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XR250R piston/cylinder question

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Hey I bought a project bike for $500 to keep me busy over the winter. I had the bore and piston checked by a machinist who told me they are relatively worn. so when I research my options I find out the 84-85 cylinder/piston (75mm) are different from 86-04 XR250 (73mm) but the latter can be bored to 77mm which is 4mm over and offered by JE Piston and my options are only from wiseco with a 1mm overbore only gaining a 251cc cylinder over the newer bikes 277cc what gives? are the cylinders swappable so I can take advantage of more gains?

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Hey I bought a project bike for $500 to keep me busy over the winter. I had the bore and piston checked by a machinist who told me they are relatively worn. so when I research my options I find out the 84-85 cylinder/piston (75mm) are different from 86-04 XR250 (73mm) but the latter can be bored to 77mm which is 4mm over and offered by JE Piston and my options are only from wiseco with a 1mm overbore only gaining a 251cc cylinder over the newer bikes 277cc what gives? are the cylinders swappable so I can take advantage of more gains?

so your working on a 84/85?

if you change the barrel you have to change the rod from a later model aswell, because its longer.

just go the 1mm wiseco in the original barrel

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All the cylinders can be swapped after trimming the early cyl fins on the cam tower slightly. All the cylinders regardless of year can be bored to 77mm too. Rods and cranks give the same compression height for 84-85 or 86 up. The later has a shorter rod to compensate for the longer stroke. That makes ALL aftermarket pistons compatible too. 77mm on an 84/85 crank gives 262cc IIRC. JE and WIseco both make 77 and 78mm. Arias and Venolia pistons can be found occasionally as well. I've got a 76mm Arias and a 76.5mm Venolia. I've also seen the Arias in 78mm.

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I have a few Venolia pistons for the 84-86 XR250R if anyone is looking for one. I used one in my 1990 XR250R with no problems. They were made for megacycles and the claimed compression ratio is 12:1. The bore required to use this is 76mm.

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