Author Topic: 35mm fork (Read 29825 times)

turboguzzi · « **on:** November 06, 2009, 01:29:11 pm »

Hei hi-per's

The list of upgrades for next year's season is growing longer. Plenty to do this winter.

among the problems I've encountered in the last races was the onset of chatter at the front. One possible source for it accoridng to some, could be the non bushed stock fork. It's not only that chromed steel and aluminum dont liek to slide over each other so much, it's also the fact that with a bush-less fork like in our SOHC's, deflection in the fork tubes under high cornering forces can cause binding.

So then, is anybody aware of any japanese bike that uses 35mm forks AND has a top and bottom bush? regretfully I am limited to 35mm forks in my class, otherwise I could have a lot more options.

TG

voxonda · « **Reply #1 on:** November 06, 2009, 01:46:37 pm »

Hey TG,

There are several options. Honda's 1st 750 fork has bushings but not really suited for racing IMHO.
Better options are the Honda VTR250, or the (much) cheaper Yamaha RD350 31K, or the even better dampened RD350 F2/N.

Good luck with the search.

Rob

turboguzzi · « **Reply #2 on:** November 06, 2009, 02:06:51 pm »

Good tip, tnxs!

How's the dry clutch coming along? doing burn outs already?

TG

voxonda · « **Reply #3 on:** November 06, 2009, 02:16:01 pm »

Ah, forgot one. Use a 35 mm Moto Guzzi fork in my replica although no bushings it has cartridges.
Am really busy lately and not much time left, but it 'll come!

Rob

turboguzzi · « **Reply #4 on:** November 06, 2009, 02:24:40 pm »

got a few guzzi forks here (after all, my nick is turboguzzi for a reason...) but indeed, that's not what I want.

will save them for when I get around to restore or racerize my LM III 850.

TG

Bill/BentON Racing · « **Reply #5 on:** November 06, 2009, 04:05:17 pm »

TG,you are where I was as far as f/end.Your chassis improvements,modern tires and aggressive riding all add up to CHATTER with stock 35mm Honda forks.If I had run mine again I had swore it would be w/a different f/end! Ceriani,VTR250,RD's?,I was looking @F2 CBR,but not 35mm.Very interested in what we can find out,The rear end got fixed w/Fox Superbike shocks,welded/braced swingarm,and needle bearing kit.Never got the the front right,got worse as tires got better!,Bill

voxonda · « **Reply #6 on:** November 07, 2009, 12:55:16 am »

Problem is in regulations, in a lot of countries you are only allowed to use the 35 mm. IMHO correct, we are talking "classic racing" here. But even a 35 mm can be improved a lot, at least in conjunction with period race tires. Not with the modern rubber.
Once tried slicks on a 750, you will never get that right.

Rob

bwaller · « **Reply #7 on:** November 07, 2009, 05:03:41 am »

I was hoping the longer fork legs from a later model 550 or 750 might help eliminate some of that binding by offering more support, as long as both tubes & legs aren't badly worn.

Perhaps this is something someone can develop, bushed front forks. There ought to be lots of worn out legs to work with!

754 · « **Reply #8 on:** November 07, 2009, 12:57:40 pm »

77 & 77 750 K forks have a longer lower fork leg. Should note here CB 500 are shorter than 750 legs. I think the extra engagement on later forks may help.

Also if wear is fairly consistent (or legs are honed), forks can be hardchrome plated and made bigger, ie fit fork better.

Not sure if Ceriani are double bushed, but they are currently around 1700.00 Euros, for legs, less trees, plus I think they are shorter, top tree gos down a long way.

Stock forks could certainly be bushed, a bit of work though.. top bushing would be easy, the lower would be more difficult.. anyone got an idea how far apart they should be?

MCRider · « **Reply #9 on:** November 07, 2009, 02:07:08 pm »

Quote from: turboguzzi on November 06, 2009, 01:29:11 pm

Hei hi-per's

The list of upgrades for next year's season is growing longer. Plenty to do this winter.

among the problems I've encountered in the last races was the onset of chatter at the front. One possible source for it accoridng to some, could be the non bushed stock fork. It's not only that chromed steel and aluminum dont liek to slide over each other so much, it's also the fact that with a bush-less fork like in our SOHC's, deflection in the fork tubes under high cornering forces can cause binding.

So then, is anybody aware of any japanese bike that uses 35mm forks AND has a top and bottom bush? regretfully I am limited to 35mm forks in my class, otherwise I could have a lot more options.

TG

The early CB750 fork is bushed , thru and incl K2. Or am I not understanding the question. I had my bushes teflon coated to decrease frictions and clearances.

I'm wondering though if the bushless forks might be better with the lower leg cryogenically treated and install Racetech emulators.

754 · « **Reply #10 on:** November 07, 2009, 08:47:36 pm »

The early 750 only has an upper bushing I believe, that can be custom made to take up the wear.

However if the lower part of fork tube, has 5 or 6 thou wear, a tight uppper bushing wont fix that..

MCRider · « **Reply #11 on:** November 07, 2009, 10:09:47 pm »

Quote from: 754 on November 07, 2009, 08:47:36 pm

The early 750 only has an upper bushing I believe, that can be custom made to take up the wear.

However if the lower part of fork tube, has 5 or 6 thou wear, a tight uppper bushing wont fix that..

Again I'm not sure if I'm speaking correctly...

But the early 750 fork has a bushing about 2 inches long that is held in the top part of the lower leg and the tube slides thru it.

The lower bush, also about 2 inches long is affixed to the tube with circlips, is removable and slides in the lower leg. No part of the tube ever actually touches the lower leg.

754 · « **Reply #12 on:** November 07, 2009, 10:45:29 pm »

Well, it sounds like 2 bushings then, but because one is on the tube, the fork leg still wears, unfortunately more higher up, than at the end of the travel.. so the lower bushing on the steel forktube IS TOUCHING the forkleg wall, and will wear in a tapered fashion.. hard to remedy over complete travel of the fork.

On a dual bushing fork leg, NOTHING rubs against the fork leg, just against the 2 bushings.. When these wear out, you replace with correct size, then ream or hone to fit, back to original spec (if fork steel tube is not worn)

Rod · « **Reply #13 on:** November 08, 2009, 04:36:15 am »

TG - several suggestions:

Yamaha TZ 350 forks (35mm & made for racing) I'll measure the fork length on mine if interested

or contact Maxtons in UK who do fork conversions on most Classics for racing

or try Peter C for some ideas, his hailwood replica performed very well, I have his email somewhere if needed.

Rod

turboguzzi · « **Reply #14 on:** November 08, 2009, 04:47:58 am »

many interesting ideas here, a quick price check shows that late RD's might be the best budget oriented option.

Dont even want to think how much true TZ forks might cost....

I have the big Milan swap meet coming up soon, so will know better what to hunt for.

interestingly, having twin Teflon bushes do not always mean that the fork legs are safe from wear. My stock GSXR 1100 L model suffered from sever wear in the fork lowers due to bad design. I managed to solve it with Bandit 1200 sliders that are longer and therefore have more overlap on the tube. For the record, I did saw the old legs in the middle and was shocked by the amount of wear, the bore was oval by something like 1.5mm (about 1/16")!

TG

fishhead · « **Reply #15 on:** November 08, 2009, 05:11:36 am »

Trickit made fork bushing extenders in the 70's. They would mount to where the stock fork seal went and have a teflon lined "bushing" to help eliminate play/chatter and stiffen the front up (some).
Pic shows them installed on a set of 36mm forks (KZ 900). They made them in 35mm also. Something simular could be easily made for the 35mm fork tubes.
Can you run a fork brace?

bwaller · « **Reply #16 on:** November 08, 2009, 07:01:12 am »

It would be cool if something could be done with stock legs. One downside with an RD fork set-up is only one leg will have lugs for a caliper. Fine if the plan is to use one disc though.

754 · « **Reply #17 on:** November 08, 2009, 08:35:59 am »

Not sure if Betor has bushings or not, but they are cheaper than Ceriani, and pretty light. Early CanAm,s came with fender mounts on 35mm with 15mm axle.

I been thinking obout the CB forks, I think I could set up to bore them out, the trick then is to find thin wall bronze to bore out for bushings.. to keep cost somewhat reasonable..

MCRider · « **Reply #18 on:** November 08, 2009, 09:11:31 am »

Quote from: 754 on November 07, 2009, 10:45:29 pm

Well, it sounds like 2 bushings then, but because one is on the tube, the fork leg still wears, unfortunately more higher up, than at the end of the travel.. so the lower bushing on the steel forktube IS TOUCHING the forkleg wall, and will wear in a tapered fashion.. hard to remedy over complete travel of the fork.

On a dual bushing fork leg, NOTHING rubs against the fork leg, just against the 2 bushings.. When these wear out, you replace with correct size, then ream or hone to fit, back to original spec (if fork steel tube is not worn)

I see what you're saying. Never mind.

turboguzzi · « **Reply #19 on:** November 08, 2009, 01:57:56 pm »

Quote from: fishhead on November 08, 2009, 05:11:36 am

Trickit made fork bushing extenders in the 70's. They would mount to where the stock fork seal went and have a teflon lined "bushing" to help eliminate play/chatter and stiffen the front up (some).
Pic shows them installed on a set of 36mm forks (KZ 900). They made them in 35mm also. Something simular could be easily made for the 35mm fork tubes.
Can you run a fork brace?

nice idea, never knew about these. Could be an interesting back up solution.

I am running a tarozzi fork brace.

Ricisan · « **Reply #20 on:** November 08, 2009, 03:11:33 pm »

I have some 35mm forks that I was told came from CB900/1000, I forget which.
What they do have are the Gen II brakes w/dual pistons.
I had to thin the stk rotors to fit the calipers, then I had to move the calipers closer together to match the rotors. I have 2.5/3.5 rims on stk hubs. The rims are polished and very cool. The tubes fit perfect, but a little long.
I used washers stacked up for a spacer w/calipers. I know that won't do. Having a custom spacer made could get a little expensive. I don't want to skimp on the brakes, are there any other proper fixes?
The system bolts up well and has to be virtually taken apart to get the wheel off.
It was easier than I thought to upgrade brakes. I don't want to ride w/stk!

R

turboguzzi · « **Reply #21 on:** November 08, 2009, 03:29:18 pm »

a picture might help....

kos · « **Reply #22 on:** November 11, 2009, 10:19:22 am »

If you really want to get some great fork action on the front of your ride...go wth 1982 CB750F DOHC forks. Sure they are larger OD (37mm) but the have the Honda dual syntallic bushings on them and the can be re-valved with Race Tech (sponsor plug) Gold valves.

Won Daytona 7 times with these forks!

KOS

turboguzzi · « **Reply #23 on:** November 11, 2009, 10:21:18 am »

Quote from: kos on November 11, 2009, 10:19:22 am

If you really want to get some great fork action on the front of your ride...go wth 1982 CB750F DOHC forks. Sure they are larger OD (37mm) but the have the Honda dual syntallic bushings on them and the can be re-valved with Race Tech (sponsor plug) Gold valves.

Won Daytona 7 times with these forks!

KOS

wish I could, rulebook says 35mm....

mec · « **Reply #24 on:** November 11, 2009, 11:17:31 am »

early cb900f does have 35er

mec

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Author Topic: 35mm fork (Read 29825 times)