Mod chain: tight, loose, tight, loose, tight, loose,

[Patrick]

I'm trying to find out why I can't keep the chain on my mod tight. The tensioners work fine (redline), but as I roll the bike forward or backward (half a revolution of cranks) the chain gets really really loose. Then if I roll it another half revolution, it becomes tight again.

If I tighten the chain while it's on the loose side, then the chain becomes way too tight after a half revolution.

I've asked a couple other mod riders, but nobody can give me a good answer… I'm using a WI freewheel which has only been used 10-12 rides. Is it possible the cog on the back is a bit mashed up? Tks in advance for the help.. I hate floppy chains.

[felix]

Probably your freewheel runs out of true.
If you watch the chain while spinning the cranks backwards you can see at many bikes, that the chain varies it's tension.

I guess this is problem occurs if the threads on the cranks are not exactly perpendicular to the bb spindle.
All my ffw cranks showed this phenomen, some only a little bit, some very much as your crank.
Unfortunately I don't have a solution for your problem.
Just try to find a compromise between loose and tight.
Btw, what cranks do you run?

[WhiteRavenKS]

yes, something is way off in your drivetrain. either your bb is bent, your crank threads are way off or your cog in the back is somehow eccentric tot he axle. this is weird as turds though, ive never heard of this in trials before. i would check your bb, i have seen single speeders with bent bb's where this is an issue.

[chronic]

It happens with most single speed bikes...It's just due to minor imperfections in your cranks. They're not 100% centered to your bb. Your bb could be bent, but I would bet money on it just being your cranks, It happens with most cheap cranks (not to say yours are crap or anything) But I guess it can happen with others as well. Really all you can do, is tighten your chain on the tight "stroke" of your cranks so your chain has enough slack to move freely...

[AgrAde]

my stock does that too with my echo ff cranks, as does my mates bmx.
if it's not overly bad i wouldn't worry about it.

if it's loose enough to piss you off, rig up some ghetto stretchy tensioner?

[BenR]

My mod is like that too because my bb is bent.

[AgrAde]

here's how bad mine is, fault wholly from the echo cranks.

[Patrick]

I'm running Echo supa cranks.. brand new. Also running a new BB, new chain, and new FW, so I'm guessing nothing is bent. The only thing with any wear on it would be the cog that came on the rear wheel (given to me from a friend). this is really weird.

[WhiteRavenKS]

echo supa cranks? brand new you say? there is your problem. some of them come fresh off the factory floor threaded crooked. echo makes good stuff for the money but the tollerences on their parts are not always the highest in the bike industry. sucks but it looks like finding a happy middle ground with the tension is your best bet.

[Darren]

I am having the exact same problem man, when I look at my front track cog, it goes back an forth a bit , so I am assuming it is bent. I am going to buy a new one and see if that fixes the problem. I'll let you know what happens.

[AgrAde]

I am having the exact same problem man, when I look at my front track cog, it goes back an forth a bit , so I am assuming it is bent. I am going to buy a new one and see if that fixes the problem. I'll let you know what happens.

havn't you read anything in this thread?

[Darren]

actually no I must have just missed Kevins last poste. I dont have the money for new cranks/bb so I will have to put up with the problem for now.