Chain Suck??

FF4540

Hopefully someone can shed some light on this,my ST4 has just started this in the last 2-3 weeks.
When changing from the big ring to the the middle (on the front) occasionally the chain is wrapping upbetwen the chainstay & the chainset (doubling up),damaging the chainstay paint and jamming up the drive.
If i hear or feel it starting to do it I back off & move pedal back 1/4 of a turn and it changes ok,but obviously i'm losing the power doing this

Danlube

Give the chain a good clean, it may be sticking.

Bent tooth?

FF4540

Chain is cleaned & lubed after every offroad ride,I use gt85 to initially lube then use Finishline wet lube,no bent teeth either,may have to remove chain& give more thorough clean.

Is this classed as chain suck?

Skonk

The front mech may not be moving over quite enough, so as the chain drops down to the medium ring the top of the chain hits the mech causing the chain to lean over to the side and the top of the chain gets stuck under one of the pins on the big chain wheel.

It happened on my SX Trail when it was brand new (causing the same damage and problems you described) but once the slack was taken out of the gear cable the problem vanished.

FF4540

Mmm will check that because it seems to have only started since I had the new 2010 swingarm fitted & frame repainted,hopefully will get it sorted before I lose anymore paint :x

Thanks for advice to you both

Tank-slapper

A change of lube might help as well. The 'wet' lubes cause crud to stick to the chain and clog it up. Try a wax based dry lube instead.

MrChuck

Are the rings getting worn? If they're getting a bit hooked they can get a bit reluctant to let the chain go and carry it round up into your jam.