new motor, planning on gasket/port matching, advice?

tire

tire

New Member
i'm getting a 2010 grubee gt5 slant head 66cc motor kit. from my limited to moderate know-how of cars, i was planning on conservatively polishing the intake, carb, ports, and gasket match. i figure a cheap motor such as the one i have will have plenty of seams and burrs, not to mention crappy tolerance between ports/gaskets. is there anything i should be made aware of? i'm not a speed freak (well, not for this little project), but i can't install a motor in my right mind without improving it, it seems. thanks.

i used to p/p intakes on mustangs, play with throttle bodies, carbs, etc. that's all the experience i have.

austin
 
yeah i have some advice,
after port matching it be sure to not destroy the piston rings when you put the cylinder body back over the piston......learned that the hard way.
 
howd you destroy it, i assume you carefully let it slide together and didnt' force anything?
 
tire that sounds like a good idea to me matching ports will definetly improve air flow

i am also going to purchase a 2010 grubee skyhawk in the next few weeks when it arrives i plan on port matching the intake and exaust maybe even creating my own custom intakes by bending copper to the oval shape of the openings

i also want to clean up the tranfer ports i dont know to much about timing so im not sure about making either exaust intake or ports larger just smooth them out with a dremmle

another thing i wopuld also like to try is balencing the crank but with all the research i have done i think it may be better left to a machinist although a 100 plus for a completly trued and balenced crank (well as good as a single cylynder can be )is supposedly a good offer i dont want to spend that much on a 150 dollar engine so if i cant figure a home remedy for crank balencing ill just leave it alone

it would be nice if there was a tutorial about opening up intake and exaust ports (i mean more than smothing them out but making them larger ) from what i understand usually you lower the intake opening and raise the exaust but im not sure how much is accaptable i guess thats where the degree timing comes in somehow but im unsure
 
Here are a few of our inside tricks to building a perfectly running motorized bicycle using the SkyHawk engine. Blueprinting is a simple a 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. Simply 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.
Click to expand...

this is a quote of a email i recieved from justin at pirate cycles forgive me but i am new to this hole forum thing and dont kniow how to put it in a fancy quote box
 
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While most of the above is true & more detail can be found here: http://motorbicycling.com/f52/basics-port-polish-port-matching-16646.html I find the following erroneous for a number of reasons;

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.
Click to expand...

Despite claims to the contrary by a few retailers, a catalytic converter is not "a highly desirable piece of equipment" on a two stroke in particular. It has nothing to do with "visible exhaust smoke" or even "oil that ends up on the bike frame, tires, your skin, etc." The primary purpose of a catalytic converter is to promote the "oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2" with the secondary effect of the "oxidation of unburnt hydrocarbons (unburnt and partially-burnt fuel)" - while this is somewhat effective in a four stroke engine, with a two stroke and it's oil/fuel mix the catalytic converter is overwhelmed in short order and clogs. The high heat needed for this secondary combustion is provided by (excessive) back pressure and while it may function adequately for a short period, the restriction is provided by a "honeycomb" so fine it simply can't deal with the carbon buildup of partially burnt oil.
Catalytic converter - Wikipedia, the free encyclopedia

Additionally there's more than one type of catalytic converter mufflers offered with these kits and the ones that "are built to be tamper proof and welded seamlessly" cannot be bypassed "By drilling a 1/4" hole in the bottom center of the exhaust muffler" as obviously the exhaust gasses are forced through the honeycomb before it reaches the end cap as shown here: http://motorbicycling.com/f13/catalytic-converter-mufflers-15857.html. While it may be possible to modify the one with an end cap fastener such as this one: http://motorbicycling.com/f13/catcon-muffler-mods-17098.html - if indeed you're bypassing the catalytic element itself to reduce back pressure "dramatically increase(ing) power", than what's the point of having the catalytic element in there in the first place, let alone calling it "a highly desirable piece of equipment"?

If you're experiencing an undue amount of smoke/oil drips then it's obvious that you're using an excessively rich oil/fuel ratio and/or your air/fuel mix is also rich. Even with a quality non-synthetic oil mixed at 32:1 you'll have little smoke and almost no dripping, should you choose a good synthetic designed for even leaner mix ratios - you'll have none at all.

There's only one proper exhaust system designed specifically for a two stroke and that's the expansion chamber, if installed correctly and matched to the engine's displacement a proper expansion chamber will also promote cleaner exhaust as it's purpose is to prevent the escape of unspent oil/fuel from escaping the combustion chamber before it can be ignited.


A new catalytic converter on a brand new two stroke will "clean" the perceivable emissions for a very short time by trapping it (oil/fuel/carbon) inside the element and so we're stuck with them as stock as a repercussion of bureaucracy and it's inability to educate itself regarding the very basics of engineering and design. Yet with a little thought and experience it's obvious it's an ineffective "workaround" and actually does far more harm than good.


BTW - the above should not be taken as negativity towards Pirate Cycles as he was just trying to be helpful in passing along info that's been somewhat commonplace, if erroneous. He's an excellent record of customer service and I figure that's what's important ;)
 
favorites, add bookmark... thanks guys! i love things with wheels and motors even if they are both small. :)
 
WildAlaskan said:
well said barley awake

when i first posted the quote up it was not in a box but now it is
Click to expand...


On accounta I'm sneaky and used my powwas for good? :D

I edited your reply and added quote tags: [ quote]wordz go here[ /quote] (no spaces in tags, added to break code). You may have run into difficulty with the quote button as you can't quote a quote w/o manually copying and pasting and adding your own quote tags.

o_O

How many times can I say "quote" and get away w/it? :p
 
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