Derestricting Sirocco CDL

[Warwick]

Well, as I mentioned upthread, the chain is new, as is the cassette. The derailleur is adjusted and the chainring seems fine. It's only done 1100 miles, after all. Hence the mystery.

I reckon a chain length of 126 links, as supplied by Woosh was significantly too long. Too long a chain can cause slip. I reckon 118 links might be more appropriate.

Strangely, the slip was in the lower gears, where I'd expect the chain to be more tensioned.

 

[trex]

...
I reckon a chain length of 126 links, as supplied by Woosh was significantly too long. Too long a chain can cause slip. I reckon 118 links might be more appropriate.

Strangely, the slip was in the lower gears, where I'd expect the chain to be more tensioned.

that may be, but I find it difficult to believe it's the case. Woosh sell a lot of CD bikes and they all have the same chain. No other member has reported this problem until now. You said you replaced the chain and the cassette. The chain woosh use is KMC X series for 7-8 speed. The freewheel on the Sirocco CDL is Shimano TZ21 7-speed Megarange IIRC.
http://kmcchain.us/chaintype/x-series-8-speed/
Which chain and cassette did you replace them with?
can you also post a picture of your chain when it's on the largest cog?

 

[Warwick]

Right. At the weekend I replaced the chain (again) with a Clarks Shimano-compatible one. As well, I replaced the derailleur with a straight swap. There was no damage from last Monday's incident.

Well, the chain slip is still there, rather annoyingly. I'm in gear one or two, with no undue noises coming from the transmission and when I come to put extra force into the pedals with my legs (e.g. at a busy road junction) the chain jumps and there is no drive. That is rather sub-optimal, to put it mildly. It also makes a very unhealthy noise and can't be doing the parts involved any good at all. The new cassette is a seven-speed shimano with roughly the same ratios as before. Certainly the upper & lower sprockets are the same as the freewheel. It's not a Megarange, AFAIK. The largest sprocket is 28-teeth.

I will try to photograph the set up, as requested above (assuming I can get some light to shine on it), but I need to reiterate that the transmission did this before I replaced the wheels/cassette hub (it no longer has a freewheel)/chain & derailleur.

 

[trex]

can you put the chain on gear 4 and check the chainline. It should be more or less parallel to the bike's middle line.