Rack-mount, belt-drive, new build

Discussion in 'Rack Mounted Engines' started by knobb490, Aug 16, 2010.

  1. loquin

    loquin Active Member

    You might want to stay on the lookout for a 5/8 inch shaft, belt version centrifugal clutch.

  2. knobb490

    knobb490 Member

    Thanks Lou, great suggestion! Although its quite convenient to compression start the engine with the current setup, that would be a nice addition. Then the rider can keep their hands on the handlebars and not have to throw the clutch lever every time they need to stop and start. And it'd be a smoother transition to powered riding. I'll keep my eyes open.
  3. loquin

    loquin Active Member

    I've seen them for about $50 new, for max-torque clutches. They have a 3.2 inch pulley O.D., which, I believe is a 3 inch pitch for type A (4L) 1/2 inch belts... Occasionally, they pop up on ebay, used, for less.
    Last edited: Nov 3, 2010
  4. Tanaka40

    Tanaka40 Member

    Stainless Steel bomb?

    I hate to be the one with bad news, Is that bottle rated for fuel?? If not, you may want to buy a MSR fuel container that IS rated for carrying flammable liquids. Safety First
  5. knobb490

    knobb490 Member

    Don't think so...

    ...there isn't anything on the bottle stating either way. But I like the idea. Do you know if the MSR bottles ar similar in diameter, such that they'd fit in the drink holder?
  6. loquin

    loquin Active Member

    Yes - the 22 oz MSR bottles fit in water bottle holders.
  7. Tanaka40

    Tanaka40 Member

    I like the 30 oz MSR bottles

    I use to "30 oz" size which actually holds a little more (1 liter)
  8. eastwoodo4

    eastwoodo4 Member

    i can see youve put a lot of thought and work into this bike.

    the only thing i dont like is the weight of the engine and its also to big to be legal and to easy to spot.hows the belt slippage in the rain?
  9. knobb490

    knobb490 Member


    Thanks for checking it out, I appreciate the compliment. Regarding the concerns you raised:

    1) Engine weight - The engine is forward enough on the rack that its mass blends in with my own so I don't notice it much. But that wasn't the case originally (see the post on my blog dated Tuesday, September 14, 2010 called "Building the Rack, Phase 2" http://enginepoweredbikes.blogspot.com/). It's amazing how moving it forward a few inches made such a big difference.

    2) Engine size, legality and visibility - No question that this engine is bigger than a 49cc and more obvious. In the community where I live, I have driven past law enforcement on two occasions. As I approach them, I shut down the engine and simply pedal past them. I don't know if I'm legal or not, or if they care, but I make an effort to use discretion when I know they are around.

    3) Belt slippage in the rain - I'm a fair weather recreational rider so I haven't ridden in the rain. But the belt was slipping even in dry conditions before I put the no-slip tape on the driven pulley. Now it's much better. Would it help in wet conditions? I think so but it's untested.
  10. loquin

    loquin Active Member

    A useful addition for the spare fuel bottle - The UCO Fuel Faucet...


    I've got one, and it works exactly as advertised. Literally, when pouring, you put your finger over the air hole, and fuel flow stops. Lift your finger, and it starts again.

    Attached Files:

    Last edited: Nov 12, 2010
  11. knobb490

    knobb490 Member

    Great suggestion

    How nifty! It's now on my Christmas list!
  12. loquin

    loquin Active Member

    The fuel tank and air filter up on top make the engine look even bigger. I've seen a small engine external diaphram fuel pump that you could use with this engine. You would have to drill/tap a hole in the crankcase, insert a hose nipple, and run a hose to the fuel pump. This way, you could place the tank at or below the engine level, making the engine less conspicuous. Likewise, you should be able to relocate the air filter with some judicious hose usage. Unfortunately, I don't think you'll be able to do anything with that big pull starter sheet metal...
  13. knobb490

    knobb490 Member

    I suppose I could simply remove the pull starter all together since I rarely use it. Most of the time I just throw the clutch lever to engage the belt which then turns the engine over and starts it up. With all those engine elements relocated, the visual bulk of the engine would certainly be reduced. But unless I get hassled from law enforcement, I'm planning to just stay stock for now.
    Last edited: Nov 15, 2010
  14. happycheapskate

    happycheapskate Active Member

    I like your budget-build ULGE motor bike. That is badass!

    I think your speed calculations are off because you forgot to include the tire.

    With the engine mounted or a simulated weight, you can use chalk to mark a driveway, and measure out 1 or 2 rotations of the rear wheel with tire at desired pressure. This will be a truer reading of the wheel circumference in use.
  15. knobb490

    knobb490 Member

    20 inches isn't 20 inches

    I meant to comment about this previously, but forgot. Thanks to Happycheapskate, I'm reminded about it again. I was inspecting the driven pulley (bike rim) attached to my rear wheel and had a tape measure nearby. I decided to measure the diameter of the pulley and learned that my assumption about the bike rim pulley was wrong.

    What I thought was a 20 inch rim is actually 16 inches. It's the outside diameter of the bike tire that's 20 inches. So here I was, thinking I had a 20 inch rim with a drive ratio of about 13:1, when really, I'm at about 10.5:1 That's probably part of the reason I'm so far above off my original goal of 20 mph top speed. Other parts of the reason may be that the engine is running faster than 3600 rpm, and Happycheapskates comment about the 26" wheels.

    I'm going to take his suggestion to measure actual distance of one or two rotations on the 26" wheels and see how it all comes out.

    By the way, does ULGE stand for Utility, Lawn, Garden Equipment?
    Last edited: Nov 18, 2010
  16. happycheapskate

    happycheapskate Active Member

    Yes, that is what I meant, Utility Lawn and Garden engine, as compared to automotive or motorcycle engines.
    There are lots of home built road legal full size motorcycles that use large lawn tractor or generator engines. Check your local laws.

    Street motorcycle with hydrogen generator

    1972 motorcycle with air cooled diesel generator engine swap
  17. knobb490

    knobb490 Member

    It's been a few years, but I recently made some changes to my belt drive bike. Loquin suggested a centrifugal clutch, but I couldn't find one with the pulley dimensions I needed so I built my own using a comet clutch from Amazon to start with. I found that snap rings on the clutch allowed me to remove the sprocket from the bell. I then purchased a cast iron 1.5" pulley from eBay and tack welded it to the bell housing with both the bell and the pulley on a 5/8" shaft to keep them in alignment during the tack welding. In operation, to reduce strain and heat build up on the clutch, I start off under pedal power, then spool up the engine to engage the clutch while I'm already moving. I've only put 20 miles on it, but it's working great so far. I like the simplicity the centrifugal clutch brings to riding.