood that the cantilevered tyres were for wide tyres on narrower rims, like for fitting a 130 on a WM3. Are you limited with rim width, Julian?
 
GregT said:
BEARS racing is a different thing. Red's spaceframes are an interesting exercise in making a post classic competitive against moderns. There are only a few mods needed to make one eligible for true post-classic class racing too - if he could be bothered. Looks like they're havinng fun where they are.
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nailed that straight up Greg, I have no interest at all in racing in Post Classic, I wanted to build a Laverda based race bike using every modern and engineering upgrade that I could to see where I could take them, so far we have smashed every track lap record for our class in Aussie apart from Sydney
BEAR's here in Australia means if someone wanted to they could go and buy a brand new Triumph 1200 Thruxton R with engine management, variable cam timing, traction control, fuel injection etc and they are allowed to run in my F4 Heritage Class because the engine sort of looks the same as a 1980 Triumph, FFS. Hence I am pushing my bikes as far as I can
Be the same as the modern Norton's, they would be able to race in F4

You could actually run a TZ750 Yamaha in a British built say Spondon frame in F4 under Aussie BEARs rules, thankfully that has not happened yet, if it does I'm out. There is no way we could compete against a stink wheel
Was actually proposed by a certain competitor in 2019.
 
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redax5 said:
You could actually run a TZ750 Yamaha in a British built say Spondon frame in F4 under their rules, thankfully that has not happened yet, if it does I'm out
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Nah, you would just go out there and beat it. Most TZ750 motors got destroyed in outfits after they weren't competitive any more as solos. From my experience very few people race them in classic.
 
julian said:
To be honest if Red can make his gears work I doubt I will have a problem with a lot less weight and torque. We will see.
Fun stuff.
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Pulled the engine on the spare race bike today, surprisingly we have not lost a gearbox, we actually broke the cam chain tensioner blade in half which has decided enough is enough and jammed itself in between the crankcase body in the gearbox apartment and the selector drum cutouts thus not allowing the selector drum to turn
Had a few of those tensioner blades break now on our race engines but that is the first to cause an actual issue

Julian, checked spares today, have 2 off each final drive output shafts with extended nose and also 2 off each 4th gear billet gears
I need to keep at least one of each as spares for my race engines, you can have the other sets

Will dress the 4th gears with LG2 Bronze bushes with reverse oil scrolls and hone them to size this week
Can send you billet 4th gears and the billet output drive gear/output shaft next week, may be a delay on the hydraulic cover with bearing support though
I have one in stock that has Redax Laverda machined in it but no blank covers so ordered more yesterday

how much HP are you looking at on this engine, just roughly?
one of the early limiting factors I found was the engine case studs, piss weak when trying to hold even half serious power
we machined custom engine studs for the 8mm and 6mm studs though went for 10mm instead of those piss weak 8mm rolled studs
solved a lot of crank issues
 
We are limited only to a tyre size in the 750 class but not much point in going to silly rims with narrow tyres. Funily enough my tyre size is the same as the TZ750s ran in period. 130 rear 100 front.
I like Red's concept, as this is also his business and they go hand in hand.
For me I simply want to push the boundaries of the period and the class rules as far as possible although it is borderline I am trying not o go over the border. That's the name of the game of course.
Avon do a few interesting road/race compounds and no doubt I will need to experiment a bit. running it on road compound for shakedowns and worry about that later.
J

I think a TZ 750 taken to the limit with modern internals and modern 2 stroke techniques would piss all over anything out there. You just could not compete against a bike that light with possibly 160hp and I am not joking, they see well over that number in drag racing with the Kawasaki 750 triples and keep them reliable so a TZ would most likely be on another planet. (If it would be controllable which I think it may not be)
 
redax5 said:
Pulled the engine on the spare race bike today, surprisingly we have not lost a gearbox, we actually broke the cam chain tensioner blade in half which has decided enough is enough and jammed itself in between the crankcase body in the gearbox apartment and the selector drum cutouts thus not allowing the selector drum to turn
Had a few of those tensioner blades break now on our race engines but that is the first to cause an actual issue

Julian, checked spares today, have 2 off each final drive output shafts with extended nose and also 2 off each 4th gear billet gears
I need to keep at least one of each as spares for my race engines, you can have the other sets

Will dress the 4th gears with LG2 Bronze bushes with reverse oil scrolls and hone them to size this week
Can send you billet 4th gears and the billet output drive gear/output shaft next week, may be a delay on the hydraulic cover with bearing support though
I have one in stock that has Redax Laverda machined in it but no blank covers so ordered more yesterday

how much HP are you looking at on this engine, just roughly?
one of the early limiting factors I found was the engine case studs, piss weak when trying to hold even half serious power
we machined custom engine studs for the 8mm and 6mm studs though went for 10mm instead of those piss weak 8mm rolled studs
solved a lot of crank issues
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Hi Red,
Not in a rush, I have enough to do with other things, Thanks, please send all when you have it.

I want to see 120hp at about 11500, As mentioned before the dyno sym software I have has proved super accurate in the past as long as the input is real, which I make absolutely sure it is. from past experience I do not see any reason why I could not achieve this and more with the head flow figures I have, the new combustion chamber shape and the RPM. But as I mentioned before, torque will be well down on your numbers. Although in theory I should have a very nice spread of power once she comes on song. Time will tell.

I have all my main engine studs made in MP35N which is the pretty much the absolute strongest material available for studs, All made for me by TK Precission in the UK. Am fairly confident these should hold well. I did read about your stud issues Red and took note a long time ago, (you are being watched :geek: ) hence investing lots in the MP35N studs. With high tensile ARP nuts. For comparison an ARP Custom Aged 625+ stud has a yield of 270-290ksi, MP35N in Cold rolled and heat treated form has a min of 300ksi. Have also used steel inserts in the block threads.

Regards,
J
 
I think Battos race twin topped out at approx 80hp at the wheel so that's heaps more. Boy that bike sounded the beans.
 
Well if you think about it, I would be pretty dim to go to all these lengths if I were aiming for the same power as others have achieved with less effort.
This is a fun trip for myself to show to myself that what I have learned will work. I always try to do things my way, and although I learn from others I rarely listen to others (if you understand what I mean) in my life I have never listened to nay sayers, they are always wrong.
If I get there I will be happy, if not I will try harder.
I am throwing every single thing that I have ever learned at this project and am enjoying it immensely. Fingers crossed.
J
 
GregT said:
No. The layout of the box with a direct top on the side opposite the clutch is almost unique today. If you used a Japanese - or practically any other modern box - the final drive would come off the layshaft. Which raises problems of sprocket height and position vs the swingarm.

Red - a 180 will fit on a 5in rim as has been said before. I'd suspect that tyre clearance is your problem rather than rim. A coarse file can be used on the extreme edges of the tyre...Can gain you around 5mm.
Click to expand...
Hi Greg,
maybe you understood me wrong or I am wrong regarding the latest bikes.
I met him 1990 January in Ruapuna and later I visited him for an interview at his home and that time he told me he is using the shafts and gears of the GSXR- not the box. But maybe you know it better.
There is a picture of the old folder of that bike.41C03D0A-7241-426C-80FF-A3828F0B7BCC.jpeg
 
andre g said:
Hi Greg,
maybe you understood me wrong or I am wrong regarding the latest bikes.
I met him 1990 January in Ruapuna and later I visited him for an interview at his home and that time he told me he is using the shafts and gears of the GSXR- not the box. But maybe you know it better.
There is a picture of the old folder of that bike.
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I worked briefly for him at the time the first version was being raced - the one in your pic. That version used GSX1100 boxes - the earlier air cooled engine. The Mk2 version - with funny front end - went to GSXR1100 boxes. He was aware I'd built a GSXR1100 with the 750 six speed box - and made it live - so i got asked if he could make it work in the twin. i said No. Too much torque.
Funnily enough the first job i did when i started there was opening the packages containing parts of a new GSX1100 gearbox and assembling it. No manual of course - so off to the ChCh public library and take photocopies of the relevant pages from a Haynes manual. Handed them to john and said - Here's the start of your workshop manual for the bikes.....AFAIK, none was ever produced.

Julian - your HP target looks feasible. What hasn't been mentioned about the Aussie - and NZ - post Classics is the literal elephant in the paddock. The GSX1100 Suzuki's on methanol making close to 200HP.....Another very good reason to stick to BEARS racing.
 
Hi,
I think 120 should be feasible, but I do know it won't be easy, in theory it is certainly achievable but will remain to be seen. Airflow certainly is there in theory at least, and still with 43 and 36mm valves and relatively small ports to keep as much tractability as poss.
I think the big question will be how easy it is to get the cam and exhaust to match. In the past the exhaust has proved to be a real winner or killer in the power stakes even more than the cam.
Will keep you all informed on how it goes.
Regards,
J
 
Tippie said:
Nah, you would just go out there and beat it. Most TZ750 motors got destroyed in outfits after they weren't competitive any more as solos. From my experience very few people race them in classic.
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Andy Bartlett came up against one at a CMRC meeting before he had his engine Redaxed. The TZ just disappeared into the distance so he switched to BHR Bears to be competitive.
 
Aussie BEARS rules are looked on with suspicion over here. We've had bikes turn up for the Sound of Thunder from Oz that have been raced in aussie BEARS but are not eligible here. As Red quotes, jap engines in legal frames.

The broken cam chain tensioners interest me. I've run a lot of race engines with camchain setups similar to the Laverda but my personal sample is only the one race Laverda. Which with big cams has given no problems at all. Red, are you running a manual tensioner or spring loaded type ?
I know from experience with Suzuki's the spring loaded type can be made to oscillate which will usually break the blade.
Back in the day I've seen a steel rib welded onto the back of a tensioner to stiffen it. Obviously very difficult to avoid losing the bonded rubber - but it can be done.
The best modern I've seen is a couple of guys in Auckland doing a tensioner kit for the 16V Honda's. Their blade is CNC machined from a hard strong plastic. Much bigger section than OE - about 30mm deep front to back at the thickest point and about 15mm thick. Pretty well unbreakable.
 
This is a very interesting and informative thread, much more so than the ' is it a jota or not thread', blah.
My question is what bikes can run in the Phillip Island Classic specifically the International Challenge, 1970-80s era bikes. I read an article on a bike that raced there, 83 FJ1100 in a Harris-built Suzuki? XR69 chassis, it sounds like it is more in the vein of a "Run what you brung" class as long as it is '70s-'80s. What classes does the Redax Laverda run in?
 
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