AllWeatherJeff

A screw fell out of the shifter on my mountain bike. Its position is directly adjacent to the where the front derailleur cable and barrel adjuster enter the shifter body.
It still shifts into the small and middle chain rings, but it will not shift into the large chain ring.

Is the missing screw the issue? Can I DIY the repair at home, or is this a repair best left to an expert mechanic?
The bike is a 1997 GT Backwoods, with shimano deore indexed thumb shifters

dedhed

Is there a model # on the shifter? Speeds?

Looking up the model, if the tech docs are available the parts list may describe as - Screw - MX x XXmm

dedhed

Or go to a "good" hardware store and buy some M2/M3 screws in the couple of thread pitches they have and try them until you find the right one. If the other shifter has the same screw, pull that out and take it to the store and match it up.

Looking at this it's probably M3
https://www.sjscycles.co.uk/brake-le...page=6&geoc=US

AllWeatherJeff

No model number, but it's a 3 speed front derailure shifter, for a Shimano Deore mtb front deraileur labeled: Mega 9 Drivetrain.

AllWeatherJeff

The screw you link is for a brake lever assembly. I need the one for the shifter.

The screw I need is smaller. It's counterpart on the rear shifter is a Phillip's head type. I don't want to remove it, in case doing so alters the function of the rear derailleur.

jbucky1

Any good Local Bike shop should just be able to give you a screw for that.

- james
www.buckyrides.com

dedhed

Sorry I grabbed the wrong page. And you have to scroll through things. Somewhere on your lever is the model # something along the lines of ST or SL - MXXX
https://www.sjscycles.co.uk/gear-spa...eoc=US&page=10


It's probably a 2 or 3mm, It's not like Shimano typically uses some one off exotic screw for things like this.

Andrew R Stewart 

[QUOTE=dedhed;21300666]Sorry I grabbed the wrong page. And you have to scroll through things. Somewhere on your lever is the model # something along the lines of ST or SL - MXXX
https://www.sjscycles.co.uk/gear-spa...eoc=US&page=10


It's probably a 2 or 3mm, It's not like Shimano typically uses some one off exotic screw for things like this.[/QUOTE

Some of the tiny screws in there shifters are rather odd with a shoulder portion.

jbucky1 gave the best advice. Take the shifter (bike) to a LBS that does a lot of service. Good chance they have a donner shifter in their scrap box to "steal" a screw from. Andy

dedhed

I get that it might have some sort of interesting shoulder, but there's a reasonable chance that doesn't affect the function of the screw. It'd be worth a try for a 40 cent investment.

Checking the LBS is a good option although around here they don't seem to have or keep a lot of that kind of thing around. If the OP has a bicycle Co op around it would probably be the best source for the screw or a complete shifter at a reasonable price.

WizardOfBoz

I think that this screw may hold the cable end in the shifter. See pic of analogous shifter below. If so, try adjusting the barrel adjust on your shifter to get to the largest chainring.

Also, the site immediately below has a LOT of Deore shifter parts diagrams. You might be able to find your unit. It's in German. Search for Schalthebel Shimano.
https://www.veloruf.de/n/shimanoteile.html?id=658713

Andrew R Stewart 

The missing screw has nothing to do with cable retention. It holds the plastic covers in place. The metal foundation plate has a threaded hole that the cable adjuster fits in. Andy

WizardOfBoz

That's certainly what the pictures on that site seem to show. This may be good news for the OP, an the lack of shifting may simply be the cable getting loose. Check adjustment and cable tightness of the shift cable?

Wilfred Laurier

There might be the identical screw on the other shifter. If you remove it from the R and put it on the F shifter to see if that fixes your shifting problem. I suspect it will not - it is probably just to hold a plastic cover in place. Unless the plastic cover is moving and causing interference, or the screw holds one end of the shift mechanism in place and it is moving inside its housing, then that screw should have no effect on shifting.

ramzilla

Hate to say it but, it might be time to consider new shifters. Check out ebay. Most of the time you can find new Shimano replacement parts with no shipping for about 1/2 price from other sources.

madpogue 

^^^^^ New? over a single cover screw? That's like trading in the Rolls when the ashtray is full.

And is there such a thing as a _new_ Shimano 7-speed shifter? (Probably 7-speed, being a '97.) NOS, maybe, but that usually means NOT cheap.

Since it's a cover screw, matching up a new one based on the one from the rear shifter is a pretty safe bet. There's probably one in a coffee can or mustard jar at a nearby bike co-op (depending on the OP's location).

AllWeatherJeff - can you elaborate on "will not shift into the large chain ring"? What _does_ happen? Looks like this is a trigger (not thumb) shifter. So when you hit the "bigger ring" trigger, what happens? Does the trigger fail to move far enough to move the derailleur? Does the trigger move, but fail to engage anything in the shifter? Does it move, engage, move the derailleur, but fail to "keep" it on the large chainring? Or something else entirely? Knowing what it _does_ (rather than what it doesn't do) will help troubleshoot.