Kalkhoff Agattu peculiarity ...

[danfoto]

I have a Kalkhoff Agattu bought new in February 2012, which has done something over 2500 miles, quite a few of them with a trailer full of shopping. Apart from the necessity to change the chain and chainwheel last year, I've had no problems. However ...

In the last week or so, it's started making a noise which I can only describe as a sort of creaky "clack" which is apparently coming from somewhere around the motor drive. The noise occurs when I first apply significant pressure to the pedals after every gearchange, and it's either one, two or three "clacks". Once it's made the noise(s), that's it until after the next change up - unless I ease the pressure on the pedals. When I do that, I get a quieter version of the same noise - and funnily enough, the same number of distinct sounds!

In other words, it seems that loading the cranks causes something to move/compress/slip or whatever and removing the load allows whatever's moved/compressed/slipped to return to its normal state. If I apply just the minimum amount of pressure to the pedals after each change, it stays quiet, but in normal riding I'm getting this pretty much all the time now - particularly in the lower gears.

Any clues please guys?

 

[RobF]

My guess is the chain is jumping, probably on the rear sprocket.

 

[oldtom]

In my experience, the motor mounting bolts need to be loosened, the motor wiggled around a little, then a re-tightening of the bolts is worth doing before you delve any deeper.

Tom

 

[flecc]

Yes, the three mounting bolts of the unit are the most likely source of the problem, they need to be very tight.
.

 

[danfoto]

Cheers chaps. I'll check out the motor mounting screws later today weather permitting and report back

 

[danfoto]

Hmmm ... well, I'm a bit pushed for time today so all I could get done is establish that the front two motor mounting bolts are as tight as the proverbial but the back one was maybe half a turn off tight. All three are now tight, and by "tight" I mean hold a 10" o/e spanner on the nut and lean on a the end of a very good quality long-series Allen key until it starts to bend.

This hasn't cured the problem but it's definitely made a difference. It needs more pedal pressure to make the noise, and now it only makes the noise once or twice on each occasion the pedals are loaded, and once when pressure is eased off.

So to my way of thinking the next step will be to do as Tom suggested and slacken off all three, wiggle the motor and then re-tighten - unless of course there's anything else I can usefully check or do while I'm furtling about in that area?

 

[flecc]

I think that will do the trick. The trouble is that the unit is mounted into a painted frame, so over time with the pedal forces imposed the units starts to shift inside the mountings as the paint gets compressed, Reseating it and retightening should be all that's needed. The bolts really do need to be tight, the makers recommendation is a ridiculously high 40Nm which is near to stripping the bolt threads.

The other main source of such creaking is the bicycle one of the crank arms moving on the square taper of the pedalshaft and I've known that on these units. However that's one creak per down thrust usually just on one side so easy to identify.
.

 

[danfoto]

Cheers flecc. I could rule out the crank to shaft joint from the start - both sides have copper grease on the mating faces

Will do the business with the wiggling when time permits and report back!

And hell's bells! I've just checked - 40Nm is nigh on 30ft lb!

 

[danfoto]

Well, this afternoon I slackened off all three, did the magic wiggling, then re-tightened them to silly tight. That's 90% cured the problem, and at least I now know for sure that the remaining odd creak or two every now and then is nothing to worry about.

Whilst at it, I was trying to work out a way of preventing any movement at all of the motor relative to the frame, but I can't see one that doesn't involve an amount of buggering about out of all proportion to the problem, so for now I'm going to leave it like it is.

If it comes back, I'll try again once I've got hold of three new Allen bolts and nuts just in case I overdo it with the tightening. Might even oil the thread lightly too