250r - ATC300R Kit question??

**ric** · 02-07-2006, 01:54 AM

Anyone know what the standard bore is for a ATC300R kit fitted to a ATC250R air cooler, Bore measures up at 77mm at present but I had a feeling they were 76mm standard. ?????

**BLAZERONE22** · 02-07-2006, 02:06 AM

76mm is correct.

**ric** · 02-07-2006, 04:49 AM

Thanks Blazerone

Looks like the bore is worn out at 77mm, anyone know what piston I could use to get it workin, Honda only list up to + 1mm oversize???

**BLAZERONE22** · 02-07-2006, 10:57 AM

Well I'm at 77mm right now and I used a wsm performance piston from a Kawasaki 650 jet ski, I had to have the ring pins relocated for it to work with the exhaust port. that cost me $40.00, I'm not sure if I can go bigger or not, I'll have to look. You might check WSM performance website.

**bartjuuuhh** · 02-07-2006, 05:47 PM

hallo I,am also a user of atc300r and I used een standard piston from a Suzuki RM380 (standard 77mm). The only difference was with the original piston was the hight. but i have changed it to the right dimensions. It was very easy! My original 300CC kit piston van 76mm and i'am sure that is the original dimensions, because on the piston was STD written. The piston costed about $100 and it works perfectly

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250r - ATC300R Kit question??