Gear indexing

mtbhenry888

I'm fixing a mate's bike, he's got a shimano screw on 7 speed block on a claud butler trail ridge cheapo £200 MTB. The old rear mech is kanckered after 4 years of abuse, i told him to buy a new one so he bought a 2007 (non shadow) LX rear mech for 9 speed. This should work on his current drivetrain but i have a problem, it shifts beutifully through 6 of the gears but when it gets to the biggest sprocket, ie. 1 it just will not shift up, ive adjusted the L limit screw and it makes no difference, i can't understand why it wont shift up to gear 1, its almost as if the mech cant move any further, can anyone help me with this problem?

Thanks!

supersonic

Can you physically move it by hand? Enough cable tension? Try pulling on an exposed piece of cable to tension it and see if it moves then.

Also check the B tension screw that winds in or out the jockey wheel from the cogs (vertically).

mtbhenry888

i can just, it takes quite a bit of force to push it onto the top cog but if i make the cable tension tighter then it cocks up the indexing, i can't win

I tell you what mate, thinking about it i think you could have sloved it, maybe the jockey wheels are too high to clear the cog, i might need to move them down, do i adjust the B screw with cable tension or without the cable in?

supersonic

Usually the best thing to do is to start from scratch! Ensure all the cales run freely and are routed and clamped correctly. Set the H stop with no cable tension and work from there.

What shifter is it?

mtbhenry888

thats what ive done just got it brand new from Merlin cycles, set up limit screws, its a crappy shimano 7 speed budget integrated brake lever 'rapidfire' shifter

supersonic

Just seen you Q on the wheels, yep, wind in the B tension screw - it will move the wheels away form the cogs. Doesn't matter about the cable.

mtbhenry888

Cool, thanks a bunch, youre a life saver, i felt horrible after a couldn't fix it for my friend, it out a lot of pressure on you when youre working on someone elses bike and they have just shelled out on new componnents! :?