Biturbo Exhaust/Chain Adjuster upgrades

Discussion in 'Motorized Bicycle General Discussion' started by Scootmeister, Jun 2, 2013.

  1. Scootmeister

    Scootmeister Member

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    Here are two easy upgrades I just installed using old parts a fellow motorized bicycle and Moped enthusiast gave me. The first is a Cam-style chain adjuster that simply goes between you drop out and your axle nut. You simply loosen the two axle nuts, twist the cam until your chain tightens to your liking, adjust the opposite side so your wheel is straight, and re-tighten the nuts. Without the adjusters my chain would loosen up no matter how much I tightened the axle nuts due to the engine torque in low gear. Now, there is no way for the axle to slide forward so the chain stays perfectly adjusted eliminating chain slap and excess wear caused by misalignment from the loose chain. The second upgrade is a Biturbo expansion chamber that comes with a 25 or 26 mm ID header pipe which will allow my reed valve engine to breathe a little deeper. The expansion chamber will accomodate several custom silencers. You will note from the photos I have not fabricated the silencer and/or stinger. I hacked and welded the header onto a steel manifold I made from 1 1/2" channel. I like these pipes because the steel is thick and doesn't perforate when I have my Lincoln welder on 105 amps using soft 7016 rods. I installed the pipe in a swept up angle to make the bike look like it's going faster. Attached is a photo of the old exhaust for comparison. Both upgrades took about 4 hours to install. I will report back on how the pipe works (and sounds).
     

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  2. 2door

    2door Moderator
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    An expansion chamber won't do much for a 4 stroke engine. It looks good but don't expect any performance gains.

    Tom
     
  3. Scootmeister

    Scootmeister Member

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    Hi Tom, this is a 53cc Homelite reed valve 2 stroker with a 19mm Walbro, so I'm hoping for a pretty good boost from the pipe over what I had on before.
     
  4. Scootmeister

    Scootmeister Member

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    Here are photos of the final product. I used a B & S muffler and a piece of 57mm pipe to make a low resistence silencer that I pop riveted on the Biturbo. I noticed a significant boost in power, much quicker response and higher RPMs. I'll be tweaking the air/fuel ratio which is easy on this 16mm Walbro carb. All it takes is a twist on the high speed adjustment. A couple of plug chops should do it. BTW, the sound is great, not too loud but deep and rich, without the ringy dingy ping you get from some 2 strokes. One downfall is the extra torque blitzed first gear in my Shimano Nexus hub which has been flawless for 3 years of riding.
     

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  5. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    Gorgeous bike, great custom work and yeah expansion chambers are the way to go with a 2 stroke.
     
  6. Russell

    Russell Active Member

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    First class job! Looks great!
     
  7. Scootmeister

    Scootmeister Member

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  8. bairdco

    bairdco a guy who makes cool bikes

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    i used one of those pipes on magrider's race bike in april. they've got a great sound to them. didn't have the bike long enough to experiment with tuning the header length, but they seem to work well on a 50-80cc engine...

    looks good.:)
     
  9. Scootmeister

    Scootmeister Member

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    Hey Bairdco. Thanks for the feedback. It's been raining so I haven't had a chance to adjust the carb, but sitting in the garage it seems to rev much quicker. And the sound!!!!! I'm hoping that translates into better performance. BTW, you have some great looking builds, I especially like the red fatty!
     
  10. Scootmeister

    Scootmeister Member

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    Here are photos of the heat shield installed. The inside of my thigh is one area I don't want to burn! Sorry for the crummy photos but Tropical Storm Andria is bearing down on us at the moment so I couldn't go outside. The Whizzer hasn't been out much because I've been enjoying this bike too much..rd.
     

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  11. dodge dude94

    dodge dude94 New Member

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    That angle iron? Good job on painting.
     
  12. Scootmeister

    Scootmeister Member

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    Hi Dodge Dude. It's light angle that is pre-drilled and zinc coated. I got a 4 foot section at my local Lowes for about 8 bucks. It cuts with a jig saw. This is the first bike I painted. I used Rustoleum. It'cheap, but is not fuel resistent so you have to be careful to wipe off spilled fuel. Other than that, it holds up reasonably well.
     
  13. mapbike

    mapbike Active Member

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    Best paint Ive found in the rattle cans for bikes and such is spray laquer, I got a fw cans from my local AutoZone store, once it is dry gas doesnt seem to bother it at all in my experience, but yes rustoleum and regular Krylon aint gas frindly at all.

    Just wanted to add this tip for any who it may help since you mentioned the paint and gas issue.
    Peace, Map



     
  14. Scootmeister

    Scootmeister Member

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    Hey Map, thanks for the tip. I've been using Duplicolor on my bikes lately and it works great too. I don't know if it lacquer, but I get it at auto parts stores and it says its fuel and oil resistent on the can. Since I painted the red bike I've been laying down 3 or 4 coats of DupliColor, then 2 coats of DupliColor's clear coat. The paint is more expensive than Rustoleum but it goes farther and the nozzle seems to be much better, plus it seems to be more foregiving with runs. The best part is you can paint a whole bike for 20 bucks.(p)
     
  15. mapbike

    mapbike Active Member

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    You're right about the Duplicolor Paint , I've used it also, just wasn't thinking about it when I made that post about the Lacquer paint , the high heat engine paint is also good because after its cured fuel wont hurt it either.
    Map
     
  16. Scootmeister

    Scootmeister Member

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    Something I learned from this project is the oil from premix will find the smallest escape route and make a mess. So I guess one of the keys to fabricating an exhaust for a 2 stroke is to eliminate all exit points in the system except the obvious one. My first silencer was connected to the Biturbo Expansion Chamber with pop rivets. The B & S muffler that was inserted into the silencer housing was also connected using pop rivets. Unfortunately, pop rivets do not provide a tight seal and oil eventually leaked onto the exhaust. I corrected the problem by using a one-piece silencer and connected it using a hose clamp instead of pop rivets. So far, so good, and it sound much better!
     

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  17. mapbike

    mapbike Active Member

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    That looks real nice.......bf.
    Map
     
  18. silverbear

    silverbear The Boy Who Never Grew Up

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    Good looking bike and the bi turbo sets it off nicely. I have a bi turbo on a Tomos engined Roadmaster bike and like it lot.
    SB
     

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