Shop Products
Houzz Logo Print
rboone7760

Breaking in rebuilt B&S opposed twin

rboone7760
9 years ago

I am having my old 16 hp B&S opposed twin rebuilt, bored 30 over with new pistons. What is the best method to break in this engine? The B&S owners manual says for a new engine to run 3/4 throtle no load for 1 hour. The next hour mow at full throtle and low speed then use as normal after that. Any suggestions would be appreciated.

Comments (7)

  • larso1
    9 years ago

    I guess you should probably do as the manual suggests. However, you will probably/possibly get conflicting opinions from others since I have heard everything from no load at part throttle as per the manual, to full throttle under load so that the rings will properly break in and seat. (The idea is that if you don't do this, the cylinder walls will glaze and the rings will then never seat properly, and you will burn oil. Good luck :)

  • mownie
    9 years ago

    That method is a well proven old school way to do it.
    The main things you DO NOT want to do with any engine is to "lug it". Lugging is operating an engine at low RPM, but with a heavy load on the crankshaft. Lugging is often done because an operator believes they can lower the engine RPM to cause a slow ground speed and they erroneously believe they are "babying" or going easy on the engine by not revving it up.
    The direct opposite is actually true.
    Lugging creates a condition where the pressure on the crankshaft (load) is high, but the lubrication system is not operating at full capacity, and the cooling system is also not operating at full capacity.
    Follow the Briggs outline and you will be OK.
    You will be OK also if you simply operate the engine by driving it around in low gear, without any appreciable load (meaning no cutting and no high gear) , with the RPM at about 3/4 for an hour.
    Basically, you need to get through the first hour at 3/4 throttle, no load............and then mow as usual, but in low gear for an hour.

  • bill_kapaun
    9 years ago

    As mownie said, you'll get conflicting opinions.
    Some stem from the way they did things 60-70 years ago.
    I have a hunch that whatever method you use will work just fine.

  • rboone7760
    Original Author
    9 years ago

    Thanks for your help. When would you suggest that I first change the oil?

  • mownie
    9 years ago

    The very first oil change (after major engine machine work) really ought to be done after about 2-3 hours of run time.
    The main purpose of the initial fill being drained out soon after putting into service is aimed at getting any stray particles of metal from the boring/honing operations flushed out of the crankcase ASAP.
    Thereafter, change the oil every 50 hours of run time or once a year, whichever come first.
    I suggest folks do their annual oil change in Autumn just prior to stowing the tractor (or other OPE) for the winter off season.
    My rational is: Old tired, degraded oil out......new fresh oil in. This way, the oil has its entire additive package intact and no combustion byproducts harboring in the oil to corrode stuff during the months of inactivity. Pour in the fresh oil and run the engine just about 5 minutes and then put it to bed til Spring. Next season, you are ready to go, well......the oil is at least.

  • bill_kapaun
    9 years ago

    IF you don't have an oil filter, 2 hours and probably not a bad idea to do it again in 5 more.
    IF you have an oil filter, shouldn't it work? You still might want to do an early change for your own comfort level, but I'd stretch it out to 5 hours for the initial change.

  • MantonJohn
    9 years ago

    Just mow with it..... It is not the space shuttle.....

Sponsored
Kwon Contracting
Average rating: 5 out of 5 stars26 Reviews
Innovative & Creative General Contractors Servicing Loudoun County, VA