How many hours do you consider a MM engine to be running at full strength?

Discussion in 'Mud Motors' started by Duckman Dan, May 4, 2005.

  1. Mud Doctor

    Mud Doctor Elite Refuge Member

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    The engine decides when it is broken in. If the machining and tollerances are within spec and cross hatching applied correctly on cylinders, piston rods, etc, they break in within a few hours, meaning good mating surfaces, cylinder pressure, oil and compression rings, and valve seating.

    Kawi and Kohler motors don't show any appreciable difference in performance when breaking in. The small Vans do a little, and many of the large vans actually come alive after 10 hours.

    The industry standard is a 4% variation in power with exact motors. All having to do with all the little variable that make an engine run. So, if you have the same engine and same boats/loads, don't be surprised if one runs differently than the other.

    What can you do to help? The four biggest factors in engine performance are lubrication, fuel, throttle and governor settings. There are a long list of component quality issues, but you have no control over that. After running awhile, plugs and valve settings,(kohler excluded, they have hydraulic valve lifters) should be your focus. After the first season, how well you prepared your motor for storage can dictate how your motor runs season after season.
     
  2. Sprigger 04

    Sprigger 04 Senior Refuge Member

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    Drive it like you stole it!!!!!
     
  3. Duckman Dan

    Duckman Dan Elite Refuge Member

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    Mud Doc
    You lost me with "cross hatching" and "good mating surfaces" the later does have another meaning though that I do understand :dv
     
  4. Duckman Dan

    Duckman Dan Elite Refuge Member

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  5. markethunter

    markethunter Elite Refuge Member

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    Think I'd trust what the manufaturer recommends over someone with a website that thinks they know everything.

    I read it. He knows enough to be dangerous..... that's about it. :rolleyes:
     
  6. lax

    lax Elite Refuge Member

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    When I redo a Harley motor I recommend a 500 mile break-in during this time no bogging of the motor and speeds should be kept below 80mph also a lot of on /off the throttle action so as not to egg shape the cylinders which happens when running a steady rpm for a long time. Variations in ring end gap also play into proper break-in. Everyone has a different method, but this hasn't failed for me yet. Overall follow the guidlines set by the motor builder!
     
  7. Mud Doctor

    Mud Doctor Elite Refuge Member

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    Cross hatching is where a hone, or hand abrasive is used in a cylinder to cut little groves that cross, looking like a checker board. This is also done on the inside of the piston rods by hand, to help wear in the mating surfaces (uniform fit with appropriate tollerances based on rate of expansion caused by heat) when the engine is first run. (properly built parts ride on a film of oil not the adjacent part). If you baby your engine during breakin, you will not generate the necessary pressures between surfaces to take advantage of this cross hatching. That is one reason why you should run full throttle after a few minutes and vary the throttle after that for the first few hours. (Amazingly, the engine creates nearly as much force letting off the throttle as accelerating.)
     

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