4stroke, tank frame, chopper, w/ long write up.

Discussion in 'Photos & Bicycle Builds' started by KeepOnKeepnOn, Dec 14, 2008.

  1. INTRO
    Well, here is my beast. I am not sure whether to call it the "Neighborhood Bully" because it just looks like the kind of bike that punk would ride (thank God he didn't have a motor) or the "Death Machine" from the movie Animal House. I must say that I ended up sinking WAY more time and money into this fun "little" project than I planned, but it was still fun.
    My theme obviously was the old school chopper style. The other priorities were for it to be super quiet and have a frame tank. So I scored a used bike that had a suitable frame, the sissy bar seat, really nice pedals, nice stem, chopper forks, ape hanger handle bars and nice bright red rims for the gasser look with top of the line tires (highly recommended)... all for $100, stoked! For the sake of quiet operation I went for a 4 stroke engine kit, not bad at $240 (Also I hate mixing 2 stroke oil). Then came the unforeseen costs!

    While waiting for my engine kit to come in the mail I decided that increased braking power was mandatory (the primary problem with the cruiser platform). So I welded a piece of angle iron onto the forks and installed a U brake ($). Those nice red rims I had were painted though, no braking surface, so I had to get a new front wheel ($). Last time I had a U brake was my BMX bike in 8th grade. Well I remembered that U brakes weren't to great but now I have been reminded, they are junk. It is better than nothing but still, I recommend against this mod, even though it was cheap and easy. I may weld on some posts for a V brake.
    As it turned out the coaster brake in the rear wheel was shot and I didn't like the one red wheel, one silver wheel look so a new one was in order ($). Overall the thing I am least happy with on the bike is the braking (and the gear box, we'll get to that later).

    The frame tank was a pain but I am happy with it. I grinded a large hole so I could fill her up right at the gas station with the pump. The cap is an automotive oil filler cap ($) with a rubber compression plug. After some grinding to the inside threads, this fit well in a 1.5 inch pipe. I hoped there was still enough thread left to provide a pressure release and prevent vapor locking but there is not, I will have to drill a hole in the cap. To seal the frame I had to plug holes at the steer tube and seat tube. This was done using JB weld from the outside which did not work and made a huge wreaking gas mess (the reason I avoided having to mix 2 stroke oil in the first place). I then poured a larger quantity of liquid epoxy (for surfboards) through the gas filler hole and sealed first the head tube, then the seat tube. I tested the epoxy in gas and it didn't soften and it has held up so far. The tube holds about ΒΌ gallon of useable gas not a lot but if these things really get 150mph it should be sufficient. I will also be adding a water bottle holder for reserve gas.
    I drilled a hole and tapped it for the gas shut off. This only held up for one ride, the steel was just too thin and it stripped out. So I welded a nut over the hole and screwed the gas valve into that...bullet proof.
    The "bent for increased width" cranks that came with the kit were absolutely necessary to clear the engine. Unfortunately my original cranks were 1 piece cranks so I had to buy a bottom bracket($) to use the new cranks. Naturally those really nice pedals didn't fit the new wide cranks so I bought some cheapos($).

    Quiet was my goal. I want to ride on bike paths and the beach with out ****ing people off or being ticketed. I placed rubber pieces between the cooling fins, thanks for the tip motored bikes.com. I also fashioned vibration dampeners out of automobile exhaust hangers to go between the engine and mounting bracket. I never tried it with out the dampeners so I can not say if it makes a difference, I can say that they are holding up. I used rubber between the frame and engine mounting bracket as well but the mount slipped on the frame, my chain went slack and I ended broken down and walking. When I got home I welded the engine mount directly to the frame. This had the added affect of doing away with all that unsightly mounting hardware.
    I fabricated an air cleaner box out of dense closed cell foam which fits over the original air cleaner to quiet down the intake (again never tried it without it).
    For the exhaust, I took the stock exhaust and did some drilling on its innards for better flow. Next I bought a used muffler for an 80cc dirt bike (bought on Ebay $) and welded it right on in tandem with the stock muffler. It's a high performance glass pack with a much larger diameter pipe so there should be no extra resistance to flow but will absorb some sound. The opening is also aimed so sound waves are directed to hit the rubber tire (a little more absorption) then be deflected at the ground (further sound absorption). Finally, I tripple wrapped the whole works with fiberglass tape ($) to absorb sound and some heat protection for my leg. The exhaust has a really nice low tone. Although I didn't try it before my mods I have no doubt this made a difference.

    She started up quickly. A beautiful low tone, real quiet. Then I took off down the street... what a friggin racket! The gear box was so loud once the bike got moving that all my stealth technology was basically worthless. I had filled it with the recommended weight/quantity of lube but it was loud and there was also major resistance to movement, I could barely pedal it with out the engine running (the wide cranks and ape hangers don't help).
    After a while, A LOT of the oil blew out of the little outlet hole and the gears moved much more freely. I can now ride it as a bike but the gear box still provides substantial resistance, the drag when I let off the gas is greater than I can produce from the worthless front brake. Over time the gears broke in and the noise has also decreased, still loud though. I would love to figure out a way to convert to a belt drive or something to get rid of this loud gear box.
    The 4 stroke produces its power at a low RPM and can't produce the high RPM that the 2 strokes can. So the 48 tooth sprocket that it came with is too large. I take off from a stop no problem and do some serious hill climbing but top speed seems slow (sorry I haven't clocked it). I plan on getting a 36t.
    The sissy bar to lean back against and the ape hanger bars make this an extremely comfortable bike to motor on. You recumbent guys would dig it. This thing really gets attention, strangers just come out of the blue asking questions. I tried to cover everything with this lengthy write up, but if you have questions fire away.
    Keep On Ridin On.

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    Last edited by a moderator: Dec 15, 2015

  2. fetor56

    fetor56 Guest

    Well done man,good work......shame about that Hoot GB but u might be interested to know Grubee is supposed to be introducing this belt drive GB soon.
  3. Mountainman

    Mountainman Active Member

    that's a very cool looking motor bike that you got going on there

    easy to understand why many who see it -- wish to know more

    have fun as you ride that THING
  4. srdavo

    srdavo Active Member

    great looking bike.

    good post!

  5. dougsr.874

    dougsr.874 Active Member

    I have just replaced my Hoot gearbox with a Skyhawk 111. Much better unit, freewheels, etc...quieter also.
  6. wheelbender6

    wheelbender6 Well-Known Member

    You didn't take the easy way out in any phase of the build. That's a very unique thumper!
  7. Fetor 56: Sweet ride. You adressed the front brake issue with a nice clean drum. Looks like a custom muffler for some added sound suppression and style. Free wheel rear sprocket for pedaling, thats actually the reason I wanted a pull start motor, once I did the research I realized the freewheel set ups were quite pricey though. And the prototype belt drive, I want one today, you must have connections. We definitely have some similar thoughts on what makes a great motor bike.
    DougSr874, When you say the Skyhawk111 freewheels do you mean that the drive sprocket connected to the gear box has a freewheel? That would be a big improvement, though not as big as a freewheel on the back wheel which eliminates having to push that fat chain.
    Thanks for the comments SrDavo and Wheelbender
    Working on a bike that was flat black has been a pleasure. I could just sand and weld at will. Bash it around with out worrying about the paint, just spray where ever it needed it. Now that the bugs are worked out I'm thinking about pulling it all apart and giving it a nice paint job. I am quite capable of making a mountain out of a mole hill if you haven't noticed.
  8. fetor56

    fetor56 Guest

    Not my ride man....only a Grubee prototype to give u an idea what's hopefually coming- out soon.
    BTW...Stage 2 & 3 GB does have a freewheel on the output sprocket.
  9. MachoMouse

    MachoMouse New Member

    Awesome build man...it looks totally "Mad Max"!!!
  10. bikebum1975

    bikebum1975 Member

    Dude thats a very cool loking bike love the banana seat and sissybar on it I am going to build something similar to that in the spring except I am putting a 2 stroke and a sick bike part shifter on mine when I get the money saved up But nice looking build
  11. Hey cool. Looks Super Comfortable to ride.
  12. Old Bob

    Old Bob Member

    Paint? real hot rods don't need paint.:devilish:

    I like "rat rod" (rat bike) thing going on with the flat black, it makes it look mean.