The stock main with no silencerOriginally Posted by loganm
There has been a consistent line of advice from multiple members in your "pistons" thread, but you're too busy being a know-it-all to pick up on it, I'll shorten it up to make it easy:
Start jetting from stock
Do your break-in with a complete, functioning exhaust
You're trying to tune a motor with an incomplete exhaust. How can you dial in your main jet without a complete, properly functioning exhaust?
4 corner scoring?
From smellslikedeath.com:
QuitFOUR-CORNER SEIZURE
This piston has vertical seizure marks at four equally spaced points around the circumference. A four-corner seizure is caused when the piston expands faster than the cylinder and the clearance between the piston and cylinder is reduced. The main causes for this problem are too quick warm-up, too lean carb jetting (main jet), or too hot of a spark plug range.[/B]with it until you've got a complete functioning exhaust fer facks sake.
ETA: From THIS SITE CARB JETTING 101:
Proper Jetting Procedure
After your main jet is dialed in, it's time to move on to the needle.The first step is to get your Main Jet dialed in. This circuit should be done first because it has a trickle down effect.
The Main Jet effects your performance most noticably at WOT. You do not fix a low throttle problem by changing your main jet. When the main is correct, there should be no sputtering or bogging at WOT.
The Needle effects performance from approximately 1/4 throttle to 2/3 throttle. If you're experiencing performance issues in this throttle range but your main jet is correct, this is where you fix it.
Now it's time to adjust the pilot jet and air screw.
This is how I adjust my pilot jet. If anyone has a better technique, chime in.
If the engine does not quickly return to idle after a good rev, it's too lean and needs a bigger pilot jet. If there's bogging when taking off or reving from idle, it's too rich. These problems can often be tuned out with the air screw.
There's a couple techniques for the pilot/air screw. One that I've heard is to set the idle somewhat high, tighten the air screw until the motor starts to die, then loosen it until it starts to die again, then set the screw right in the middle between these two points, then adjust the idle. I haven't tried that technique, personally.
The way I do it is basically by checking off idle throttle response. Adjust it both ways until you get a clean response when you stab the throttle.
When adjusting the air screw, tightening the screw is richer and loosening it is leaner. This is because tightening the screw allows less air to pass (resulting in more fuel in the mixture which = richer), loosening it lets more air through. Edit: depending on the carb, it's possible that this adjustment might be the opposite. Some experimentation will show you which way does what. The type above is the most common with 3 wheelers.
You can lead a fool to knowledge, but you can't make 'em think
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