Using common 410 chain as drive chain with the help of a bump rail

Discussion in 'Transmission / Drivetrain' started by Wolfshoes, Feb 8, 2015.

  1. Wolfshoes

    Wolfshoes Member

    The Grubee 66 engine kit arrived last summer with the new standard 415 chain. I had a problem. The chain rivets hit the rear engine mount bracket causing noise and the chain to jump the rear sprocket. The engine was shimmed as to not need a tensioner. The bigger chain was taking more room to the right and a new style stamped mount bracket was taking more room the left. There were other problems. My rear whitewall was no longer white from the chain rubbing. The fit on the rear sprocket was sloppy requiring more clearance. One way to make clearance was to convert back to 410 chain. Original equipment 410 chain apparently is a custom link height chain that is no longer readily available. I ended up with a pile of common chain sold as original equipment spec motor drive chain. Too late now, make it work.

    Chain traveling around the drive sprocket has always been sensitive to small changes in tension. When the chain gets too loose the drive sprocket teeth can bite down on the sides of the chain link. To prevent this, the link height was increased so the chain would wedge against the housing before the sprocket teeth could damage the chain. The taller link height also made it easier for the chain to engage the rear sprocket. Why the chain was widened from 1/8 to 3/16, I don't know. It may sway sideways slightly less making it a little more forgiving when used without a tensioner. Either chain is more than strong enough to cope with the 27 lbs. of pulling force created by the china girl engine.

    In order to use common single speed bike chain, it needs to survive low tension situations when traveling around the drive sprocket Nothing new; jam first before the sprocket teeth can eat the trailing chain links; or better yet travel through even when loose without damage. I would like to propose a solution that is closer to the better yet.

    One way of doing this takes very little material, cost or time providing you have access to the old spec 410 drive sprockets. Also it is easily undone or redone. 415 drive sprockets can be narrowed into 410 sprockets if need be with a handheld dremel and cutoff wheel by grinding back the inner surface of the teeth. By grinding back in inner surface of the teeth, additional mounting bracket and tire clearance is created. A machine shop grinding machine would be better yet, but my bike is now functioning using the hand grinding method since the 410 replacement sprocket I ordered ended up being the wider 415 version.

    In order to reduce the sensitivity of the chain fit during low tension or rear derailment situations the drive sprocket housing was modified using a piece of 1/2 inch steel banding strap material used in truck shipping pallets and a chalk tube of silicone rubber from Walmart.

    View attachment 56076

    There are no mechanical fasteners. The housing area is cleaned with degreaser (unless it is new motor) A short piece of strap is backfilled with silicone rubber. The chain and or other short pieces of banding strap are added during the curing process to create clearance for the chain. The cover is reinstalled during the overnight curing process. The silicone rubber holds the metal strap in place. This bump rail ( for lack of a better term) could also be helpful when tall link height factory 410 or 415 chain is used but the back surface of the housing may have to be ground back to make additional clearance for the strap.

    The Schwinn Beach Cruiser bike is currently fitted with KMC Z410 Bicycle chain as a motor drive chain. This is a very short link height chain giving it maximum clearance through the sprocket housing. Taller link height 410 Bell Chain should also work with this mod.

    It's winter now, I don't have much riding time on this mod. Consider it a beta mod. needing long term review. Being a short link height chain; the rear sprocket needs the help of a mini wheel sprocket tensioner mid way to reduce chain sway. The nylon tensioner wheel does not appear effective enough at reducing chain side sway.

    A rider resigned to using a frame mounted tensioner and believing every ounce matters may like this mod. A rider happily using factory 410 or 415 chain with or without a tensioner may prefer not to make a change. Take it for what its worth. Happy riding!