piston size

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dillon14dj

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im just wondering does it matter what size the piston is? the old rings are like between 8-9cms so thats like 83mm-85mm?. so what size would i be better off getting i found a 85mm piston and rings on ebay but its like near $200 (and something), but then i found a 83mm piston and rings on there for $145.19 (thats counting the shipping also) http://www.ebay.com/itm/35021431440...AX:IT&_trksid=p3984.m1423.l2649#ht_667wt_1037 would this one work for my 350 warrior??

Or would i be better of just getting this http://www.ebay.com/itm/YAMAHA-WARR...ies&vxp=mtr&hash=item256e7b4930#ht_584wt_1037
 
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Well according to the wiesco part# that you out in the other thread. Unless you jug needs boring out you need an 83mm which is stock bore. JE and Wiesco both make higher compression in that bore.
 
If the cylinder isn't trashed why not hone it & rering? That's be a Helluva lot cheaper than a bore & new piston/rings & not nearly the down time. You can also put it back together w/o the base gasket under the jug for a nice compression bump.
 
Stock bore is 83mm. 83.5mm is .020" over stock (.5mm). 84mm is .040" (1mm) over stock, and so on. No way of knowing what you "need" until you measure your cylinder. If it's within wear limit specs (and in good physical shape), just hone it and keep it the standard bore (or whatever size it currently is). If not, or if you want a larger piston, boring AND honing are needed. My rule of thumb, if there is still good visible crosshatch, no ridging at top of cylinder, and there is no scoring that can be felt with your fingers or fingernails, hone it and call it a day. Obviously visually inspect the cylinder after the hone to make sure any scoring has been removed/cleaned up. But, usually I just bore them out and start fresh.
 
Gen1Pat said:
Stock bore is 83mm. 83.5mm is .020" over stock (.5mm). 84mm is .040" (1mm) over stock, and so on. No way of knowing what you "need" until you measure your cylinder. If it's within wear limit specs (and in good physical shape), just hone it and keep it the standard bore (or whatever size it currently is). If not, or if you want a larger piston, boring AND honing are needed. My rule of thumb, if there is still good visible crosshatch, no ridging at top of cylinder, and there is no scoring that can be felt with your fingers or fingernails, hone it and call it a day. Obviously visually inspect the cylinder after the hone to make sure any scoring has been removed/cleaned up. But, usually I just bore them out and start fresh.
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this may sound dumb but i dont know how to hone it?, i know the cylinder looks fine, feels soft and has like no marks on it.

but what ur saying it would be more easy to just get this http://www.ebay.com/itm/YAMAHA-350-...es&vxp=mtr&hash=item4ab65a76a1#ht_2215wt_1270 put it in, with new gaskets, hope the bike starts after lol. and then just sell it!
 
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To do it yourself, get whats called a flexhone. Put that into a drill with a variable speed trigger, put the cylinder in a benchvise (not too tight mind you), use a good amount of oil on the clyinder walls, and insert the hone. Use a medium-slow throttle speed and move the drill/hone from the top of the clynder to the bottom at a medium speed. The objective of honing is to create crosshatch (basically thousands of little X's on the walls). Go up and down too fast and you'll create more of a spiral. Use too much drill speed and you'll make more cuts around the diameter of the cylinder, and will have never little Xing. Not too hard really.
 
Gen1Pat said:
To do it yourself, get whats called a flexhone. Put that into a drill with a variable speed trigger, put the cylinder in a benchvise (not too tight mind you), use a good amount of oil on the clyinder walls, and insert the hone. Use a medium-slow throttle speed and move the drill/hone from the top of the clynder to the bottom at a medium speed. The objective of honing is to create crosshatch (basically thousands of little X's on the walls). Go up and down too fast and you'll create more of a spiral. Use too much drill speed and you'll make more cuts around the diameter of the cylinder, and will have never little Xing. Not too hard really.
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do you really have to hone it?, i just went ahead and ordered the 1 piston and rings off of ebay for $130. what would happen if i dont hone it
 
dillon14dj said:
do you really have to hone it?, i just went ahead and ordered the 1 piston and rings off of ebay for $130. what would happen if i dont hone it
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Rings won't seat. Burn oil. Low compression, blow by. Oil dilution, Bearing failure to name a few.
 
And if it doesn't smoke it won't be long before it does. Honing removes imperfections in the cylinder wall, and allows the rings to make good contact, and allows the rings and wall to breakin to one another.
 
Gen1Pat said:
And if it doesn't smoke it won't be long before it does. Honing removes imperfections in the cylinder wall, and allows the rings to make good contact, and allows the rings and wall to breakin to one another.
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so to cut to the chase when i get the new piston i should take the cylinder to a shop that works on atvs and have them hone it??, also i was told that when putting the piston in im supposed to make sure the rings are 180 apart? (whatever that means)
 
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