Rear Suspension tolerances

[RonBelfast]

Hi all,
just rebuilding the 660 Sport project bike and noticed some play in the swinging arm, up and down play, not lateral.
Seems to be the bolt at top of the monoshock unit, it is tightened but a there is a little bit of free play. Dont think the bush or the bolt are worn but is any up/down play in the swinging arm normal/suspension, I have the rear wheel off so it is more noticeable due to less weight. Would this be a MOT failure?
Many thanks
Ron

[tigcraft]

Mine had similar MOT problem this time round but at the bottom of the mono shock instead and had play in it although bolt was very tight. It had to be loosened then retightened otherwise a fail. Eric

[RonBelfast]

Hi Eric,
Did you have to replace anything? All bolts are tight on mine too but definitely some play there.
Ta
Ron

[edfmaniac]

Mine has the same problem and I plan on fixing it ASAP. You don't want any play at all in the swing arm, especially if you do anything other than very relaxed riding. Going around a corner at a decent speed with slack in the shock linkage could induce some very unpleasant events.

[arry_b]

There is a little "give" in the top bush of the shock, but far and away the most common cause of free play felt when you lift the rear wheel is from the spherical bearing in the shock linkage. It's really noticeable when you have the wheel out, there's a definite clonk when you waggle the swinging arm vertically.

The parts you need to repair the shock linkage are a pair of 16x26x5 oil seals and a GE12PB Steel / Phosphor Bronze Spherical Plain Bearing 12x26x16x12mm. Use Simplybearings.com for the parts if you're in the UK, they're a third of the price of Grahams.

It's worth drilling the linkage and fitting a grease nipple to the spherical bearing - unlike the original bearing, the replacement has a grease channel, so a few squirts with a grease gun every few months should mean you never need to do the job again.

[tigcraft]

Hi Ron, no I didn't replace anything. Just got a two foot strong bar on it. E

[RonBelfast]

Very good info here, and useful stuff.
I found the problem with mine was that the previous owner (I've only had the beek a few weeks) had not shimmed the top bush bolt correctly so even with the securing nut fully tightened it was able to move up and down. I re-shimmed it with correct washer sizes and problem solved.
Play is barely visible now.
Thanks
Ron

[hb7]

I have several Skorpions and all of them have the slop or play in the top shock bushing to bolt.
Must be a reason for it....me thinks.
I have never noticed anything from it while riding....

[Srinath]

Very good info here, and useful stuff.
I found the problem with mine was that the previous owner (I've only had the beek a few weeks) had not shimmed the top bush bolt correctly so even with the securing nut fully tightened it was able to move up and down. I re-shimmed it with correct washer sizes and problem solved.
Play is barely visible now.
Thanks
Ron

There is shims in the top shock mount ? I've never seen that on any bike, I gotta look.
Cool.
Srinath.

[Linegeist]

The top shocker mount is a metal/rubber affair, designed to flex with zero play. The centre bush is bolted tightly to the frame lug and there is no play at the bolt shank at all. The outer periphery of the bush is a press fit into the shocker mounting lug. There's very little actual movement, either axial or radial, at the top shocker mount - all the leaping about is done by the crescent bearings at the bottom - the top bush is simply there to absorb any undue stresses placed on the shock or frame lugs during deflection.

There should be NO play. Don't forget that the tiniest amount of slop at any of those mountings will be magnified disproportionately by the sheer length of the mechanical linkages involved - not least of which is the swing arm itself. A few thou in a worn lower crescent bearing for example will equate to a good centimeter at the rear axle.

If the top bush isn't obviously loose, then I would suspect that the rubber sandwich compound has gone soft and is allowing play to be felt at the rear wheel and, from previous experience with other bikes, changing out such a bush will have a most gratifying effect on the bike's handling. The job's dead easy to do ........ http://www.craske.myzen.co.uk/Skorpion/Page%201.htm