kawasaki999
Member
I agree with astring, over 50cc and it wont be legal.
What HP/size are your motors?
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Vishnu Tensleep
Member
that big of a difference between 4cycle and 2cycle?
This post and another in this thread list major HP with 49 or 50cc two-stroke engines, as compared to the HP for 4-stroke. Are these numbers right, and if so why is the top speed not that much different?
This post and another in this thread list major HP with 49 or 50cc two-stroke engines, as compared to the HP for 4-stroke. Are these numbers right, and if so why is the top speed not that much different?
loquin
Well-Known Member
a 2-stroke generates power on every rotation of the crank, whereas a 4-stroke generates power every other rotation. Theoretically, a 2-stroke can produce 2X the horsepower per cc over a 4-stroke.
And, a tuned pipe can also increase horsepower (but, in a limited RPM range.)
A 4 stroke is cleaner, and it offers more torque than does a 2-stroke, though.
And, a tuned pipe can also increase horsepower (but, in a limited RPM range.)
A 4 stroke is cleaner, and it offers more torque than does a 2-stroke, though.
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ZnsaneRyder
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Great reason to get a 4 stroke. No smoke, and cleaner, more efficient burning, and no oil&fuel mixing!!!
J
JemmaUK
Guest
No, no and again no.
A properly set up tuned pipe can increase horsepower in all engine modes to a lesser or greater extent - its theoretically possible that one could be made to provide the same increase in all areas of the powerband - using technology similar to the adjustable induction rails used in such engines as the 4 litre and 5 litre BMW petrol motors.
True, you have to mix fuel. But it is extremely unlikely that with a modern well maintained engine (even on high relative mileages) that you will get smoke. Smoky 2-strokes were relegated to the 1980s-1990s since which time they have been cleaned up to EPA specifications by various different methods. In the case of my tanaka it seems more prone to just spitting out the excess oil rather than burning it.
It is as likely that, with modern oils, you get smoky 2 or 4 strokes and the reason is simple in both cases - a worn engine. In the case of the 2 stroke there is also the possibility of over oiling the mixture. Its more likely that a over oiled mix will cause plug fouling than clouds of smoke.
On the matter of cleanliness - its not so much a matter of 'worse' pollution as 'different' pollution - specifically in the case of NOx emissions in the 2-stroke. This was what made chrysler eventually pull their plans for a two stroke powered neon saloon (I kid you not) and even then they would have passed most tests excepting the insane california regs. Oh, and the SRT-4 shows what american companies can do if they want to when it comes to 4-cylinder performance... roughly equal to what Vauxhall did in 1989! with the XE powered cavalier GSi2000 & calibra coupe.
Jemma xx
Adding a 'tuned' exhaust is essentially increasing the engine's Volumetric efficiency, on the exhaust side. Every advantage has a disadvantage. Making Efficiency gains in one area without considering other areas may or may not see increased performance realized at desired or key locations on the power curve. Even overall performance can deteriorate. Carb venturi size, intake port design, valve head diameter and stem design, cam profile, ignition timing and gear ratios should be considered. All systems acting in concert with one another provide results. Increasing Thermal Efficiency is a challenge. Only about 20% of the gasoline in your tank is actually used to produce work to convert chemical energy into thermal energy and onto mechanical motion,to end up as power (work) and torque. The hotter the engine operates, the more efficient it is, to a point that is. Mechanical Efficiency can be increased by reducing friction within the engine and drive line. A new engine has poor mechanical efficiency at first due to high friction from the cylinder wall crosshatch honing. You will notice that as the engine 'breaks in', power and torque levels increase and stabilize. Certain oils and lubes reduce friction more than others.
When an engine comes out of the factory, it is engineered for reliability, reasonable power and low emissions. The engineers took the time to 'balance' (match) the parts. Example: designing all the parts to work well together, in efficiency terms. Think of it like this: you decide to remove the stock muffler to install a 'performance' exhaust system. You may or may not realize performance gains. Think of the engine as a pump. If you make the outlet channel bigger, will it make the inlet side automatically flow more too? Think about it. Most carbs can handle the modest increased CFM but the fuel jetting would have to be addressed to enrich the air/fuel ratio accordingly. More air requires more fuel to maintain the proper AF ratio to around 14.7:1.
There are many cool tricks you can do to squeeze more power from an engine. I bumped up the compression ration on a two stroke and bolted it down to a workbench. I ran alcohol and caster oil in it with opened up jets. That puppy SCREAMED! Balancing an engine's rotating assembly like the flywheel, crankshaft, clutch hub assy, etc. really works!! Getting the air that enters a carb to enter straight (as in a stream of air) will also help. On 4 strokes with adjustable valves, tinkering with valve clearances can add a little performance at certain RPM's. Keeping the valve heads clean and carbon deposit free ensures continued performance.
Most of the stuff i played with over the years have been big engine muscle cars. the same can be applied to bikes too! Vibration and un-balance are power working against you! Something out of balance by 1/4 ounce can turn into nearly a hundred pounds of imbalance at high RPMs.
When an engine comes out of the factory, it is engineered for reliability, reasonable power and low emissions. The engineers took the time to 'balance' (match) the parts. Example: designing all the parts to work well together, in efficiency terms. Think of it like this: you decide to remove the stock muffler to install a 'performance' exhaust system. You may or may not realize performance gains. Think of the engine as a pump. If you make the outlet channel bigger, will it make the inlet side automatically flow more too? Think about it. Most carbs can handle the modest increased CFM but the fuel jetting would have to be addressed to enrich the air/fuel ratio accordingly. More air requires more fuel to maintain the proper AF ratio to around 14.7:1.
There are many cool tricks you can do to squeeze more power from an engine. I bumped up the compression ration on a two stroke and bolted it down to a workbench. I ran alcohol and caster oil in it with opened up jets. That puppy SCREAMED! Balancing an engine's rotating assembly like the flywheel, crankshaft, clutch hub assy, etc. really works!! Getting the air that enters a carb to enter straight (as in a stream of air) will also help. On 4 strokes with adjustable valves, tinkering with valve clearances can add a little performance at certain RPM's. Keeping the valve heads clean and carbon deposit free ensures continued performance.
Most of the stuff i played with over the years have been big engine muscle cars. the same can be applied to bikes too! Vibration and un-balance are power working against you! Something out of balance by 1/4 ounce can turn into nearly a hundred pounds of imbalance at high RPMs.
5
5-7HEAVEN
Guest
Twin Mitsubishi 2.2 hp engines on "Mr. Hyde", a Raleigh 7-speed cruiser. Awesome idle, a lowend-midrange rumble like a swarm of bees, excellent traction in wet weather due to all-wheel drive. Front friction drive, rear chain drive. Easy 20 mph cruising speed.
My "Girlie" cruiser with modified pocketbike engine on friction drive.
Of course, they're illegal.
My "Girlie" cruiser with modified pocketbike engine on friction drive.
Of course, they're illegal.
Me497
New Member
Mine has a 5hp tecumseh which we need to keep a low profile on because its supposed to go 49.7mph!!!!!! hopefully we get it finished before winter
Me497
New Member
Well i guess mine is illegal and do i care if it hits 50MPH? nope as long as i'm in a place that is awesome for riding that you wont get caught at...
ZnsaneRyder
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