Hitchcocks Forum

Hello all,
My bike has a new alloy and brass speedo drive fitted. It has not actually been ridden yet as the previous owner fitted it and never took it out for a spin and I am tidying up the bike prior to an MOT.
My issue is that when I spin the front wheel I hear a fairly loud clicking noise from the speedo drive. I have removed it to see if I can diagnose the problem. I can see that the two small lugs that mate with cut-outs on the front wheel move freely but at some point resistance is felt and hence the clicking noise. When it's back on the wheel I have made sure the lugs line up but it still does this. For what it is worth the speedo drive unit does spin where the cable fits in.
Does anyone else have this problem? Or is it just usual? I remember my old plastic drive unit never did this.
Thanks,
Alan

Hi rado. Sometimes the built in spacer of the rotating inner part of the speedo drive gear box can vary and when the nut is tightened to hold it in position, can exert a side force on the rotating ring and squash it into the drive box. Do a very careful close inspection or measurment of thicknesses of the old and new to compare. You might require a thin shim added to the centre boss to gain extra clearance...also can you hear any clicking when the gearbox is operated in the hand of the bike?....just some thoughts.

Blimey! ...just re read my original post I knocked out quickly before dinner...so I had better correct it (if possible)............................... Sometimes the built in spacer of the inner part of the speedo drive gear box that the spindle passes through can vary in thickness and when the nut is tightened to hold it in position, if too thin can allow a side force on the rotating ring that squashes it into the drive box. Do a very careful close inspection or measurment of thicknesses of the old and new to compare. You might require a thin shim added to the centre boss to provide some extra clearance and free up the rotation. Can you hear any clicking when the gearbox is operated in the hand when removed off the bike?

Hello Les,
Many thanks for the reply. I see what you mean.
Tonight I will look and see if that is the case with my drive unit. I'll let you know what I find.regards,
Alan

Hello Les,
I have been looking at the speedo drive today. I think the speedo drive collar that is attached to the front spindle is the problem. I think it is sitting too proud and above the collar on the front hub with the two cut-outs that mate with the drive unit (that the cable mounts to). Being too high it does not let the drive unit butt against the hub but leaves a gap of around 1 - 1.5mm around the unit and wheel. In fact once the hub nut for the spindle is tightned against the drive unit it pushes it to one side and the gap becomes un-even.
Is it possible to use a large socket and a soft hammer to force the speedo drive collar further onto the spindle?
regards,
Alan

Hi Alan.. It's a touch difficult to understand the problem (Its not your fault,it's always hard to put a problem like this into words) As far as I can make out it seems that the drive boss that fits flush with the wheel in your opinion is sticking out too much? The drive ring on the speedo box should have a clearance of about the amount you describe. It would seem to me you need a shim to fit on the outside of the drive boss to keep the speedo box spaced out just a fraction more...with the shim/spacer there will be no pressure on the rotating speedo drive ring. The large nut will still tighten the speedo box securely. The other thing you mention is that when tightening the speedo box cants over to one side...this can only happen I would say if the diameter of the drive boss is too wide to go all the way into the speedo box, so if this is the problem the speedo box has an insufficient inner diameter (not spindle diameter)...so it is either not suitable or the drive boss has to be reduced in diameter. Measure both with an accurate vernier/micrometer. If what I say does not relate and make sense to you, it is because the problem has not been understood correctly by me, but there is very little to get right with the speedo drive apart from making sure it is spaced out correctly. I'm quite happy to stick with this one if you want to come back on it again until we sort it. Oh yes don't bash anything inwards, it shouldn't need that.

Hi Les,
I get everything you write no problems.
A little video on Youtube would demonstrate much better than my writings.
I will look in my bits n bobs box and see if I can find some sort of "shim". Perhaps a thin washer would work?
We'll see!
Thanks a lot Les.
regards,
Alan

Hi Rado, I had exactly the same problems, I also found that, with the nut fitted, the whole wheel/ speedo drive assembly was fractionally too wide to fit in the forks properly unless I tightened the nut so far the drive wouldn't move. I tried different combinations of shims etc but couldn't get anything to work. If you find something that works I'd be interested as I just left the nut off and it seems to be working fine but I'd rather have it with the nut on.