Background: I have a spare frame that I bought a couple of years ago. Engine mounts had been modified to fit a different motor but along the conversion the owner got tired and sold off the frame (frame, subframe, swingarm and shock). A while ago I decided to take out the rear shock from my bike to renovate it and at the same time switch the swingarms from the spare frame (my original swingarm is missing one bobbin lug and has a few scratches from a chain that broke).

Today, when comparing the two swingarms I could se that they differed in several ways. Are these hand made modifications or is there a very similar swing arm that someone fitted? What do you think?

My original swingarm to the left, the spare to the right.

Is it possible that someone has gone to the length of removing the rear brake mounting slide thingy on the inside of the swingarm and leave almost no trace of it? Why not just leave it since it is not showing, beats me.
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MC21, GP-Replica (Daijiro Kato, Telefonica Movistar Team 2001)

Looks like someone has removed the rear caliper bracket to run the RS250 under slung rear caliper. It's a modification the TT-F3 race NSR's run.

The bracket looks like this



That wire thing hanging off the bottom isn't anything like the F3/RS250 arrangement. I guess it's because they didn't want to modify the swingarm to hold the typical anchor arm.

Is it just me or is that a total lash up! Hope I'm wrong but looks like a length of threaded stud being used as a brake torque arm, I wouldnt trust that on my push bike let alone a motorbike!

Some people just shouldnt be allowed to use tools!

Hi,

I work for a superbike race team and in the past we have modified swingarms so that the caliper mounts of a billet chain adjuster block with drop down brackets to mount the caliper. Now with after market wheels maybe they had a problem with the disc hitting on the standard caliper slider/block. As a result they removed it......

I have a friend who worked gp 250's, I'll ask him.....he may be able to confirm my theory.

Hope this helps

Regards Drew

P.s I'll take a picture of our current caliper mount to show you what I mean.

The 3 riv nuts on top look like they would suit a hugger of some sort.

Hi,

I work for a superbike race team and in the past we have modified swingarms so that the caliper mounts of a billet chain adjuster block with drop down brackets to mount the caliper. Now with after market wheels maybe they had a problem with the disc hitting on the standard caliper slider/block. As a result they removed it......

I have a friend who worked gp 250's, I'll ask him.....he may be able to confirm my theory.

Hope this helps

Regards Drew

P.s I'll take a picture of our current caliper mount to show you what I mean.

Here we go..... a picture of Roy's TT-F3 with a kit swingarm and rear caliper fitted. My guess is this is what they were copying

Dead right Tom, i've just fitted one these on mine, with the proper bracket welded under the swingarm, it looks like someones done the same but couldn't be arsed to go to the trouble of removing the swinger and welding on a fixing point for the brake arm, hence the length of threaded bar, which looks like it bent under the strain.
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Do I really need to point out what everyone's missing about the threaded bar?
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Andy.
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Andy wrote:Do I really need to point out what everyone's missing about the threaded bar?

He's only gone and used imperial gauge threaded bar rather than metric. Fool!

Where would the caliper be located? In which direction is the wheel rotating? What force will be applied to the threaded rod as the brake is applied?

After you have thought about those questions, ask yourself [a] how the rod probably bent (i.e. was he a stunt rider, riding backwards, or do you think it was simply bent during storage or something?!), and [b] how much stronger is a small-gauge threaded steel bar under tension than compression. Hold an undistorted length in your hands, and bend the ends towards eachother... then hold a length and try to distort it by pulling the ends away from eachother! Simple physics.

No, it's not an HRC spec modification, but neither is a lot of rubbish we see on NSR's and all other cobbled together "race" bikes!
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Andy.
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Thanks for all responses. It sure looks lika an intentional modifcation, but the real reason to why this was made, I guess we can only speculate.

I will take both swingarms to a welder and see what the difference in cost it would be to restore the modified swingarm and repair the original (missing bobbin lug)

I also found another interesting mod to the linkage plates. Has someone tried this modification (see picture)? I thought that the bikes in Sweden were all fittet with Öhlins rear shock by Honda Sweden wen they were brought here for racing purposes, but this frame I bought with a SP rear shock. To change the ride height I guess this modification was a better solution than just adding preload to the spring.
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MC21, GP-Replica (Daijiro Kato, Telefonica Movistar Team 2001)

Andy wrote:

No, it's not an HRC spec modification, but neither is a lot of rubbish we see on NSR's and all other cobbled together "race" bikes!

Hi!
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More **** two strokes than you can shake a **** stick at.

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Andy.
NSR-WORLD.COM

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paul g wrote:Is it just me or is that a total lash up! Hope I'm wrong but looks like a length of threaded stud being used as a brake torque arm, I wouldnt trust that on my push bike let alone a motorbike!

Some people just shouldnt be allowed to use tools!

It's a rear brake presumably for a race bike, unless you're Mick Doohan all it has to do is pass scrutineering, it will never actually be used. I know more than one racer who runs an aluminium rear disc to save weight.
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