New guy with a DH bike

Discussion in 'Friction Drive' started by MikeSpies, Mar 1, 2012.

  1. MikeSpies

    MikeSpies New Member

    I looked through the picture thread and settled into what I think I want to do.

    I think I'm going with a friction drive, chainsaw engine, setup.

    I will probably do all the work myself (machine shop at school).

    It will be rear mounted with a small rack built on top. I want to look into reducing noise by putting some sort of baffled muffler on the exhaust (ideas?) I dug through a chainsaw/friction drive thread and looked at gear ratios a bit.

    At WOT I'm aiming for about 35 mph or less. Any idea about how friction drive bikes climb hills?

    It will have a lever system for engine engagement (prob. spring loaded) and throttle going to the front bars. or should I try to incorporate a centrifical clutch. Do chainsaws come with one?

    I'm aiming to spend less than $80, but I'm not afraid to drop a little more coin.

    Any thoughts on my plans?
    Hit me with some knowledge!!


  2. MikeSpies

    MikeSpies New Member

    I was also trying to decide between 2 & 4 stroke. I know in general 4's have more torque and better mileage and are quieter. 2's are louder, less efficient, but rev well; and cheaper.
  3. wheelbender6

    wheelbender6 Well-Known Member

    Everybody that has a Subaru Robin loves it. Cost more than a 2 stroke, but have a great reputation.
  4. HeadSmess

    HeadSmess Well-Known Member

    4 strokes are awkward to do oil changes on when mounted, so a quick release that works will pay for itself after a few times :)

    but, theyre good on the fuel and quiet, without a huge top end.

    a twostroker can be worked to scream and shred tyres or be docile if wanted...

    19-22mm (3/4-7/8)rollers seem to be the ideal. regardless of wheel size. the wheels just an idler and doesnt affect the final drive reduction.

    hill climbing ability depends on tyre used and how much air it has. how hard the roller presses against the tyre. the engine being used. weather. how many times you visit ronald mcdonald.

    isolating the roller from the engine is the best method so that the roller has its own seperate bearings to take the load. otherwise youll destroy crankshaft and or crank bearings.

    daily rider, dont go friction.
    Last edited: Mar 3, 2012
  5. MikeSpies

    MikeSpies New Member

    I feel like I may want do a 4 stroke chain drive. It will be more of a daily bike, I feel like I would have just switched from a to chain drive within a few weeks anyway.

    I think a 4 stroke would be better for my commute as well. Back to the drawing board...

    Modified hub or clip on wheel for belt drive.

    Chain drive with clutch..
  6. darwin

    darwin Well-Known Member

    OP check out the stanton/kit army bike for sale just posted today.........just saw your budget, still a cool bike.
  7. MikeSpies

    MikeSpies New Member

    On it.
    Last edited: Mar 4, 2012
  8. MikeSpies

    MikeSpies New Member

    Changed my mind again...

    Fixed the speed shift (frayed cable in the hand part of the shifter)
    Purchased some lights and speedo

    Just because of simplicity and cost Im going to go for a 2 stroke friction drive.

    Supporting the engine is going to be tough. There are holes for bolts off the chainstays by the hub. I'll clamp the other part to the upper chainstays.

    The bike is going to happen this week for sure. I'll keep you posted
  9. MikeSpies

    MikeSpies New Member

    I'm having a tough time getting a engine for a decent price...

    Considering do a pulley set up now. How is a 20" rim attached to the spokes? i know its notched, but what holds it there?
  10. MikeSpies

    MikeSpies New Member

    On Friday I picked up a Poulan 42cc saw. Went through it and i think I have it running pretty well now.

    If I do a friction drive I'll have the engine over the gears on the right side.

    If I do a belt drive I'll have the engine hanging way off the left of the back tire.

    I'm not sure what direction I want to go. I have heard that for a daily driver, you don't want to go for a friction drive...
  11. MikeSpies

    MikeSpies New Member

    pictures to come