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-   -   Bike cranks (http://www.diychatroom.com/f2/bike-cranks-1758/)

dienam3less 01-29-2006 01:11 AM

Bike cranks
 
ok how do i take off a bike crank? i took off the dust cover n took off the nut but it dosent come off. also the bike i am putting the arm on has a threaded in side like a bult goes in but the one i am taking off usees a nut to hold it on. will this become a problem?:confused::confused::confused::confused:

747 01-29-2006 02:12 AM

Are you talking about a motorcycle like a dirt bike and the kick start on it. Actually my father was a partner in a honda dealership when i was growing up. I use to work in the parts dept. If thats what your talking about there shoud be a bolt undo it they you have to pry it off. It probably just won't pull off. Also when installing a new one make sure you thread it properly because it you don't you could strip those threads and then your screwed meaning the threads the kick start goes on. I have seen this before and you would have to then take engine apart and replace that. Sorry i can't be of more assistance to you i'm not sure whats going on with motorcycles these days. I actually use to race motorcross when i was a teenager in the 125 class. Had a honda 125. That was the mid 70s so its been a while. My first motorcycle was a honda qa 50 2 gears than a trail 50 3 gears than a xr 75 four gears first clutch bike. Than a cr 125. Than stopped racing had a honda hawk 400. Then i wen't in another dirrection being airforce.:D

DK75 01-30-2006 04:39 PM

I used to ride mountain bikes for a long time and spent much time taking them apart and putting them back together. If it is this type of bike you are refering to, then it sounds as though you have 3-piece cranks. Basically there is an axel-like hub assembly positioned inside the frame housing. This is sometimes refered to as a "bottom bracket". The cranks typically fit onto the axel-hub. In most cases that I have seen, the cranks have a square connection, while the axel-hub has the equivalent square machined to make them fit together.

Installing them is as simple as fitting the crank over the axel-hub and then screwing on either a bolt or nut, depending on type of crank assembly. Some use a threaded bolt that screws directly into the axel-hub. Others use a nut that screws over the male threads on the axel-hub assembly.

removing the cranks is another story. The tolerances between the square connections (crank to axel-hub) are very tight to the point the crank is actually pressed-fit onto the square shaft. In most cases there is a tool that screws onto the crank into the fine threads used to hold dust cover caps on. Once secured, a lever is turned clockwise to push the tool onto the axel and essentially pull the crank off. This is the same as any bolt-pulley tool, however made to fit bicycle cranks. If you have a wheel puller, you can try to grip the crank from behind and pull off.

If you do try to bang it off with a hammer, I would suggest using a piece of wood to hit on to avoid damaging the cranks. Also beware that if you bang too hard you risk damaging the bottom bracket which is harder to replace and more expensive.

Best of luck.

jmic 01-31-2006 07:27 PM

AWW Shucks , just beat it out with a 12 lb. sledge hammer!:)

pastfast125 02-04-2006 03:51 PM

If the crank is the way I think it is..Then There should be 2 big nuts on there, Real thin, but the size of the whole crank, The first one you sshould be able to loosen off, then the second one I beleive is reverse threaded, so turn it right to loosen it. Then you should be able to get it open. If it is a certain kind of 3 peice crank, then on the end of the crank, at the bottem, so opposite of the pedal, there is an allen head bolt...You'll have to take that out an pull the actual crank leg off before you can get the crank out of the bike. Sry if that was confusing.

dienam3less 02-08-2006 12:42 PM

bike crank
 
no i am talking about a bike like u pedal. i used a pickel fork to get the left side off but on the right side were the sprocets are i cant get ir off. i dont want to bend the sprockets. is there any way to get them off with out bending it? wht about taking the barings out and just pushing the main peace through to the other side? it is a 3 peace crank by the way. thanks


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