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Proper way to measure piston-cylinder w/feeler gau
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[QUOTE="EricGorr, post: 167374, member: 19611"] You guys are scaring the hell out of me:scream: Using a "feelermeter" is about as accurate as using the "eyecrometer". Pistons have unique shapes based on the geometry of the ports. Normally 2-stroke pistons are tapered from top to bottom and egg-shaped with the blunt side on the exhaust skirt. The piston and bore need to be measured independently, thats why every manufacturer lists specs for the cylinder and the piston. Generally speaking, if your plated cylinder is brown in color not gray, its ok, thats using the eyecrometer. The best way to measure the piston to cylinder wall clearance is to start by measuring the maximum piston diameter by adjusting the micrometer for the largest point near the bottom of the piston measured from the center of the intake and exhaust skirts. Then use the micrometer to set the dial bore gage at zero. When you insert the bore gage in the cylinder it will read the difference (actual clearance dimension) and the key areas of the cylinder are at 90 degrees near the top of the cylinder where the rings peak and the bottom of the cylinder where the piston bottoms. Look for taper and out of round dimensions and compare it to the factory service manual. Plated cylinders always wear the most at the top of the cylinder where the rings peak. Sorry to be touchy about this particular subject of metrology (the science of measurement) its just that on a weekly basis I get screamed at by customers who get their brand new plated cylinders returned then have their knucklehead friend stick the piston in the top of the cylinder upsidedown and wiggle it or shove a feeler gage in it and find that it accepts a 10 thousanths shim. They always start off the same way "My buddy says you messed up my cylinder". Then I have to explain this all again, and of course his buddy doesn't own $2,000 worth of gaging or taken a semester of metrology at college so he thinks I'm a back-pedaling idiot trying to baffle him with BS. Feeler gages are for checking spark plug gap and valve clearance, not for cylinder bores. If you're really concerned about the bore clearance, take the cylinder and piston to a performance machine shop and have them measure it with the proper gaging. Good luck:) [/QUOTE]
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Proper way to measure piston-cylinder w/feeler gau
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