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.
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
