If its black or/and overly oily then its too rich, if its pale and whiteish then its too lean, you're looking for a medium brownish colour (creamy coffee colour) but if its a tad rich (slightly darker brown) then thats ok too because running too lean will risk seizing your engine. This means to run the scooter at WOT for a few blocks and then cut the engine dead, remove the spark plug and have a look at its condition. Tackle the Main Jet first - do some Plug Chops. From 3/4 to Wide Open Throttle (WOT) the main jet size is the one to look at. From 1/4 throttle to about 3/4 throttle the needle position comes into play. From idle to about 1/4 throttle you are mainly looking at adjustments to the idle mixture screw To do this well you have to understand what parts of the carb do what but the general gist of it is that 3 adjustments cover 3 parts of the rev range. I don't think the boating community would look kindly on a motor that had that short a fuse.On a stock 2-stroke carb there are three main ways to adjust the carb settings/mixture. Back then we saw chambers that gave whopping big increases in HP but, cut the life of the motor to hours. I doubt they are getting the big increases we used to see in bike motors. After looking at the diagrams the chamber has the appearence of an old fashioned expansion chamber and they may have figured a way to make a single chamber work for multiple cylinders. The resinance in each chamber is what does the work and if the exhausts are all ganged together the pulses will cancel each other out.On a four-stroke motor tuning invovlves just the lengths of the intake and exhaust pipes and the resultant improvement is a much smaller percentage.I take some of the above back. When the intake ports open and close and when the exhaust port does the same. The dimensions of the chamber are derived from the port timing. Each expasion chamber is a tuned pipe just like an organ pipe. Texasmark,If you are talking about two-stroke motors the number of cylinders is inconsequential. Tuning results in a more efficient motor that can make a good deal more power by taking advantage of more complete scavenging of exhaust out and fresh fuel in.- Scott A google search for 2-stroke tuning ought to turn up a lot of technical stuff if you want to look further. My description assumes you know something of 2-stroke theory and how it works in regards to porting, timing, etc. Some racing tuners, or stingers, are adjustible in length to handle different engine RPMs. Most tuners are fixed and are most efficient at a narrow range of engine RPMs. As with all waves, the pressure waves vary in length and heighth, so the length and bredth of the tube and placement of baffles are what affect the timing of the tuning.
This is usually accomplished with a tube or baffle, or a combination of the two. The tuning itself involves pressure waves (essentially sound waves) and timing them so that an outbound wave sucks out exhaust and the echo wave effectively shuts the door at the exact time that the exhaust is out, but the next fuel charge has not yet left the combustion chamber. Most older outboards are quite inefficient in this regard, as a traditional 2-stroke design requires some unburnt fuel to exit with the exhaust to effectively empty the combustion chamber of exhaust gasses. Exhaust tuning is a method of scavenging as much exhaust as possible out of the cylinder, while leaving as much of the next cycle's fuel charge in the cylinder.
2 stroke tuning forum how to#
Hi Ron, Hmmm, how to explain this simply.
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