//ArrowChat Code
Results 1 to 10 of 10

Thread: piston to cylinder clearance

  1. #1
    Join Date
    Dec 2016
    Location
    NC
    --
    42

    piston to cylinder clearance

    What do you guys think? My local machine shop made my Wiseco piston .015 inches smaller than my cylinder.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	20170317_181935.jpg 
Views:	138 
Size:	803.4 KB 
ID:	240828  

  2. #2
    Join Date
    Nov 2012
    Location
    Waldoboro, maine
    --
    791
    What trike? What does weisco say? What does your manual say?
    82 250r
    83 Big Red
    85 Auto-x
    If you've done business with me please leave me feedback
    http://www.3wheelerworld.com/showthr...ght=Bren_downe

  3. #3
    Join Date
    May 2006
    Location
    The Open Road
    --
    4,729
    If those figures are indeed accurate, it looks like you are running a 69.5mm piston. Of all the topend I've ever seen, the maximum piston-to-cylinder-wall clearance is usually no more than .0035 in inches. That means that if your piston is indeed .015 inches smaller than your bore, you got WAY too much clearance.

    We could use some more details, of course, but it's not looking good. Are you saying he turned down the piston? Or overbored the jug that much?
    "My local machine shop made my Wiseco piston .015 inches smaller than my cylinder."


    Inches x 25.4 = millimeters

    Millimeters/25.4 = inches




    Sent from my Z958 using Tapatalk

  4. #4
    Join Date
    Jun 2013
    Location
    Oceanside, CA.
    --
    610
    Lets look at it in the positive as I did, the machinist measured the original cylinder bore to be 2.720", new piston measures 2.735", then he could rough bore out .015" with a finish bore or honing to 2.737" giving you a .002" clearance. Still might be tight if as Ironchop mentions if it needs .0035" clearance. Does it run an rattle?

    "HJ" Name:  oldfogey.jpg
Views: 1148
Size:  1.2 KB
    ’84 YT60
    ’85 350x (423cc) with ’81 XL500 head conversion
    ’83 XR500 (628cc) converted 3 Wheel hybrid
    ’73 CB750 K3 converted 3 Wheel hybrid
    ’86 TRX250R chassis XR650L engine hybrid
    ’89 TRX250R (stock )
    ’90 LT500 Quadzilla
    ’85 FL350 Odysses ( water cooled head )
    Lost (sold) but not forgotten ’80 ATC 110 (205cc on alcohol ) ’83 200x ( 222cc ) ’83 200x ( 185s eng ) ’85 350x ( stock )
    added to the collection recently, (2) '70 US90 Aquarius Blue and '74 ATC90 Daytona Orange

  5. #5
    Join Date
    Feb 2010
    Location
    Blossvale NY
    --
    4,567
    Quote Originally Posted by ironchop View Post
    If those figures are indeed accurate, it looks like you are running a 69.5mm piston. Of all the topend I've ever seen, the maximum piston-to-cylinder-wall clearance is usually no more than .0035 in inches. That means that if your piston is indeed .015 inches smaller than your bore, you got WAY too much clearance.

    We could use some more details, of course, but it's not looking good. Are you saying he turned down the piston? Or overbored the jug that much?
    "My local machine shop made my Wiseco piston .015 inches smaller than my cylinder."


    Inches x 25.4 = millimeters

    Millimeters/25.4 = inches




    Sent from my Z958 using Tapatalk
    Agree with Ironchop.... If those figures are not a typo, you have way too much clearance... Usually overbore pistons go in increments on .010"... Think about that for a second.

    Piston/cylinder clearance is usually measured to the ten thousandths

    And always go by the piston manufacturers spec for piston/cyl clearance and ring gap
    Trikes:
    '85 ATC 350R
    '85 ATC 250R
    '86 ATC 350X
    '85 ATC 350X
    '84 ATC 200ES Big Red
    '84 ATC 125M
    '85 ATC 110
    '85 ATC 70/110

    If you have bought from me or sold to me, please leave me feedback here>>> http://www.3wheelerworld.com/showthr...+RIDE-RED+250r

  6. #6
    Join Date
    May 2006
    Location
    The Open Road
    --
    4,729
    Quote Originally Posted by HairyJR View Post
    Lets look at it in the positive as I did, the machinist measured the original cylinder bore to be 2.720", new piston measures 2.735", then he could rough bore out .015" with a finish bore or honing to 2.737" giving you a .002" clearance. Still might be tight if as Ironchop mentions if it needs .0035" clearance. Does it run an rattle?

    "HJ" Name:  oldfogey.jpg
Views: 1148
Size:  1.2 KB
    I couldn't make sense of what was what written on that piece of box top. Hard to tell which figure represents what. Your interpretation makes more sense than mine.

    Sent from my Z958 using Tapatalk

  7. #7
    Join Date
    Dec 2016
    Location
    NC
    --
    42
    What Im thinking from looking at his numbers is

    Bore was at 2.720" and target was 2.737" so he bored .015" to 2.735" and honed the last .002" to 2.737". I would assume the piston measures 2.735" (1/2" from bottom of piston skirt) and it gives you the correct .002"-.0025" piston to wall clearance. This would be the only logical way this would make sense. This would be a .020" overbore cut. figuring in the extra missing .003" is from wear of the previous bore.

  8. #8
    Join Date
    Dec 2013
    Location
    north tonawanda
    --
    20
    im a machinist by trade and yes i agree with perv0. that is the only way it makes sense. 015 thousands clearance is like a hotdog down a hallway and would run like Sh*T and knock like crazy. Rule of thumb .002 to .003 for cast pistons, and .003 to .005 for forged. forged pistons expand larger and need more clearnace

  9. #9
    Join Date
    Aug 2015
    Location
    Portland Oregon
    --
    174
    All of the Wiesco pistons are now forged. The US power sports piston manufactures have come a long way with alloys & designs since they switched from castings to forgings. Modern power sports forged pistons take about the same clearance as cast pistons. Wiesco pistons typically print the recommended skirt clearances on the box. On occasion we question the recommendations on the box & give Wiesco a call to confirm the fit.
    I’m now fitting a typical 100mm; nearly a 4” bore cylinder with a .002” skirt clearance.

    The theory is that plated cylinders dissipate heat faster than cylinders with a sleeved cast iron liner. When we fit a new sleeved cylinder with Wiesco brand pistons, I usually give them an extra .0005” clearance just in case.

    John Tice

    503-593-2908 Alternate 541-595-0310
    www.smallenginemachineworks.com & www.nwsleeve.com
    Turning Custom Cylinder Sleeves Since 1971
    http://forums.everything2stroke.com/...d-the-Shop.com

  10. #10
    Join Date
    Dec 2013
    Location
    north tonawanda
    --
    20
    yes wiseco does. i should go check the one i put in my 250x. i think they called for .0035 clearance. i agree with john, an extra .0005 is good insurance . i just purchased a ebay kit for a yamaha blaster. it came with piston cylinder wrist pin bearing and gaskets and rings. for 64.99 shipped. i was quite suprised when i looked at it. i chamfered the ports a bit more and then ran a ball hone down it before cleaning it up and installing. test fired the motor and broke it in a bit and i was amazed how quiet it was. no rattles. we will see how it holds up. for $60 cant complain if i even get a season out of it

//ArrowChat Integreation Code //