Bicycle Mechanics - Freewheel is becoming a fixed
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I have a BMX bike that has a flip flop hub. Its a freewheel, and it will get stuck and become a fixed gear. I know it not the crank or chain, but the freewheel. I can replace the freewheel pretty easily, but would prefer to fix it. Any suggestions will be greatly appreciated.
07-08-08, 11:58 AM
I've cleaned out bigger regular freewheels by dunking the whole freewheel into a small bucket of paint thinner. The mineral spirits thinner used for regular oil house paint, not the lacquer thinners or other stronger ones.
Wear some oil resistant gloves and work the freewheel while it's submerssed and lift it out often to drain then dunk again working it more and more. If it's dirt in there then it'll feel really crunchy at first and as the stuff is worked out it'll free up and run better. Keep up the dunking and working until it feels pretty good. Drain it and set it aside. Leave the solvent for an hour or two to settle out the crud. Pour off the good stuff into another container and wipe out the crud that settled to the bottom. Pour the solvent back into the small bucket and repeat the dunking and working to get it really well cleaned.
To lube the freewheel following this step I use some thicker chain saw bar lub oil I've got and mix it with a little of the solvent so it's thinner. Then dribble some into the gap and spin the freewheel to send it into all the bearings and ratchets. Use enough to really soak the insides and then set it over a container and let it drip dry for a little while. The solvent will dry away after a couple of days and leave a thin coating of the thicker oil. Just right for this job.
Now if the cleaning doesn't make it nice and fresh feeling then it's likely because of rust or bearing balls that have gone flat from jamming and wearing. That sort of stuff really isn't fixable. But if you can figure out how to get the freewheel apart at least you can see the trouble for yourself and there's sure nothing wrong with some curiosity. It may even be that there IS something you can fix.
To get it apart you'll need a chain whip to hold the one part and some sort of tool to unscrew the other part. This is all rather vague because it's impossible to suggest which tool or how to adapt something to do this without seeing the freewheel.
And of course you need to take the freewheel off the wheel before you can do any of this. So at the very least you need a freewheel tool and some way to turn it strongly enough to get it to crack loose from the wheel hub.
You can't try to clean it while it is on the wheel since whatever you use will go into the wheel bearings and wash out the grease in there and to repack them you'd need to remove the freewheel anyway. So best to just get the darn thing off right away.
A big heavy workbench and a nice strong vise bolted solidly to it works nicely as a way to hold the freehwheel tool. Then put the freewheel onto the splines or teeth and crank on the wheel. Just be sure to hold it down on the tool square and with some pressure to stop it jumping out. If that happens things get ugly in a hurry so be careful.
Thanks for the great response, I will try this and hopefully it works. I have a chain whip and wondered what is was for (I bought a bike tool box and no instructions) and now I understand.
Appreciate your help
07-08-08, 02:06 PM
In this case the chain whip is being suggested for something that it's not really intended for. USUALLY it's for holding cassettes while you loosen the center locking ring. The other uses are just gravy on the fries... :D
07-08-08, 07:43 PM
That's a great long post that can be summed up into 1 easy step
1) Turn bike over on side
2) Flush it with synlube into the crevasses of the freewheel
3) Rotate cranks forward
If that doesn't really work, Freewheels are $10. Save yourself the labour. Seriously.
I ended up replacing the freewheel. When I took it off, you could hear something was loose in there and was by my estimation toast. A new one was only $25 so it wasnt a big deal. Thanks for the help
07-11-08, 05:24 PM
Yeah, stuff rattling around is usually a sign of bad mojo... :D
I'd rip it apart anyway but them I curious about stuff like that. The bits would end up in the garbage anyway if it wasn't something simple to fix.
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