Chain Tensioner Chain tension varies from tight to loose

Discussion in 'Transmission / Drivetrain' started by Max-M, Mar 17, 2012.

  1. Max-M

    Max-M Member

    My chain tension varies from tight to loose as I rotate the rear wheel of my bike. At the tight point, the chain seems a little tighter than the ideal tension, but not excessively. And at the loose point, the chain isn't at the ideal tension either; but again, not excessively loose.

    Should I be concerned about this variation in chain tension?

    And what would be causing this? A less-than-perfect drive sprocket? A fault with the chain?

    I've modified my stock tensioner by replacing its nylon roller with an idler sprocket specifically sized for my #41 chain (pic attached), and the tensioner doesn't move out of position because the chain stays on my bike's frame are oval-shaped. Alignment of the chain seems to be perfect.

    Thanks for any insight you can provide.

    Attached Files:


    TREEWK Member


    It is commom for sprockets to have a high & low tension position. From your one pic, it looks like you have a 4 stroke engine with pullstart and a quenton Q Max tranny and a machined hub/sprocket adapter = all good components.

    A spring tensioner would be excellent if the above info is correct. Add a short arm to your tensioner and move your idler sprocket to the end, add a proper spring anchored to the seat stay above. It will work like a hydralic lifter on a camshaft = self adjusting and easier on the drive chain and sprockets etc.

  3. Max-M

    Max-M Member

    Yes, Ron: Huasheng F142 four-stroke, Q-Matic, machined hub adapter.

    Since putting that hefty idler sprocket on the stock tensioner arm, and seeing how nicely the properly-sized idler sprocket functions (versus the stock nylon roller), I've been thinking about getting that idler sprocket set up with a better, spring-loaded bracket. Your idea sounds sensible; I hadn't considered using the seat stay as a connection point for the spring. That simplifies this design project a lot, and I think it'll look good, too (I'm always considering the esthetics of my amateur engineering projects!).

    Thanks for your input.