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Thread: Case Clearance on +4mm Stroker Crank?

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    Case Clearance on +4mm Stroker Crank?

    Hi,

    Does anyone know how much rod to case clearance is considered "safe" for the swing of the rod as it enters the cases? I got one of the +4mm Hotrods stroker cranks that wasn't fully machined around the big end. There is one high spot at the base of the beam that protrudes outwards and makes me a bit nervous. Right now with the rod centered in the bore in the 10 o'clock crank position (from flywheel side), I have around .040", as the rod tips forward 30 degrees, it can touch the cases, only in one area. The last thing I want is the engine to clearance itself while running.

    This was before I did my second pass of clearancing - I ground the cases back to beyond where the sharpie marker is.



    The rear of the case has plenty of room for some reason.



    Front of the cases with rod tipped to center of bore.



    Engine Mock up photo

    Last edited by CTGT2005; 10-09-2016 at 07:38 PM.

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    what youll want to do if you can is put the crankshaft in each case half separately then put the piston on the rod and put on the cylinder. lay the case half flat and somewhat level. by hand just turn the crankshaft and youll get a true representation of where any high spots are. trying to hold the rod centered with your hand is bad idea because if your not holding it exact then the clearance could be more or less of what it really is. .040" is more than plenty imo. avoid grinding the rod or youll probly get metal particals in the bearing. tape off any case bearings so they don't get aluminum particals
    to much power is almost enough

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    Might want to get those tins welded

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    I did that first by installing the crank separate in both case halves, using the stock piston and cylinder as a guide. But for some reason I am second guessing myself. Once the crank was fully installed, it just looks like less clearance.

    I put masking tape over all bearings when grinding, ran the shop vacuum and then blew out the cases out afterwards.

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    Quote Originally Posted by hickwheeler View Post
    Might want to get those tins welded
    Failure rate on hotrods crank tins?

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    Pro-X broken1's Avatar
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    Quote Originally Posted by CTGT2005 View Post
    Failure rate on hotrods crank tins?
    Don't know what the failure rate is on the hotrods cranks but there are some that have failed & it's good cheap insurance as well as peace of mind when it's turning high rpm.
    overkill is an often underrated achievement

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    getting the tins welded is worth every dollar. when my tin came off my motor had around 40hrs on it . the right side inner case took the worst of it an by the time i was done fixing it i spent close to 500 $ i was 3rd gear on the throttle an the bike came to a sudden stop almost sending me over the bars jammed my thumb an bruised both my thighs on the handle bars.

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    Get it welded n true

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    Sphynx rablack21's Avatar
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    HotRods crank are not known for throwing tins. I'm not saying it's never happened, but it is not common. Generally, engine builders don't weld up the tins unless you are running more than 363cc's.

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    Sphynx rablack21's Avatar
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    OP, as to your original question: it looks like you got your parts from Eddie. It wouldn't hurt to call him and ask him. I want to say mine had at least .060, but I can't swear to it.

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    Guys- appreciate all the input. Good to hear a variety of perspectives. I'll call today just to confirm with Eddie. I guess that would have made sense from the get go.

    The motor is a pretty mild build, im not drag racing this, just looking for good reliable hp that keeps up with my modded 450r.

    Specs:
    ESR 330PV - (bore: 75.5mm, stroke:76mm, disp: 340cc)
    Hotrods +4mm Long Rod
    TRX9 Porting
    ESR Cases +.210 height
    2002 CR Ignition, BDT adapter plate
    TRX5 Center mount exhaust
    40.5mm PWK
    ESR Reed cage

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