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SpookyTooth's "Pull More Power From Your Engine"

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SpookyTooth's "Pull More Power From Your Engine" Empty SpookyTooth's "Pull More Power From Your Engine"

Post by DuctTapedGoat on Wed Jun 22 2011, 19:28

Blueprinting - Pull More Power From Your Engine

Here are a few of our inside tricks to building a perfectly running motorized bicycle using the SkyHawk engine.

Blueprinting is a simple process of port matching. The 2 cycle engine suffers greatly from restrictions in air flow. Perhaps 3/4 hp can be gained by following these quick tips.

Remove the intake manifold from the cylinder and notice how much the intake gasket covers this port. To free this restriction, carefully remove the intake gasket and set it aside. Use a high quality, gasoline resistant gasket sealer such as The Right Stuff, Yamabond, or Ultra Grey Gasket Maker. Apply a small but sufficient amount to the mating surfaces of the intake manifold and the intake port on the cyclinder. Wait a few seconds per the instructions of the gasket maker and then mate the 2 parts. Save the intake manifold gasket, it may come in handy later if you develop an intake leak (i.e. erratic idle, poor power, run only on half choke) and need a back up.

The exhaust port should also be matched to the exhaust mount flange on the muffler (the part w/ 2 bolt holes and a large center hole). To do this, you will need a reamer, file, or rasp to enlarge the ID of the exhaust mount flange of the steel muffler. Put your finger into the exhaust flange and feel the lip or overhang of the excess material and compare it to the roundness of the tubing to which it is attached. Simly remove enough material so that the exhaust mount flange ID matches the rest of the tubing. No gasket maker is required after performing this step, only the standard exhaust gasket.

The catalytic converter is a highly desirable piece of equipment on motorized bicycles because the visible exhaust smoke is reduced significantly. Without the catalytic converter, there is a marked difference in the overall amount of oil that ends up on the bike frame, tires, your skin, etc. However, the downside to a catalytic converter muffler is that it increases the amount of back pressure in the engine and thus restricts air flow and power. The catalytic converter mufflers are built to be tamper proof and welded seamlessly. To quickly and efficiently increase power without increasing noise, turn the exhaust muffler upside down, notice that the stock exit tube is offset from the center. Drill a small 1/4" hole in the bottom center of the muffler adjacent to the stock exit tube. By drilling a 1/4" hole in the bottom center of the exhaust muffler you will dramatically increase power without increasing noise, and you will be making the hole barely noticeable to anyone standing above the bike.

Other quick tips that could come in handy. Get a hold of MAP gas or an Oxy-Acetylene torch. All bike frames vary, therefore, you may run into exhaust mounting problems once in a while. Instead of modifying engine mounts or pedals to clear the exhaust muffler, heat the exhaust muffler to a bright glowing red and bend the exhaust pipe while holding it in a vise. Be sure to only bend the pipe while you have the torch on it and it is glowing red. Do not move the heat away while attempting to bend the pipe or else an ugly crease will develop in the metal.

Mounting the throttle handle should be done with care. The 4 parts of a throttle assembly are the 1.) throttle cable, 2.) upper mount bracket w/ index pin, 3.) lower mount bracket with kill switch, and 4.) the inner twist grip that you physically twist with your hand. When installing the throttle, use large amounts of grease inside the upper and lower mount brackets and the inside of the inner twist grip to provide for smooth throttle response. Also when installing the throttle, have the cable mount tab of the inner twist grip pointed upwards while tightening the upper and lower mount brackets. The inner twist grip is sensitive to forward pressure (deceleration) and can lose its forward stop if installed incorrectly or if mishandled by the rider.

Probably the biggest and most helpful tip to ensure good longevity of their motorized bicycle is to be extremely easy on the engine upon initial start up and during break-in. The chrome liner of the cylinder needs cyclical heat tempering to get up to its optimal hardness. In order to accomplish this cyclical heat tempering, the bike should be kept at very low idle and ran for short amounts of time. We recommend a top speed of 15 mph for a 44T sprocket, and trips limited to 10 minutes. Follow this regimen for the first 3 tanks and the engine should develop 1/3rd more power and you will notice that all of the engine noises miraculously disappear.
Blueprinting - Pull More Power From Your Engine

I'm a duct-taped goat.

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