Two smoke boring

Discussion in '2 smokers' started by halmc, Nov 26, 2011.

  1. halmc

    halmc Turkey T*urd

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    I have a Yamaha IT 175 that needs an oversized piston fitted. Everyone in my neck o' the woods wants to hone the cylinder, but I want it bored.

    My question: any folks out there in ADV land have a machine shop that they use to bore small (~67mm) jugs? Although I'm in N. Fla, I don't mind shipping via ups, etc to a machine shop in a distant place.

    PS: I've looked for a two stroke section of ADV, but never found one. If this note belongs somewhere else, please PM me and let me put it there.

    Thanks!
    #1
  2. SpeedFourJoe

    SpeedFourJoe Been here awhile

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    I'd check with Enduronut on http://yamahaenduro.com/. He really knows the old Yamahas. I think he charges $40 for bore, hone, and chamfer.
    #2
  3. mykill

    mykill odd

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    Try Gary at http://www.spec2.com/

    He has been doing 2 strokes forever and knows Yamahas intimately. He also did all the boring for Moto Carrera as well as numerous other shops around So. Cal.
    #3
  4. MSrider

    MSrider Rebel with a sixfiddy

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  5. concours

    concours WFO for 44 years

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    The oversize piston fitment process involves both, first we bore, then we hone to final size and cross hatch pattern.
    #5
  6. Strong Bad

    Strong Bad n00balicious

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    This normally is the correct procedure. However, it does depend upon how much material needs to be removed.
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  7. concours

    concours WFO for 44 years

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    All japanese motorcycle pistons are offered in .5mm, 1.0mm, 1.5mm O.S., and so, the minimum bore is .5mm, (he didn't specify the amount needed to clean) way more than is practical to hone out.
    #7
  8. stainlesscycle

    stainlesscycle Long timer

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    surely there's a shop in your area that could bore it. the real question is why does everyone want to hone it? is it not bad, and you just wanna bore it for peace of mind? i know on my it200 that is now on last bore, i wish a hone was all it needed - it200 cylinders do not grow on trees... make sure the ports are chamfered too.... have had a few cylinders come in that were not chamfered, don't know why....
    #8
  9. Duck_Pilot

    Duck_Pilot Retired Roadracer

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    You are incorrect here, Sir. Some OEM & aftermarket suppliers offer in increments of 0.25mm....especially in racing-specific engines. I know this to be true of the Suzi PE-175 - the Yamaha IT-175's ISDE arch-rival. It's worth a look-see in Yamaha's FREE online lookup to be sure.

    *EDIT* I took a quick look on "Yamaha-Motor.com" and saw that the 1982 model had 4 oversize piston kits available, in +0.25, +0.50, +0.75 & 1.0mm. I had not noticed the OP's model year, but I suspect that the same pattern follows for most years, based on my past professional experience with Yamaha.
    #9
  10. anotherguy

    anotherguy unsympathetic

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    Two stroke cylinders are hard on boring tools. The interrupted cut beats the hell outta carbide. That's why I prefer to hone .010"/.025MM. If it needs more than that boring is OK but I'd rather not. Modern stones can take a lot of material out fast. Sometimes with cast in liners boring is needed to square the bore up. Yamaha is particularly bad with that.
    #10
  11. baloneyskin daddy

    baloneyskin daddy bikaholic

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    If the cyl .isn't worn and clearances are fine don't waste the money on a bore job. Theres very little hp.to be gained by simply boring it out, however it will run hotter with each increase in size causing more rapid wear.
    #11
  12. concours

    concours WFO for 44 years

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    LOL, I knew it. I thought of writing "most" but got lazy. Carry on. Hone away.
    #12
  13. halmc

    halmc Turkey T*urd

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    Thanks for all comments. I was interested in boring as opposed to honing as the conventional wisdom holds that honing alone (not the finish honing to which one inmate refers) replicates out-of-round condition, whereas boring ensures a constant radius and squares the bore with the base. No?
    #13
  14. anotherguy

    anotherguy unsympathetic

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    No. A properly honed bore is as round and true and they get. The guide shoes keep the stones from removing in the low spots. It goes-drill-ream-bore-hone-lap in order of precision. I use a hone/stone set similar to this for big bore two strokes or smaller bore with large ports. The guide shoes follow the high spots and make the stones do the same until they're gone. It does take an experienced touch to get a two stroke right.

    [​IMG]

    Does that explain it well enough?
    #14
  15. showkey

    showkey Long timer

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    One thing no matter how the cylinder is resized:

    If it is not done correctly and the shirt clearance is not exact to the new spec (about .0009 to .0012") check the book) and have near zero taper and zero out of round the OP will continue this thread with:

    NOW the engine has ring rattle or piston slap noise:huh:huh:huh:huh

    Bore ( to get a perfect hole) and hone to the perfect size and cross hatch is the best way to insure success:norton:norton:norton

    There are dozens of other threads stating 2 stroke bored or honed by a guy use to chevy block clearances and now the new piston has .003 or .004" skirt clearance with piston rattle after rebuild.
    #15
  16. anotherguy

    anotherguy unsympathetic

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    Well yes if it's done improperly it won't work. Find out where the dirt bike guys get theirs done. Or just send it off to Scott Clough. Experienced and trusted just give him a call.

    Oops. Somehow I thought you were out west. In Florida I'd contact Chuck Quenzler @
    Team Scream Racing
    1988 Carroll St.
    Clearwater, FL. 33765.
    #16
  17. Shocktower

    Shocktower Long timer

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    There is a company here in the PNW that makes sleaves for all kinds of bikes you might want to contact them nwsleeve they make all kinds :evil
    #17
  18. Euromad

    Euromad Been here awhile

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    US Chrome will bore and replate and get you a piston kit for it-check their website.
    #18
  19. slideways

    slideways permanent ex-pat

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