Beamish RL fork question

[djr]

Hello, 

Has anybody replaced the leading axle forks on a Beamish/RL with straight forks ?

The reason I ask is because the stantions on mine need re-chroming , £200 ish seems to be the going rate , but I have a spare pair of better Ossa MAR & Yamaha trials forks , and several wheels.

so would probably only need to buy some suitable yokes that go with the forks that I am thinking of using, to get somewhere near the right geometry.

I think I have seen this change from straight to leading axle on some other bikes ( and vice versa) but can't remember seeing a Beamish that has been changed.

I have access to a lathe & mill, so some small mods won't be a problem

Thanks 

 

[teamferret]

There's a good chance that the ossa fork stantions etc will fit nicely into the RL bottoms

[djr]

3 hours ago, teamferret said:

There's a good chance that the ossa fork stantions etc will fit nicely into the RL bottoms

Thanks,

I was thinking that today- nothing to lose in stripping 1 fork leg down on each set and doing some measuring.

Measured the O.D. of the Suzuki stantions today - 1 is 34.95mm , the other 34.8mm ( same readings in multiple places, not just measured in one place)  

So maybe the forks have already had some work ?, which is not surprising for its age

[suzuki250]

18 hours ago, djr said:

Thanks,

I was thinking that today- nothing to lose in stripping 1 fork leg down on each set and doing some measuring.

Measured the O.D. of the Suzuki stantions today - 1 is 34.95mm , the other 34.8mm ( same readings in multiple places, not just measured in one place)  

So maybe the forks have already had some work ?, which is not surprising for its age

The Suzuki ones are all smaller in Diameter

[djr]

7 hours ago, suzuki250 said:

The Suzuki ones are all smaller in Diameter

Thanks,

So should the Suzuki stanchions be 34.8mm or 34.95 ?

I have one at 34.8, the other 34.95

For comparison, I measured the 4 Ossa fork stanchions I have , and they measure - 34.95, 35.00, 35.00,35.05

So the Ossa ones are within 0.05mm of of the nominal size of 35mm

But the Suzuki vary by 0.15mm, I would have expected them to be closer

( All measurements taken with micrometer in several places, not one place)

The 2 different sizes make me think one stanchion has been replaced ? 

[feetupfun]

12 hours ago, djr said:

Thanks,

So should the Suzuki stanchions be 34.8mm or 34.95 ?

I have one at 34.8, the other 34.95

For comparison, I measured the 4 Ossa fork stanchions I have , and they measure - 34.95, 35.00, 35.00,35.05

So the Ossa ones are within 0.05mm of of the nominal size of 35mm

But the Suzuki vary by 0.15mm, I would have expected them to be closer

( All measurements taken with micrometer in several places, not one place)

The 2 different sizes make me think one stanchion has been replaced ? 

There is variability in tube diameter when tubes are made new and when they are re-chromed. The process of finishing them (centreless grinding) is not a precision process, nor does it need to be.

[suzuki250]

54 minutes ago, feetupfun said:

There is variability in tube diameter when tubes are made new and when they are re-chromed. The process of finishing them (centreless grinding) is not a precision process, nor does it need to be.

Not where I worked, we worked to microns (+/- 0.002mm)!

Edited May 11, 2023 by suzuki250

[feetupfun]

20 minutes ago, suzuki250 said:

Not where I worked, we worked to microns (+/- 0.002mm)!

Impressive. Are you saying that motorbike fork tubes are manufactured to that degree of accuracy on diameter?

[suzuki250]

16 minutes ago, feetupfun said:

Impressive. Are you saying that motorbike fork tubes are manufactured to that degree of accuracy on diameter?

I’ve never ground fork stations, but they would have to be accurate to avoid issues with fit tolerances in the slider bushes

 

[djr]

Hello Suzuki 250

You commented that the Suzuki stantions are a smaller diameter than 35mm , could you tell me what that diameter is please ?

As I mentioned, I have one measuring 34.8mm , and the other 34.95mm, is one the correct size , or are both wrong ? 

Thanks 

[suzuki250]

4 hours ago, djr said:

Hello Suzuki 250

You commented that the Suzuki stantions are a smaller diameter than 35mm , could you tell me what that diameter is please ?

As I mentioned, I have one measuring 34.8mm , and the other 34.95mm, is one the correct size , or are both wrong ? 

Thanks 

I'll measure mine tomorrow and let you know tomorrow

 

Edited May 11, 2023 by suzuki250

[djr]

11 hours ago, suzuki250 said:

I'll measure mine tomorrow and let you know tomorrow

 

Thanks

All interesting info

I am not a qualified engineer, and I have never been a motorcycle  fork manufacturer, so- I DON'T KNOW what an acceptable variation in size is for fork stanchions. 

Out of curiosity I have measured the 9 pairs of forks I have. (Kawasaki, Yamaha, Suzuki,Ossa,can am) all are 1970s & 1980s

Only 1 pair are within 0.02 of each other , the rest are 0.05 - 0.15mm different to each other.

Most are undersize, but a couple are 0.05 oversized. 

( Measured in multiple places with a micrometer, not one place with a Lidl Vernier)

I don't know what the correct tolerance is for fork stanchions, but all the forks I own don't appear to be made to micron tolerance.

Perhaps with modern manufacturing, the tolerances are better now on a new bike ?

[suzuki250]

I've measured two sets of RL forks and they are both 34.91mm with -0.01mm difference top to bottom

 

  

Edited May 13, 2023 by suzuki250

[djr]

6 hours ago, suzuki250 said:

I've measured two sets of RL forks and they are both 34.91mm with -0.01mm difference top to bottom

 

  

Thanks 

[djr]

If anyone is interested, I did eventually finish this job recently by fitting some betor stanchions I had into the Suzuki sliders.

Only problem being the sliders needed reaming on lathe to allow the betor stanchions to fit without sticking.

I know there are tolerances & variations, but after measuring several Suzuki forks they all seem to be closer to 1.3/8inch (34.93mm) than 35mm.

This is probably silly, but I am wondering if they are actually made to an imperial size?

All the other nominally 35mm forks I have, although they vary in size most are close to or just over 35mm.