swing arm bushes

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swing arm bushes

Postby dunk 1 » 26 Mar 2020 11:36

Hello -How much movement should there be between the bush and swing arm pin before fitting in the arm? ie how close is the tolerance.
When I stripped my bike for its overhaul I removed the bushes from my swing arm and a spare I had to see which tidied up best. The pin that was on the bike was quite worn and had bushes with a much greater mass of material than the other arm.
As I had ordered shiny new bushes from Mdina I did not keep either set of the old bushes as I seemed to be generating a lot of old worn stuff and don't have much storage - this was a mistake.
So new bushes came and the gap is way too wide for the worn pin that came off. There is a tiny amount of movement using the other pin, is this OK, will it tighten up when I fit in the arm - is some movement needed anyway?
What I should have done is saved the old oversized bushes from the worn pin and got them reamed to fit the less worn pin but once again you live and learn. I spoke to Mdina who do advertise an oversize bush but this is oversize on external diameter which we couldn't see much call for!
Any input welcome
Thanks - Duncan
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Re: swing arm bushes

Postby Steve Brown » 26 Mar 2020 20:12

I think there will be more slop till the bushes are fitted in the swing arm. You can't really specify a clearance for when they are loose as the arm they go into may be slightly different sized by wear or abuse etc. So fit the bushes then check and if needed ream them to suit the better of the pins.
I suppose these bushes will be some made for NLM so tolerances will be down to whoever produced them and how well they followed the orders they got.
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Re: swing arm bushes

Postby 72degrees » 27 Mar 2020 08:19

Steve Brown wrote:I think there will be more slop till the bushes are fitted in the swing arm. You can't really specify a clearance for when they are loose as the arm they go into may be slightly different sized by wear or abuse etc. So fit the bushes then check and if needed ream them to suit the better of the pins.
I suppose these bushes will be some made for NLM so tolerances will be down to whoever produced them and how well they followed the orders they got.

A bit like fitting pressed in small end bushes - they will get 'squeezed'.
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Re: swing arm bushes

Postby dunk 1 » 27 Mar 2020 10:07

They compressed quite a bit - I was quite surprised at how much- they are now a close tolerance on the smaller of the pins - similar to the removed ones and they were fine when fitted so I may fit with that pin and if there are issues get them reamed to the larger one - thanks for input - Duncan
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Re: swing arm bushes

Postby norbert » 27 Mar 2020 23:36

In most cases the problem is a worn spin rather then the bushes. Often it helps to give the spin a 1/4 turn when swingarm clearence appears :wink:
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