Kalkhoff Agattu chain tensioner thingy

[danfoto]

Got myself a s/h 2010 Agattu earlier this week and am gradually getting to know it. One thing I'm puzzled about though is the chain tensioner. How much tensioning should it be doing?

Or to put it another way, roughly how much play should there be on the bottom run with the bike at rest with power off and rear brake on, and light foot pressure on the pedal?

Cheers

 

[flecc]

Is this one of the models with a rear tensioning arm or is it the idler arm on the motor unit that you mean?

 

[danfoto]

Sorry - I'm on about the thingy with the plastic derailleur sprocket on it which lives near the motor sprocket. The chap I bought it off referred to it as the chain tensioner and I haven't yet had the chainguard off for a nosey at it.

If that's the idler arm, my question now becomes what is the purpose of the idler arm and does it have any effect upon chain tension?

 

[lectureral]

I think its main job is to keep the chain on the motor sprocket. I had the same for a couple of years and had a problem at the beginning with it going loose but once I sorted it I never had to look at it again. Unless the chain is jumping on the motor sprocket I would leave it.

 

[tillson]

From the centre of the idler arm sprocket to the centre of the drive sprocket, there should be a span of 60mm as indicated here thanks to the hard work of flecc in preparing his pages of information about this unit.

My chain isn't adjusted to this dimension (much more slack) and I haven't had any problems for thousands of miles. If you want your bike spot on, the above is how it should be.

 

[danfoto]

Hey, thank you gentlemen. The reason for my concern is simply a very floppy chain (a good 40mm or so slack in the middle of the bottom run) and a tendency for the chain to jump what feels like one tooth if I fluff a change down whilst climbing a steep hill.

Looks like it's time for a new chain then ...

Dan

 

[flecc]

You may find things much worse if you add a new chain to the worn sprockets, the new chain jumping all the time on the worn sprockets. It's best to do one of two things:

1) Just adjust the chain by shifting the back wheel a little, readjusting the brake pad alignment if necessary.

2) Fit a new chain, new rear sprocket and new motor sprocket. If quite worn, sometimes a chainwheel needs to be changed too.

 

[danfoto]

You may find things much worse if you add a new chain to the worn sprockets

Yep, been there and done that with an old Dawes. The wheel's already back as far as it goes, so I need to have a really good look at all 3 sprockets ...

Is anywhere in particular reckoned to be good for mail-order Agattu bits?

Thanks

Dan

 

[flecc]

50cycles have all the available spares. Make sure you specify the number of teeth if ordering a motor sprocket or chainwheel, there have been different versions on various age Agattus. As well as from them, the Shimano hub gear sprocket can also come from any bike dealer or online bike store.

 

[danfoto]

Thank you very much indeed for your help.

Dan