600/750 swinging arms?

[Mr Gazza]

Dukedesmo. Thank you for confirming comprehensively that all the swinging arms interchange. It now seems that I am fitting Y2000 M750 arm to Y2000 750SS, thanks to Jeff, so all should go smoothly. Very good info for future reference too..

Yes, please put my name on your spindle, it could well come in handy for this. I will get in touch when we look likely to meet up on a run and arrange to swap parts/money/ beer/breakfast whatever..

Nasher. Good call with your alloy swinger. I was tempted to try and find an alloy one, but steel actually suits my plans better for this project.
Alloy swingers are sought after and not often offered for sale so you shouldn't have to wait too long for a customer… And very importantly, thanks to Dukedesmo we now know that your alloy arm will fit all the hoop models, so lots of folk who could potentially upgrade.

My good friend Dacs also has a steel swinging arm for sale from a 620ie, which has rod and not hoop suspension and also a 25mm axle. This should fit all the ie models until S*R.
(I was going to use this on my 750, but the 25mm axle put a spanner in the works.)

Darren... No!

[350TSS]

The m750 arm has a suspension that operates via a rocker the SS750 is a plain "cantilever" .

The M750 frame has a strong point that holds the pivot for the rocker. the ss750 has none.

If you are preferring a steel SA I suspect two additional welded brackets on SA and a couple of plates onto the ss750 frame to take twin shocks? cannot help but speculate.

[Mr Gazza]

Ha ha! That's got you thinking..
Actually my first thoughts were to use a Paso swinger because I love the look of the eccentric adjuster in the alloy arm.
Sadly there is only enough room for the Paso's 16" wheel, the bearings are in the arm, not the engine and it's much longer than the SS or Monster arms. It would almost be easier to make bespoke, than to do all the mods to the Paso arm.

[utopia]

I've never owned a bike with eccentric chain adjusters so I can't speak from "hands on" experience but I've always thought that they looked very prone to cause inaccuracies in wheel alignment.

[350TSS]

Not so sure about changes in wheel alignment - why would it be worse than a slot?

What they I think do is alter the ride height, if the relationship between the the two eyes of the shock is taken as a constant and it should not change because the weight of the bike has not changed, then moving the eccentricly mounted rear wheel spindle further away from the SA pivot must move the top eye of the shock mount down.

The distance between the rear wheel spindle and the contact patch of the tyre is obviously also a constant

[Darkness]

Originally Posted by 350TSS

Not so sure about changes in wheel alignment - why would it be worse than a slot?

What they I think do is alter the ride height, if the relationship between the the two eyes of the shock is taken as a constant and it should not change because the weight of the bike has not changed, then moving the eccentricly mounted rear wheel spindle further away from the SA pivot must move the top eye of the shock mount down.

The distance between the rear wheel spindle and the contact patch of the tyre is obviously also a constant

Yes, if the back axle needed to be half way back on the adjuster to get the right chain tension you would have a choice of positions for the axle, 12 o’clock or 6 o’clock giving a difference of an inch or so on rear ride height.

[mickj]

Originally Posted by utopia

I've never owned a bike with eccentric chain adjusters so I can't speak from "hands on" experience but I've always thought that they looked very prone to cause inaccuracies in wheel alignment.

I had a Triumph Trident 900 with eccentric chain adjusters for 11 years and never had any problems with alignment. It's a very simple system and easy to adjust.

[Mr Gazza]

I think adjustment is effected by keeping the spindle and wheel locked tight onto the two captive cylinders and then rotating the whole assembly in the swinging arm. So wheel alignment remains the same (as from manufacture) and only chain tension changes.
I can see that you're thinking the wheel could be tipped over from top to bottom if one adjuster went one way and vice versa, but I think adjusting it nipped up, as above, would keep that under control?

I had foreseen the advantage of some ride height adjustment, but it would only be a choice of a high and low range, the amount depending on chain condition. If I managed to get the new suspension mounts set up in the ideal position, I would have to be deciding on whether to run it higher or lower than ideal.. Better to try and get the ride height set statically as close as possible to the original SS set up (or what I calculate to be ideal for purpose) and then incorporate some sort of adjustment into the suspension mounts, or neater still buy suspension unit(s) with ride height adjustment incorporated.

I found the handling on my last 750SS to be very "sharp", but rear wheel traction could be very easily compromised at the wrong moments! My hope is to retain that lovely Italian "sharpness" but introduce a bit more stability. Weight distribution and carful suspension tuning are key to this... Time will tell..

[utopia]

Originally Posted by Mr Gazza

I think adjustment is effected by keeping the spindle and wheel locked tight onto the two captive cylinders and then rotating the whole assembly in the swinging arm. So wheel alignment remains the same (as from manufacture) and only chain tension changes.
I can see that you're thinking the wheel could be tipped over from top to bottom if one adjuster went one way and vice versa, but I think adjusting it nipped up, as above, would keep that under control?

Yep, that matches my thinking.
If the spindle can remain locked to the eccentric cylinders during adjustment then the inaccuracies that I was anticipating would be avoided.
Its not easy to tell from the pics whether this is the case or not, but my concern arose from the "not" possibility.
I'll have a closer look to see what's what next time I get the chance.

[Dukedesmo]

Originally Posted by 350TSS

What they I think do is alter the ride height, if the relationship between the the two eyes of the shock is taken as a constant and it should not change because the weight of the bike has not changed, then moving the eccentricly mounted rear wheel spindle further away from the SA pivot must move the top eye of the shock mount down.

On my 916, adjusting the chain tension does indeed alter the ride height.

How much by depends on whereabouts the eccentric is set and where you move it to but if you want to keep the geometry the same then you need to alter the ride height accordingly.

Fortunately ride height adjustment is very simple, as is the eccentric adjustment and, because the eccentric is the entire rear hub/bearing assembly, chain alignment is not affected.

I tend to get round the whole chain tension/ride height conundrum by rarely adjusting the chain...

[350TSS]

I always liked the snail cam adjuster mechanism on my old 350TSS
Here it is re-created by AJR in Spain - yours for 15000 Euros

[utopia]

Yes, my old TL125/150 had snail cam adjusters and I quite liked those.

I've got a big soft spot for an aircooled two-stroke too.

[Mr Gazza]

Funny that you should mention snail cams, as after my hopes of eccentric adjusters were dashed, I thought snail cams would be just as nice. A kit for all Monsters would be easy enough to produce, maybe even an option of 17 and 25mm axles... Leave it with me..

[Darren69]

A few years ago I aquired a Metametchex arm for my S4 and although it is a beautiful piece of engineering above and beyond and replacing all tbe cast sections of the standard arm with billet it has eccentric chain cams and i dont like the idea of another suspension variable. I also think i prefer the look of the standard setup tbh as much for looks as much as any practical advantages or disadvantages as it were. So the bling is still boxed. Eccentrics make sense more on a single sider and i like the 851/888 look of the monster Albert it minus hoop.

[Darren69]

Oh btw i also had a Hinckley trumpet trophy and the adjustment is well engineered and trouble free, veru well built bikes but shame about the engines but thats another tale, the early ones anyway but i think the T595 still had issues too.