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Hot!B&S engine, 23 HP, back fire through intake

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RC62
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2020/05/22 09:27:09 (permalink)
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B&S engine, 23 HP, back fire through intake

JD Z425 zero turn mower, mowing and then not.  Back fire through the intake, cylinder to the left facing the breather.  Removed plugs and confirmed cylinder/valves not working.  Removed covers and one push rod is missing, the other is bent.  Presume the missing rod is wound up in the sump but engine turns freely.  Also presume that a loose exhaust rocker bolt allowed the push rod to drop out, this and the back firing, then caused the intake push rod to become bent.  Question, if I separate the sump, find and remove the aluminum rod, look for physical damage to anything, replace the sump - gasket and seals, install new push rods, set all back lash gaps to .004 or .005, lock tight rocker bolts, does anyone see an issue with this plan?  Nothing else appears wrong with the engine.  Some other mentions about valve guides missing or loose but I haven't gotten that far.  Don't see guides as replaceable parts.  Thanks for any assistance.

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    AVB
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    Re: B&S engine, 23 HP, back fire through intake 2020/05/22 10:10:41 (permalink)
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    Provided that valve guides, valve seats, and valves are all still good then there should be no problem doing what you want to do. But to be on the safe side I would pull that head in question for at least an inspection.
     
    And yes the valve guides are non replaceable on most OHV small engines so if one has moved it is a new head time.
    The last Briggs Twin cylinder head I brought cost me $145.
    RC62
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    Re: B&S engine, 23 HP, back fire through intake 2020/05/22 10:27:49 (permalink)
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    Thanks AVB for the quick response, 
    More information, other head, valve clearance is about .010, maybe .009 but intact and operational, presume that due to the nearly 2 times the clearance and then a loose rocker bolt is the reason the push rod fell out, and no other issues that would cause the rod to drop.  Plan to reset all the valve clearances to around .005.  If I remove the head, not sure what to look for other than obvious damage.  Probably can compress the springs and remove the valves but again, no way to lap the valves or do critical inspection other than look for obvious issues.  Jacks has a head for about 165 or so, also which is #1 and which is #2?  I'm viewing the engine from the front, air cleaner side, and see a left side and a right side.
    Roy
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    Re: B&S engine, 23 HP, back fire through intake 2020/05/22 11:31:58 (permalink)
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    If the valve guide has slipped you will notice a band on it right above the cylinder casting. It is not just a matter of driving it back in. I have heard of people pressing the guide out and knurling it on a lathe. Another shade tree repair is cutting a v groove in it at the edge of the band then staking it in with a flat punch but neither is rcommended by the factory.
    You will notice the heads are offset, the closest to the flywheel is #1.
    RC62
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    Re: B&S engine, 23 HP, back fire through intake 2020/05/22 11:59:03 (permalink)
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    Thanks Roy,
    Any way to confirm if the guide has slipped from the outside looking under the valve spring?  It would confirm if the head has to come off and be removed or replaced, if not pulling the head is a $20 gasket and possibility of stripping out a head bolt.  Don't want a repeat of this issue but like to confirm the need to pull the head.  Still have to open up the sump and find the missing push rod, hoping it didn't damage anything internal.
    Thanks,
    AVB
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    Re: B&S engine, 23 HP, back fire through intake 2020/05/22 12:17:18 (permalink)
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    As for which head is which. With heads and intake facing you #1 on the left and #2 on the right.
    VW5767
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    Re: B&S engine, 23 HP, back fire through intake 2020/05/31 08:27:35 (permalink)
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    I have been chasing the same issue on a 24hp. The guide was pushed out so I pushed it back in an peened it in place. I replaced the set of push rods again and went mowing. It was running for an hour or so and the push rods bent again. It was running perfect before that. I pulled the valve cover and the guide was still in place. The valve seems to be seating fine and they move freely. 
     
    So why am I still bending push rods?
     
    Thanks for your help!
    AVB
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    Re: B&S engine, 23 HP, back fire through intake 2020/05/31 08:51:23 (permalink)
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    Probably still an issue with the valve guide and valve. Replace the head.
    VW5767
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    Re: B&S engine, 23 HP, back fire through intake 2020/05/31 14:38:40 (permalink)
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    I have one on order.. $147. I should be mowing again this weekend. 
    RC62
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/01 09:23:55 (permalink)
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    VW5767 let me know if that works for your engine.  I haven't gotten the 23 HP back together, still waiting on parts.  Hoping the loose rocker are was the only issue driving loosing the exhaust push rod and without that the intake rod became damaged.  Once back together if it doesn't resolve the issue, sounds like a head replacement may be on the list.  Where did you find a head for $147?
    VW5767
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/01 10:04:57 (permalink)
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    Of all places Walmart. It comes on Thursday. I will let you know how it went.
    VW5767
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/01 10:07:38 (permalink)
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    The part number I needed was 84001918. Yours may be different.
    RC62
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/01 10:18:32 (permalink)
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    That's just a bit mean, on a small business parts house forum and you get parts from Walmart.  I understand and don't know how Walmart can provide a part that they probably have no idea what it actually is, but they can get it to you cheaper, somehow, and it all probably comes from the same place, overseas!  Thanks,
    Roy
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/01 11:14:05 (permalink)
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    X2!!
    AVB
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/01 12:30:05 (permalink)
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    He actually paid the suggest list price and the part would be coming from an US Briggs distributor. Now Briggs is most likely getting the heads from China however.
     
    That 84001918 (#1) head current costs me $115 from my distributor. Jack's price is above my distributor list price. Many other sites are higher too. Even Power distributors is $133.11 and it is dropped shipped. Now the two distributors that I prices from only sell to resellers (repair shop and retailers).
     
    The only thing Walmart can provide is free shipping. Most likely Walmart will not honor the Briggs warranty either like my distributor will not honor the Briggs warranties. Claiming it is a Briggs warranty policy and the local dealers are to honor the warranty. Guess what the local dealers around refuse to honor the Briggs warranty unless they sold the part or engine directly.
     
    Last year I had to pay $130.50 for the 84001919 (#2) head. And originally it was suppose to be both heads then Briggs superseded the PN to the current PN make the price for one head. Good thing I didn't pre-sold the head as I would got burned for $60+ dollars.
    RC62
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/01 12:54:34 (permalink)
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    Found an online supplier, Small Engine Supplies (SES) for $122.95, probably have to pay shipping.  My assumption is that as long as I purchase on line there probably won't be a warranty unless absolutely bad parts upon arrival.  If I go local then I can face to face work out a warranty, but haven't asked what the local supply house would want for a single head.  One repair shop indicated that a replacement head would be $500 or so, I have to assume that has labor in the price.  Saw a complete replacement engine for $750ish and $60 shipping, so at some dollar point I'd recommend replacing the engine.
    AVB
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/01 13:21:32 (permalink)
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    I know I do if the parts exceed 50% of replacement of the equipment or engine depending what I am working on. That is why I still have 84001919 head as when I pulled the head the cylinder was shot and the engine was needing to OS pistons. That plus the head exceeded the threshold I have set so the customer called it DOS. Besides the mower looked like had been to heck and back. It went to the recycler.
    RC62
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/01 13:43:57 (permalink)
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    My 23 hp Briggs may need a head, but I think it will be the 84001918, head #1, otherwise I'd suggest a resale.  If I could ever get parts to see if just the push rods and the rocker solved the issue.  I'm working this for free, mower belongs to the neighbor.
    VW5767
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/01 16:40:15 (permalink)
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    It was a $30 difference between Jacks and where I got it. Gotta save a buck or two these days. 
    RC62
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    Re: B&S engine, 23 HP, back fire through intake 2020/06/02 08:35:30 (permalink)
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    Finally got some parts, not all but some.  Putting the sump back on and it appeared there was no option regarding the governor placement, lever only turned about 90 degrees, so all the way counter clockwise looked like the right path.  Once in place and the sump attached the rod has movement and my etch marks line up on the governor arm to shaft.  Anyone know if this is correct or if it is possible to do this incorrectly?  Another question I can't seem to find the answer is the coil(s) to flywheel setting.  Seems like I remember about .020" is a good point, 2 playing cards against the flywheel and slide the coil to a snug fit.  From the top of the engine, what is the correct rotation, CW or CCW?
    Thanks, 
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