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Bicycle Repair/shimano revo sis sifter number does nt diplay correctly

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Question
I have an mtb which i have buy 4 weeks ago it

has a shimano revo sis index sifter (front) the number there does nt display correctly please help me

Answer
Your shifter cable system has "settled in", resulting in lower than ideal cable tension.
To evaluate that condition, it is necessary to position the chain on the drivetrain such that it is placed on the largest/lowest/inner cog on the rear gear cluster; you can do this by pedaling the crank and shifting the rear derailer to the "1" or "L" setting.
Next, we need to put the chain on the Middle chain ring of the crankset; you can do this, like the rear system, by pedaling the crank followed by shifting the left hand  shifter to the "2" or "M" position. The front derailer may not receive enough cable tension from the shifter, but you should be able to use the lever to coax the chain on to the Middle ring.
Follow the front shifter cable system to its entry point on the shifter at the handlebar; there should be a "barrel adjuster" mechanism there which acts as both a cable stop and as a method for adjusting cable system tension.
With the Front shift system shifter set at "2" (or "M"), the front derailer should almost be rubbing against the inside edge of the chain (With the chain positioned on the Middle ring on the front gear cluster and the Lower/inner/largest cog on the rear cluster). Any noticeable gap is an indication of insufficient cable tension.
To add tension to a  cable system involves turning the barrel adjuster mechanism located on the handlebar shifter counter clockwise. This effectively lengthens the cable housing portion of the system, causing the tension of the anchored inner wire to increase. this operation should pull the front derailer more rightward, ideally to the point where it is lighlty touching the inner edge of the chain.
Depending on how much slack has developed in the cable system, there might not be enough space available on the barrel adjuster alone--it only has a reliable range of about 8 complete turns. In that case, you may have to resort to re-attaching the cable at its anchor point on the front derailer.
To do this, reset the Front shifter and derailer to their lowest (or "L" or "1") position, again, by pedaling the crank and shifting the deariler and chain so that the chain ends up on the smallest/lowest/inner chain ring on the crank. Next, reset your front shifter barrel adjuster to the fully clockwise setting. Now, trace the front shifter cable system inner wire to its attchment point on the Front derailer. Loosening the cable anchor bolt at this point will allow any excess cable slack to be now pulled out. Tighten the cable anchor whilst holding the cable taught.
Now you can revisit the first steps to fine tune the system cable tension. Good Luck.  

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James Novak

Expertise

I can answer most inquiries with respect to bicycle assembly, repair, tuning and maintenance. I am less than inclined to speak on such questions as "What kind of bike should I buy?", &/or "What is this bike worth?", etc. Any answers to these types of questions may correlate poorly to an acceptable "fact/sarcasm" ratio.

Experience

7 seasons of "Professional" bicycle service/repair, etc. 4 seasons as Instructor, Professional Bicycle Mechanic training college. n-1 seasons of riding, cracking, crushing, mutilating and breaking bikes of any & all varieties, and thus requiring intense and at-hand skills development, etc.

Education/Credentials
Certified Professional Bicycle Mechanic; Winterborne Bicycle Institute/Conestoga College

Past/Present Clients
The Hub Bicycle Shop, Hespeler Winterborne Bicycle Institute

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