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20 HP B&S, Motor Tight After Install New Connecting Rods

Discussion in 'Mechanic and Repair' started by Rain Man av, Mar 27, 2008.

  1. Rain Man av

    Rain Man av LawnSite Member
    Messages: 133

    B&S 460777, Type 2276 E1, Code 9803265A. The engine seized after running low on oil. Open the back plate and took off old rod caps. Rods and caps showed signed of severe wear. Condition of rod on cylinder two at journal made motor almost impossible to turn. Removed cylinders and using caliber determined both journals to be ok, ie. not rejected according to specs. Specs are from a B&S repair manual I bought at Sears for L-Head twins.

    I assume that the reject spec published by B&S for the journal means that if my measurement is larger than their reject, then my journal is OK.

    Purchased new connecting rods 498314 std size and measured rods at journal to be 1.625, when torqued. Old ones measured .003-.004-.006 larger. The wear on the olds rods was limited and did not circumnavigate the inside (bonus points for using big word) of the rod, thus I am able to obtain those measurements.

    Did B&S send out defective rods. The journals barely measure

    Purchased a new in-lb torque. After torquing to B&S spec of 190 in-lbs, the motor is hard to turn. According to B&S manual, rods should have some up/down movement on the journal after torque, mine don't when torqued.

    If I loosen the bolts at the rods, the engine spins freely. The pistons, rings, walls all look very, very good. No scoring, no nada, pistons move up/down freely, so I know they no be da problem.

    I polished journals with emery cloth and wiped clean before connecting rods and caps. even put oil on the caps before tightening.

    There was no visible damage to the journals, i.e, scaring or gouging. The connecting rods on the other hand had severe scarring. I treated the jounals with muriatic acid to rid of any alum transfer.

    Any info/input would be helpful.

    If da motor requires da new crank, send flowers.
  2. Jay19LM

    Jay19LM LawnSite Member
    from Mo
    Messages: 31

    You got the correct part #. Sounds like you still have material left on the rod journal. Were there any visual signs of aluminum still embedded on the journal?
    Is the engine all origional. The blower housing with numbers could have come off another engine, just a thought but probably not.
  3. sawman65

    sawman65 LawnSite Senior Member
    Messages: 754

    you must not have got all the transfer off the crank pull down and try again i have never use acid to remove it allways used the emory cloth. it can take hours sometimes.
  4. mpalmiter

    mpalmiter LawnSite Member
    Messages: 4

    Most of my experience is with 5hp racing motors. Possible the rod cap could be on backwards. I had the cap on backwards by accident one time and the rod would not spin, as soon as I loosened the the rod bolts it would spin freely. Installed the cap the right way and it worked like a champ.
  5. IA_James

    IA_James LawnSite Silver Member
    from Iowa
    Messages: 2,592

    Was there two numbers for the reject spec? There should be a go-no go standard for it somewhere. How much larger was your journal than the reject spec listed? If it was much over .005-.008" I'd be thinking real hard about what was up.
  6. Rain Man av

    Rain Man av LawnSite Member
    Messages: 133

    Sawman65 -
    I tore her apart, purchased some emery cloth - medium - fine - and extra fine. I played shoe-shine boy with the journals Started with medium and ended at extra fine (hey, I can see myself) I started with the journal pointing at me, did the shoe shine boy thing, and then turned the crank about 15 degrees, played shoe shine boy, turned the crank 15 degrees, shoe shine boy, turn, shine, turn, shine until I went through one revolution of the crank. :weightlifter:

    Wiped it down and repeated with fine, and then extra fine. Put fresh oil on connecting rod/journal, bolted together, and voila, I have the requisite rod play at the journal like B&S says in their book that it should. :clapping:

    Thank you so very much, now it is time to get out the mounting bolt that broke off. :cool2:
  7. IA_James

    IA_James LawnSite Silver Member
    from Iowa
    Messages: 2,592

    Rats, I thought this was going to be a happy ending where it started on the first pull until I got to the last line there.:cry:
  8. Rain Man av

    Rain Man av LawnSite Member
    Messages: 133

    Theres was only 1 reject spec, 1.622. When I first measured the journal it came in at 1.627. I figured since my measurement was bigger than the reject spec, then I was good to go. What I failed to do was to take an inside measurement of the connecting rod. If i had done that then I would have realized a problem. The connecting rod came in at 1.625. Journal at 1.627, means that the journal was larger than the connecting rod. Law of physics states two items cannot occupy the same space at the same time.

    Lots-0-sanding with emery cloth at the journals to remove the aluminum transfer. Sanded journals down to 1.622 which is reject spec. and bolted on connecting rods.

    It has been a learning experience. I still have yet to get that broken bolt out and I will have to see if all the work was for naught, or for reward. Nothing ventured, nothing gained.:weightlifter:

    I should probably bolt the motor back on to see if the engine is going to hold up before tackling the bolt. It's a catch 22 situation.
  9. IA_James

    IA_James LawnSite Silver Member
    from Iowa
    Messages: 2,592

    Darn physics anyway. Hope it works out for ya and all your work isn't for nothing.:)
  10. Rain Man av

    Rain Man av LawnSite Member
    Messages: 133

    Uhh, it did work out. If you follow the thread you'll see. Sorry if I confused you, but I was replying to your question regarding reject specs.

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