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Post by dredge3 on May 1, 2010 9:43:00 GMT 1
I am going to have my bore re done. They are .50 over so they will be 3rd over bore .75. All the pistons listed, just list as ypvs.Yet I have 2 sets of pistons and both have 31k on the inside. Which make of pistons do u buy. There is cast etc. Also I have tried measuring my pistons with a digital vernier calipers and the top of the pistons are wider than the bottom.So where do u measure them for tolerance? I take it you take your new pistons to who ever does the re bore
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gadget
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Post by gadget on May 1, 2010 17:53:36 GMT 1
Hi m8, Don't know for sure about the materials available for the pistons, but have heard that the Mitaka pistons are the ones to have (if i'm not corrected first). Not entirely sure at what point the piston is measured on two strokes, but four strokes are measured at the front to the back at the base of the skirt. for clearance/size. whoever does the rebore should have your pistons for reference, tell them what clearance you require and thats about it (rebore will be approx: 90% of the process and the final hone will take the bore out to the clearance you require) It's always good practice to inspect the bores (ports) for sharp /rough edges after rebore has been done (as most engineers do not) and if necessary dress the edges with some really fine wet 'n' dry paper, and then thoroughly clean the bores after with a lint free rag and lots 'n' lots of parafin, you'll be surprised how much crap is left in the cross-hatching.
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Post by dredge3 on May 1, 2010 21:59:07 GMT 1
The pistons fitted are marked up 50. The bore measure 64.45 and prety good nick.I cant measure for out of true, due to the tools I have. The pistons are 64.4. Its hard to get a constant reading, but all looks within range.Pistons have some marks. I dont want to get new pistons and them not to be as good a fit. If new pistons are larger, its no problem
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Post by Norbo on May 2, 2010 9:52:16 GMT 1
The only think you do to di is look at the numbers on top dont worry about anything elce . you just need a set of .75 pistons thats all . just get jap mitacka prox and so on dont get cheepo ones they wont save you any money in the long run after th rings brake.
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gadget
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Post by gadget on May 2, 2010 11:21:53 GMT 1
As you already have the pistons you want to use, just get your machinist to measure both parts (barrels and pistons) with a 'bore parrameter' and he will tell you if the barrels can take the pistons with the required clearance needed after a finishing hone. As you already know, using a digital vernier guage is knowhere near accurate enough for what you are trying to determin, you never get the same reading twice
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Post by carlos on May 2, 2010 13:33:10 GMT 1
I've always given my piston to the person doing the re-bore, then they can bore to the exact size of the piston, as different companies will have different tolerances etc!!!!!
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Post by dredge3 on May 2, 2010 20:26:47 GMT 1
The only think you do to di is look at the numbers on top dont worry about anything elce . you just need a set of .75 pistons thats all . just get jap mitacka prox and so on dont get cheepo ones they wont save you any money in the long run after th rings brake. I dont know which are the cheap ones
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gadget
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Post by gadget on May 2, 2010 23:04:39 GMT 1
Go with MITAKA pistons if you have to buy new.
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Post by bare on May 6, 2010 16:39:17 GMT 1
[quote author=dredge3 board=mods thread=6611 post=70195 time=1272828407 I dont know which are the cheap ones [/quote] Actually ProX are the best of the cheap ones :-) OEM are THE way to go... if the wallet allows... they allegedly have a different taper than the clones. Less noise/wear and far better ring sets.
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Post by dredge3 on May 6, 2010 22:47:10 GMT 1
just remember if you are fitting ypvs pistons into 4l0 barrels to remove the tang at the botom inlet side.... mitaka's are spot on ...good jap piston's.... all i use with no issues.... send pistons and bores at same time and get them to mark left/right on piston to which it was bored/set to piston. check clearance's as per book's...2 thou is about spot on so i have been told and lockside will do to this spec for you. you have a pm btw. gaz Cheers Gary Its all 31k mate
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