Chain slipping in only one gear - chain swapped still an issue

[NATURAL ANKLING]

Hi,
Every thing you describe sounds like a good chain on worn cassette.
Put the chain on the middle sprocket on the front and say the second smallest one on the rear.
Place The bike against the wall, Chain side out, and see if you can elevate the rear wheel on a step or a box crate et cetera, hold the rack with your left hand whilst crouching down, rotate pedals smoothly backwards.
Look carefully at the derailleur and see if you turn pedals backwards at normal pedalling speed and faster, whether there is a jump in the chain or chain link not straightening coming off derailleur?
This would indicate a stiff link and would rule out that problem.
Stiff links will jump more likely on the smallest two sprockets because the chain has to go around a tighter angle than the other larger sprockets.
Chain suck at the front end, that's inability to or difficulty in changing gear on the front chain wheels, can be badly worn chain, and or worn chain wheels (less likely), And even a bent front derailleur.
Chain slippage on rear end normally means a new chain or good chain on worn rear cassette, Especially noticeable on the small sprockets top and second from top gear.
Looking at the gauge no way that's a badly worn chain.
How many miles have you done since new rear cassette?
If you favour these top gears like I do then they will wear Quickly.
but I wouldn't expect them to wear that much on one chain only, My cassette normally takes several not so good part worn chains (0.5-1.0 %) before these small rear sprockets wear and can no longer be used.
Does the chain change onto the smallest rear cog Easily, in other words are you having problems in gear selection on the last two cogs, if so sounds a bit like the rear derailleurs is not adjusted correctly, i.e. cable (stiff) and high gear stop on the rear derailleur needs looking at.
Poor chain alignment on the smallest sprockets normally shows up with unintentional and poor gear changes without any rider input.
If you haven't got any stiff links then it sounds a bit like someone needs to look at the gear selection rear end.
I see you've only done 200 miles? That's not many miles to wear the cassette at all, unless you had no oil on the chain what so ever!
Last thing try the gauge all the way around the chain say every few inches or so?
Without knowing you have Stiff links And let's say you have some stiff links, Normally manifests itself With intermittent jumping and poor selection what seems like poor selection on the last two small cogs.
In this case swapping all the parts apart from the chain has no effect whatsoever on the poor gear selection and occasional skipping of chain.
I say occasional but if your chain is jumping as soon as you apply pressure on the smallest or and the second smallest, this is still a worn on cassette on these two cogs.
I am just thinking whether or not when your cassette was changed is it actually brand-new?
This seems to be the only logical conclusion.

[Pebble]

...I have a box full of unused smallest from 7 speed, I think they would fit an 8 speed (@Brucey) PM me your address and I will post you one. (I am a big environmentalist and hate seeing waste)

thanks for the offer; however I've probably got sufficient already, since my habit is to shorten cassettes, typically by by deleting the smallest sprocket.

cheers

The offer was to the OP, (although you or anyone else would be more than welcome too) The reason for paging you was to ask if the end sprocket for a 7 speed would be compatible with an 8 speed, I'm thinking they are slightly different in how they are spaced. Which is unlike all the other sprockets on 7s and 8s which I have found to be interchangeable as it is the spacers that are diff thicknesses.

Your post has me thinking though, can you actually delete the smallest cog ? it has the indentations for the lock ring?

[squeaker]

the chainrings might well be worn on the OP's bike but that doesn't explain why the chain skips/slips only on one or two sprockets, does it?

OP said:

..if I am in the second smallest cog at the back and the small or middle one at the front..

ie lowest chain tension?

[Brucey]

highest chain tension on smaller chainrings, surely...?

cheers

[NATURAL ANKLING]

Hi,
Have the very same problem on my (both) skip trainers I have put on two newish used chains and replaced the crank sets too.
I normally live with the jumping top cog (smallest) for a few or more rides which can be 70 - 100 miles, after several chains like this the top two cogs get worn and it the slipping is more pronounced, seeking through my used cassettes for some not so worn top cogs.
Last ride I could stand up on big wheel seventh but not sitting 8th, but mid wheel 7th & 8th sitting slipped.
There is only so much time I spend without top gear as its my favoured on the flat ...100".

[GeekDadZoid]

Ok I have spent some time following some of the tips above running on the new chain which is a couple of links shorted than the old one. I found that( as said by a few people above ) that the chain was catching the chain above once per rotation causing the sensation of slipping. Obviously once per rotation of the second smallest cog is quite alot. I have spend a fair bit of time dialing them in and 90% of the time it does not happen, but it does occasionally still happen, could this be frame flex? It is an aluminium frame.

[NATURAL ANKLING]

HI,

Ok I have spent some time following some of the tips above running on the new chain which is a couple of links shorted than the old one. I found that( as said by a few people above ) that the chain was catching the chain above once per rotation causing the sensation of slipping. Obviously once per rotation of the second smallest cog is quite alot. I have spend a fair bit of time dialing them in and 90% of the time it does not happen, but it does occasionally still happen, could this be frame flex? It is an aluminium frame.

1)"chain was catching the chain above once per rotation"....?
You need to expand on that one, is this happening at derailleur rear?

2)"once per rotation of the second smallest cog is quite alot"...?

Maybe a photo of the set up preferably with chain on small front and small back so we can tell if the chain is just too slack?

[squeaker]

highest chain tension on smaller chainrings, surely...?

cheers

Er: oops: meant lowest chain tension on the return (‘slack’) side