So I installed my new chain and it was working fine for an hour. After that the chain started skipping on the 1st gear, but worked perfectly on the 2nd gear.

When I got home, I fiddled around with it for a while, turning screws almost randomly in an effort to solve the problem. I had reinstalled my old 8-speed chain which worked perfectly before, but by then I realized the chain would get stuck fast on the first gear.



The pic highlights the exact position the chain (on the outer cog) would be stuck such that I couldn't turn my crank at all. It takes a fair amount of effort to yank out the chain from between the chain tensioner and cog. Apparently the width between the chain tensioner and cog have been narrowed by my investigative tinkering.

My question is thus: What do I need to screw to widen the space between the chain tensioner and cogs? Thanks for any advice.

Brompton has a set of service documents online and an email question option , they do answer in a few days ..

I only have owned the 3 speed bikes not a 2/6 speed.. yea, may have left a spacer off the axle in your bodging excursions.

The tensioner pulley that is fixed, ie not the one on the swing arm, can that move sideways freely? Take the chain off and see if the fixed pulley has sideways freedom. Maybe take the whole tensioner off and see if you have mounted it with some misalignment on the rear swingarm frame.

Thanks... I will look into it.

It never quite crossed my mind to ask Brompton directly for some reason... guess I'll give them a try.

in the jockey pulley near the cog you will see a derailer like stuff connected to the shifters. i guess your problem is you have adjusted the tension of the cable too loose so when the shifter gone to lower pulley it overshoots.

if this is correct, then you might want to check the spacers, but AFAIK the spacers normally goes outside, inside is the axle and the bolt. so this might not be the case.

i will take a picture of the part on my brompton when i got home to show you what i mean.