Bent swing arm

[gribley]

After having my frame and swing arm powder coated and fitting new pivot bushes I find out it is bent in the lateral plane.
With the arm fitted the suspension units are out of line by about 9mm top to bottom (bottom out towards the left). With the wheel mounted using standard spacers it is offset to the left also by about 9mm.
If I space the wheel over to the right by 9mm, the wheel is central, aligned correctly with the front and the chain line is correct.
I guess I need a new swing arm but MX4s are rare. My MCS/2 arm is substantially similar in dimensions apart from shock mounts, are other arms suitable? Griffon maybe? it looks the same to a bloke riding galloping horse.
Any one have something suitable? Originality is not important to me
Andy

[Andy Z]

Is it definitely bent? The reason I ask is that in my experience its not uncommon to have shock mounts which don't line up! Or chain-line issues for that matter.

Finding a replacement won't be easy, so if it is bent, repair may be the best option. I'm not 100% sure but I think that design of swinging arms is unique to MX4s, so I don't think a Griffon one would fit, but earlier Challenger ones may fit, although they look different. Hope that makes sense!

Cheers,
Andrew

PS. I do have a spare MDS swinging arm if you're desperate!

[Rob]

Gribley - a bit late since your swinging arm has been powder coated but the old remedy used to be a piece of scaffold pipe between the arms and heave (gently, it doesn't take a lot!)

A lot of swinging arms get bent and I have found it especially on Griffons.

I can probably find a drawing if you need one to check dimensions.

Cheers,

Rob

[gribley]

Rob
A drawing would be very useful

Andrew
I may take you up on the MDS arm

In the meantime I will see how it all pans out with the wheel spaced over. it does give a bit better chain/shock clearance
Cheers
Andy

[Dick F]

Bent swing arm

Hi Gribley,
As our Captain Mainwaring has stated the pole job ia good idea or maybee some stout timber which will give a bit, I remember in the 70s riding at Beenham Park i think , taking a new uncharted line off this rise turning sideways in mid air and crashing rather hard and having a bent swing arm! A Member at the time of the Bognor Regis Club, Bob Spencer a sidecar rider did just like Rob said and it was ok, talking to most riders in Trials and Scrambles most Greeves do bend very easy, My Anglian bent a few years ago and that was twisted back ok.

Thinking back i could ride cambers much better with it in limp mode

[dave higgins]

Robs large pole......

Rob you are a animal.....gribley, the best way out of your situation, is to make a piece of bar to bolt between the swing arm s/mount & the top frame mounting, so the frame & swing arm are solid.
When you do this make sure you bolt the longest side with the bar, as you say it is twisted, one side will be longer than the other, then place a bottle jack between the mounts on the shorter side, & jack it down to match the other side, you will probably have to over bend it as it will spring back to a certain degree, you can also use wood to stop the jack marking the paint.....
This is in my new book.....bodging...the complete guide......

[gribley]

Right I have done a bit more measuring and spacing and then a bit more measuring.
With a 9mm spacer between the arm and the brake plate, a 24mm spacer on the other side, the adjusters on the same notch each side and the spindle tightened.
The wheel is central in the mudgaurd loop, central in the seat tubes and central to the front forks.
I put the gearbox in (no engine so i can run straight edges front to back). The chain line is about 4mm out.
I reckon I will get Jeff to pull the rim over to the right by 4mm, fit a 5mm spacer between brake plate and arm and a 28mm spacer on the right side. That should make everything line up except the suspension units but I can live with that for the moment
Andy

[scott151]

Griffon/mx4

Hi all,

I have put a enduro spec griffon swingarm in my 360 mx4 with no problems.

I also have a spare swingarm if your interested gribley? Just PM me.

Regards

Scott

[Gr11mpy]

Griffon arms do fit MX4's as Scott rightly points out.
Rear wheels on centre line of frame a fallacy on lots of Brit bikes and Harley's due to balancing / off-setting lop sided engine weight.... Oh and on a famous Dunlop winning IOM Honda too.
Cant remember where the rear wheel lines up as standard, Scott will be able to access his bikes to check quicker than I can possibly.
Suspension units should be vertical in an ideal world but again see lots of variance on many bikes.
I've 5 MX4 frames and they all measure up differently on the relevant frame tube lengths, significantly in some cases... Position of suspension mounting points on swing-arms vary to fore to aft on the arms I have.

[brokabolt]

I read somewhere that the rear adjusters arn't neccessarily the same on both sides,especially with snail adjusters. I found this on my griff.

[Andy Z]

Hi all,

I have put a enduro spec griffon swingarm in my 360 mx4 with no problems.

I also have a spare swingarm if your interested gribley? Just PM me.

Regards

Scott

Hi Scott,

A long time ago someone told me that Griffon arms didn't fit Challengers and I foolishly believed them! Thanks for clearing that up!

Cheers,
Andrew

[Rob]

Dave, How could you say such a thing?! Rob you are a animal...

It should be ...... Rob you are an animal...!! Tut, tut!

I'm usually quite fussy about how I do things but Dangerous Dick has taught me a lot just lately and I am now regularly destroying more than he is these days! Only last Sunday, my Anglian would have come off the trailer if I hadn't bothered to lash the wheels to it!

I forgot to add that the wheel should come out first. It's only going to bend again anyway. The only other SA I have known to bend easily is the 250 Crusader trials but the 350 Bullet seems to put up with it OK.

[gribley]

Rob you are a animal.....gribley, the best way out of your situation, is to make a piece of bar to bolt between the swing arm s/mount & the top frame mounting, so the frame & swing arm are solid.
When you do this make sure you bolt the longest side with the bar, as you say it is twisted, one side will be longer than the other, then place a bottle jack between the mounts on the shorter side, & jack it down to match the other side, you will probably have to over bend it as it will spring back to a certain degree, you can also use wood to stop the jack marking the paint.....
This is in my new book.....bodging...the complete guide......

Dave,
it's not twisted its bent laterally, if I put a square on the pivot shaft, the two sides both run to the left at the back

[dave higgins]

In that case,you could use a 4 tonne porta power kit & push the swing arm from corner to corner, but you would have to make a tubed spacer the length of the spindle gap to bolt it up tight, so both legs move over when jacking...
I have straightened them out like that before...elbeit not a greeves one though....have fun..

[gribley]

It's staying bent for the moment. I have spaced the wheel and got everything in line