Improving shifting on a well beat Mongoose Stat

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Picked this up last year a police auction and thus has unknown history. Got it going pretty well but has some shifting issues... Everything works but bike has a weird noise in 2nd gear and some times skips a tooth or more in top gear.
It's a 7 speed Shimano Tourney TX and twist grip shift. Bike was not expensive and not taken care of, but I llike it and would like to upgrade it. where would you start, shift cable shifter, derailleur. freewheel, chain? :whistle:
 
Chains tend to stretch and freewheel cogs wear quickly if you ride the same cog often , get a new freewheel and chain and adjust the rear derailleur with the barrel adjuster you should be fine a quick inexpensive fix or find a donor bike laying around , I bought a bike last year from a yard sale for $3 , owner said it wouldn't shift , same issue your having fixed no problems and gave it to my buddy who recently had a car accident and needed wheels for work
 
When I first got the bike I used PB Blaster to unstick the chain... http://ratrodbikes.com/forum/index.php?threads/mongoose-stat-back-from-the-brink.98084/
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Have maybe 150 mi on it now, I have applied spray on "liquid wrench" chain lube. I may remove the chain and let it soak in diesel fuel for a while. This is how it looks today...
tourney tx.JPG
 
This is my rear derailleur (Suntour AG-5000 1983) and Maillard France freewheel dated 1983 still working after 33 years and og shimano uniglide MTB chain 3/32x1/2 (date code 3F 1980)
 

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If I do replace the twist grip shifter and rear deraiier I was thinking
Shimano RD-M310 Altus GS 7/8-speed Rear Der Black,Long Cage
or
Shimano Tourney Tx55 6/7-speed Rear Derailleur, Direct-Attach
and
Shimano Altus SL-M310 Rapid Fire Shifter - Right, 7-Speed.
maybe also
Shimano MF-TZ31 Tourney Freewheel (14-34T Mega 7 Speed). I'm gonna have to look in the barn - think I have a small bottle of tri flow around here somewhere. :thumbsup:
 
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Replace the chain at a minimum. On any bike given to me that skips and I want to keep I always replace the chain, free hub and chain wheels. At a minimum I take off the cables and blast out the housing and oil the cables. If they are frayed or rusty I replace them. If the bike has canti or V brakes I remove the brakes and polish and oil the mounts. If they have been sitting outside or ridden in the winter I sometimes have to dismantle the brakes again in 6 months to get them working well again. Twist shifts are good if your are going to ride in cold weather with mitts or lobster claws or have arthritis in your hands. Some new top dollar fat bikes now have twist shifts. Some Shimano front derailleurs are notoriously stiff and become more stiff with age. They need to be removed and placed in a vice and moved in and out by hand while blasting them over several days with first penetrating oil and then brake clean and then Dry Slide. They loosen up but are still stiff. The twist shift that is not indexed but has click stops work great for these as the stiffness will exhaust your thumbs in no time. They are very reasonably priced, much less than a new front derailleur. I have had a few road and mountain bikes where most of the drive line had to be replaced to get them to work right. I have even had to replace derailleurs but if you do this make sure the new ones pull the same way the old ones did. Keep at it and it will work fine.
 
HF....The best advice I can give you is simply replace the cable and housing from the shifter to the derailleur, and it will shift like buttah. I can guarantee it has never been done looking at the kink at the derailleur where the housing comes in. I like to buy bulk shifter cable housing and cables on ebay. It is well worth your while...
 
I pulled the chain and let it soak in a can with diesel fuel for a couple months. Pulled it out and wiped off excess. It is marked TAYA and seems to have plated pins.
Tb50.jpg
Installed chain and it shifts great, still going to change the gear cable as it is frayed.
 
Make sure the chain measures exactly 12" pin to pin. If longer than that, no bueno. Cleaned up good!
 

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