Our friends son just bought a new school bike and I have given him new tyres, bars,grips,lever,seat and post and got most of it sorted but having problem with the crank. The previous owner put a big f off bolt on with nut catching frame! So need to get new bolt.the small 25t cog is against a big washer and moves up and down, should it have a special washer on the crank that fits into the hole on the cog? Thanks
