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Discussion Starter #1
I inherited two new pistons with a cb350 I purchased. They are in white boxes with "CB350" and "030" printed on the front of the boxes. The number "581123" is penned on the top of each box. The pistons both have ".030" stamped on the top of the piston. The actual measurement of the pistons is 2.525" or 64.1 mm. Presumably, these are first overbore (0.030"). Three questions. Do the measurements correspond with the assumption that these are first overbore pistons? What would be the required finished dimension of the cylinder bore to fit these? Not knowing the maker, are these from a reliable manufacturer? I have no additional clues to offer since nothing else is on or in the box.
 

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.040" is one millimeter more or less. so you have 64.85mm pistons

'72 cb750
'75 cb750
'76cb750
'82 cx500 (but mine is cool, i swear. Why don't you believe me?)
 

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Discussion Starter #3
I double-checked the measurement. My original number was correct. 2.525 inches is 64.14 mm. Maybe that figure (64.85mm) is the recommended bore dimension on the first over?
 

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pistons are not round. they are oval. 030 is .75mm. 040 is 1mm over. if it has "art" stamped on the skirt, its an original honda part. if it says 030, it is third over. depending on what your planning on doing with the bike, that will depend on your bore clearances. i think, .0010-.0015 is the area youre looking for for piston clearance. give them to the shop when you bore them, and tell them its a street bike, or a race bike and they should be able to do what will work. but you can shoot for .0012. this is all of course applying to a cast piston. if its forged, well, youll have to wait for someone else to chime in. im not 100% up on those dims.

jc

i dont know shit
 

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Discussion Starter #6
Thanks for all the input, guys. I went back and peeked under the skirt and did not find anything interesting. Must be getting old. I remeasured at a point lower on the piston (below the pin) and found that both pistons measure 64.45mm perpendicular to the pin and 64.35mm in line with the pin, thus verifying the oval shape and negating my original measurement, which was taken at the top of the piston. These pistons are cast but no other markings (like "art") are evident.

I'm going to need two ring compressors, a valve spring compressor and a oil filter tool, at the least. Anything else you can think of in the way of specialized tools? Sources?
 

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you dont need a ring compressor, just shove em in. the oil filter tool you ca make from an old socket and a grinder, (13/16") or there abouts. if you want. the valves spring com you can make with a large c clamp and some angle stock.

its how we do it at fathouse racing.

jc

i dont know shit
 

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lowtech for highperformance!
cant afford those cool parts if all yer money goes to tools ya know.

i made a valve spring compressor when i realized mine was gone. it was late, and i just couldnt wait to put the valves back in the motor. so i made one from 2 pieces of angled bar stock welded opposing each other to a large c clamp. i actually copied it from chris. but you can use a large old socket the same. just cut a hole in the side so you can probe out the keepers at the cap. its how i learned to weld! yeah, im an awesome welder. (that was sarcasm)


jc

i dont know shit
 

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Discussion Starter #13
Thanks, Mc69. It's on the way. That's a nice cafe 350 in your bio. Tell me about those rearsets. Does the seat hinge like the original?
 

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That seat configuration did use the stock hinge that folded back but it didn't work all that good. I cut and welded up some new stuff this winter with a aluminum seat pan. Dunno yet what I'm gonna do to attach the seat. But the battery will be under the tail of the seat and all the wiring will be hidden.

Those are stock R6 rear sets and I used all thread as a linkage...works great and keeps the stock shift pattern.
 
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