Primary drive - judder on transmission

[MARK.WALSH]

A few months ago I noticed on my square 4 that the primary drive had a lot of slop in the mechanism and changing gear on the move was harsh
On taking off the primary cover I found the old transmission spring on the crankshaft had snapped in two.
Drags sent me replacement which I fitted, but I now notice a very jerky juddering on pulling off
Is there a way to fit these incorrectly or is the tension too tight and not allowing enough give on the cams/ spring to give a smooth take off?
Apart from that its fine but it spoils what is a good ride
Cheers
Mark

[john.bebb]

Mark - plz - having discovered your broken shaft shock absorber spring - I assume you checked the mating surfaces of the shock absorber ramps?
I suggest you view this thread http://forum.arielownersmcc.com/viewt ... f=4&t=7018 where Doug is seeking advice on an exceeingly knackered shock absorber on his 350...

I s'pose it's feasible that you have received a "wrong" replacement spring(?) - as a free standing the item (for Mk 1 & 11 Sq4 '49 thru '54) should be 1.5" uncompressed... and you should have to put CONSIDERABLE effort to compress it, even slightly, by hand.

Drags quote a different spring for the earlier 4G and also for the post '54 Mk 11 (I have no details of the variance).

I'm not aware of any tensioning for these parts- assembly is sprocket, sliding member, spring, retaining cup washer, castellated nut... tighten to torque & fit split pin.

Standard "silly" questions: - are both chains properly tensioned (with several checks at different rotations)?... are the chains & spockets all in acceptable condition? - (no links binding?)... were the cluch spring pressures suitably balanced for lift on the refit?... & assuming the vehicle was driven for a while whilst the shock absorber spring was broken... is the outer driveside main crank bearing still intact? ...perhaps the gearbox or clutch bearings require closer inspection... - yes, I know.... silly! but we all may occasionally forget!!!

HTH, cheers,
John

[MARK.WALSH]

John
thanks for the advice I think I will have to do a thorough recheck if the problem persists

On observation on the reassembly of the bike, the cam faces were good and the spring was supplied from drags - so hopefully it is the right one. The only known backlash in the system I am aware of is the worn splines on the crankshaft (most Ariel square 4s seem to have this I think )
Ariel's are a pain in so much as having to remove all the clutch locknuts to take off the whole clutch just to get to the primary chain - I suppose its possible I could have made an error on reassembly but I will check out all you have mentioned

Thanks for the reply - something to keep me busy over the weekend
Mark

[john.bebb]

Hi - Mark - yw - please - I'm not sure what Sq4 you have - note that there are x3 different springs - depending on age... it is feasible that the wrong one arrived from Drags... the little info I quoted covers ONLY '49 thru '54.
It is highly unlikely that "worn splines" should cause judder...
Hope you find the real cause!
Cheers, John

[Brian.Fosh]

Hi
Only for info, The later shock absorber protects the splines with a splined sleeve and fits earlier crankshafts. I recall drags website explains the interchangeability.

I'm using an early rear crankshaft from an iron 4G, as yours with a lock-washer flat, on my '51 mk1 but use the later splined sleeve and shock assembly to protect the crank splines from wearing.

The earlier nut is larger A/F and its corners register within the cup that bears on the spring, but the castellated nut is smaller A/F, deeper and has a turned register on its rear that sits within I/D of the hole in the cup. After tightening up, I chose a place to drill through for a split pin that was away from the flat.

Regards,

Brian

[MARK.WALSH]

Chaps
thanks again for the advice
My model is a 51 square 4, but its reassuring to hear that the problem isn't likely to be the engine splines. I might try and balance the clutch first as that is a quick and easy check. One other problem I do have is a badly worn bearing on the clutch arm fulcrum on the BA box. I did order a bearing from drags.....still waiting. I suppose this could aggravate the problem, but I wont know until the part arrives (with all the other stuff on back order)

thanks again
Mark