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Enduro Engine - 2 stroke Cylinder, Piston, Tranny, Bearings, Clutch, Pipes & Silencers, etc. |
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#1
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Piston A, B or C?
G'day,
I have just pulled the head and piston out of the bike and will be doing a big end up rebuild now I have more time. Just wondering whether it states anywhere on the head or piston what size I need ( A,Bor C),as I can't see it anywhere? Thanks in advance, Mark |
#2
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Back of the cylinder, at the bottom an A,B, or C will be stamped in the middle.
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#3
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Beautiful...
Thanks Gasser, I had a quick look but couldn't see anything.I will check again. Cheers Mark |
#4
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You can safely go up a size as well for a first top end, so if your an "A" cyl like most are, shop for a "B" piston.
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#5
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Thanks Glenn,
I am about to measure it tonight as a second check.Does anyone know what the factory clearances are piston to bore or ring to bore? Cheers Mark. |
#6
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Unless you have a very good bore mic and/or a shop that has one is doing it, don't bother. The margin of error with lesser instruments is greater than what you are trying to determine. I have measured this years ago on a '00 XC250 with a good 3 point mic and verified its fine, but don't have the numbers handy. The "micro" size difference between A.B,C.D is only 0.01mm. Clearance spec is pretty much industry standard for a liquid cooled 250 2-stroke, I just don't remember off hand. Its related to the piston type (forged vs cast) for the same size. You will be fine with a "B" in an "A" cylinder, many of us here have done it as standard practice. I've even gone to "C" in an older "A" bore on a friends bike that was in good shape after deglazing.
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#7
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No worries Jeff,
I had a bloke measure it tonight( does it for a living), and he measured 72.01 basically everywhere in there . It is a B cylinder by the way. Piston had about 5 thou difference(tolrance), is that about right? I cannot get a workshop manual from the gasmoto link(only the handbook). Cheers Mark |
#8
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tolerance depends on size per GG workshop manual:
200cc STD: 0.3mm, limit 0.6mm 250cc STD: 0.4mm, limit 0.7mm 300cc STD: 0.5mm, limit 0.8mm But differant pistons require differant clearances based on whether they are forged or cast. My Vetex and Athena pistons both came with a small slip of paper stating what clearances were required for each. Go with whatever your piston calls for. If you can find a supplier that knows what A, B, C etc sizes are then you can just ask them for a B or whatever you need without worrying about it. I should add my '00 was a stock "A" piston and it still sits on my desk at work. It is marked 66.33mm.
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jeff '00 XC250 (mine) LTS front and rear suspension, power valve cover, carb jet kit and rear chain glide, RB Designs head mod, BRP tall triple clamp, backyard foot-peg lowering conversion. '04 EC250 (the kids) (he can do his own mods haha!) |
#9
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I will also add that based on your cyclinder size you have a 300cc.
cylinder diameters: 200: std, 62.50mm limit 62.60 250: std, 66.38mm limit 66.50 300: std, 71.99mm limit 72.10
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jeff '00 XC250 (mine) LTS front and rear suspension, power valve cover, carb jet kit and rear chain glide, RB Designs head mod, BRP tall triple clamp, backyard foot-peg lowering conversion. '04 EC250 (the kids) (he can do his own mods haha!) |
#10
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Thanks Jotsby,
I was talking to Scotty of Scotties dirtbikes today and he said the same. By the way where is the workshop manual found these days? I can find the user manual but not the workshop manual. Cheers Mark |
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