Chain skipping on new chain and cassette

[alband]

I inherited a (fairly crappy) "Probike Escape" mountain bike and rode it on trails until I broke the freewheel. Since I had to replace the (6 speed) freewheel/cassette, I also replaced the chain and since then, it skips under load, but only on second and third largest rear cogs - every other gear is fine. I can't get it to skip when I flip the bike upside down and pedal with my hands.

I've done a fair amount of forum bashing to try to fix this and here is what I've tried:

• The usual cause of skipping with a new cassette and chain is the front chainring. However, it still skips on all three of the front cogs and because it doesn't skip on any cogs except 2 and 3 on the back, that doesn't seem to fit.
• I wasn't sure if I had put on a chain that was too short, so I put in a few extra links. No difference.
• Another cause of skipping I spotted is the b-screw adjustment on the rear derailleur. This bike's rear derailleur did not have a b-screw, so I replaced it and fiddled with the b-screw a few times but no luck - it still skips on 2 and 3.

Here are some other possible suggestions - good to get some views on these:

• I did wonder if the new cassette/chain/chainring are not compatible in some way, although I did try to buy carefully. I bought a 6/7/8 speed Shimano chain and a 6 speed freewheel
• There is quite a lot of rocking on the rear hub - when the rear wheel goes around you can see the cassette rocking back and forth. I guess I was reluctant to address this because I was trying to avoid rebuilding the hub.

Any other bright ideas?

Thanks,

 

[carvelos]

tight links in chain, worn chainrings, misasjusted rear derailleur... so many things to check... why is your new freewheel so wobbly?

 

[Ajax Bay]

it skips under load, but only on second and third largest rear cogs - every other gear is fine.

• There is quite a lot of rocking on the rear hub - when the rear wheel goes around you can see the cassette rocking back and forth. I guess I was reluctant to address this because I was trying to avoid rebuilding the hub.

When you say 'skip' do you mean it shifts to the adjacent sprocket or that the chain slips (staying on the same sprocket)?
Is your rear axle quick release or nutted?
Is there movement in the axle (bearings)? With the bike standing normally, can you move the top of the wheel left and right by pushing (applying a force horizontally on) the rim with the tyre on the ground?

 

[T4tomo]

the cassette shouldn't be wobbling all over as the wheel rotates. I'm surprised it only skipping on 2 cogs 9probably because 6 spd isnt very sensitive unlike 10spd+ sept ups.

sort the wobbly hub first, then look at fine tuning gears.

I'd err on the side of shorter rather than longer chain (i.e shortest you can get away with that still does bib/ big on front / rear, as too slack a rear derailleur can cause its own problems.

 

[Lauris]

When I replaced my chain and cassete my gears were also skipping.
I used the barrel adjuster to fix the issue, by going into each sprocket and adjusting accordingly.

Hope this helps, and there is a yt from parktool to help you with it.