 904 ring gap specs?
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Joined: Sep 2007
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OP
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I'm not sure where to look for the suggested piston ring end-gap specs for the Wiseco 904 setup. I have my motor apart and just measured a couple of my my old rings. WAY too wide of a gap in my opinion. Top ring is @.038 in.  , second ring is .025 in.  That's as far as i got. This is after 30,000+ hard miles as a 904 
Howbeit when He, the Spirit of truth, is come; He will guide you in all truth:
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Re: 904 ring gap specs?
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Joined: May 2006
Posts: 525
Adjunct
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Adjunct
Joined: May 2006
Posts: 525 |
This link is to the Weisco installation manuals. On the page you can find instructions for calculating ring/end gaps. Wiseco Product Installation Manuals
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Re: 904 ring gap specs?
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Joined: Sep 2007
Posts: 1,668
Learned Hand
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OP
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Howbeit when He, the Spirit of truth, is come; He will guide you in all truth:
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Re: 904 ring gap specs?
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Joined: Jan 2005
Posts: 3,753
Loquacious
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Loquacious
Joined: Jan 2005
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why did you take it apart and how to the inside of the liners look?
(Former)05 BA tbike pipes, ai removed, Freak, mikuni hsr 42's, 904, ported/polished head, 1mm oversized valves
NOW-2010 silver and black tbird
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Re: 904 ring gap specs?
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Joined: Sep 2007
Posts: 1,668
Learned Hand
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OP
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I took the head off to do some work on it and figured i oughta freshen it up while i'm there. The liners look as good as the day i put it together, but the rings are worn out, both in circumference and thickness. It's really tough getting good shots of shiny metal objects.  
Howbeit when He, the Spirit of truth, is come; He will guide you in all truth:
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Re: 904 ring gap specs?
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Joined: Aug 2009
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Learned Hand
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Learned Hand
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Are you going to re-hone the cylinders for ring break-in? Check with the ring manufacturer.
'04' Black America
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Re: 904 ring gap specs?
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Joined: Jan 2008
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Learned Hand
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Learned Hand
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impressive! I guess that really addresses the question of 'how reliable are the 904s'.
05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter
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Re: 904 ring gap specs?
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Joined: Apr 2007
Posts: 3,063 Likes: 8
Loquacious
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Loquacious
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Doesn't appear to be any taper in the cylinders. Suprised that the rings showed so much wear. Do you remember what the ring end gap was on installation? Is your intake system stock? Is there any source of dirt getting into the engine....cracked rubber boots behind the carbs like Keith found recently.
12 Rocket Roadster
03 Bonneville America
69 BSA Firebird Scrambler
73 Yamaha TX 750
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Re: 904 ring gap specs?
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Joined: Sep 2007
Posts: 1,668
Learned Hand
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OP
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Quote:
Doesn't appear to be any taper in the cylinders. Suprised that the rings showed so much wear. Do you remember what the ring end gap was on installation? Is your intake system stock? Is there any source of dirt getting into the engine....cracked rubber boots behind the carbs like Keith found recently.
No, i don't recall what the gap was on installation.
I'm still running a drilled and gutted stock airbox with the Uni filter.
The rubber boots show no signs of cracking like Keiths do.
Howbeit when He, the Spirit of truth, is come; He will guide you in all truth:
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Re: 904 ring gap specs?
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Joined: Sep 2007
Posts: 1,668
Learned Hand
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OP
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It appears that the desired top ring gap is @ .014-.016 thousandths. That's a HUGE difference from what mine are worn to! I should pick up a fair amount of compression!
Howbeit when He, the Spirit of truth, is come; He will guide you in all truth:
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Re: 904 ring gap specs?
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Joined: Aug 2009
Posts: 1,494 Likes: 6
Learned Hand
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Learned Hand
Joined: Aug 2009
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Usually the top ring has a different gap than the 2nd ring, for expansion. You don't want the rings to bind, for sure!!! I use to have a chart that went by the circumference bore and had different numbers to plug in their formula for the two rings. Maybe you can Google Speedpro or Venolia. EDIT> http://www.aa1car.com/library/ring_info_speedpro.pdf
Last edited by Two_Wheel_n; 03/18/2010 5:28 AM.
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