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Helpful ReplyB&S 18 hp IC Twin II valve problem

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BobSc
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2023/08/24 19:40:24 (permalink)
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B&S 18 hp IC Twin II valve problem

Bought a used DR chipper with a B&S 18 hp IC Twin II engine and it needed a bit of work. After replacing the battery, starter, and carburetor it started right up and ran fine for about 5 minutes or so. I took it to the site I needed it and started it up to run some branches through it and it ran great for about 5 minutes and then it started acting up. Got it home and pulled a few things apart to check my suspicions it was a valve problem and bingo- one of my tappets is stuck. I got the valve removed and with a screwdriver and a rubber hammer I can carefully tap it back into place and the cam will push it back out when I turn the motor over, but I can't move it by hand at all. Seems kind of weird. It's so tight it squeaks when it is forced out by the cam... 


Any ideas of what would have caused this and a fix that doesn't entail disassembling the entire engine? Also broke two head bolts removing the head cover and now have to figure out how to get the stubs out of the block. I'm thinking weld a nut on the end of the stub after soaking good with penetrant and give that a try... any other ideas would be welcome... 
 
TIA
Bob
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    SRTsFZ6
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    Re: B&S 18 hp IC Twin II valve problem 2023/08/24 19:59:22 (permalink)
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    Sounds like the valve may be bent slightly..
     
    Do you know if the tappet, inside the block, is going back down on it's own? 
     
    Also slightly possible, valve stem carboned up any? 
     
    I would check that, probably pull the valve and clean it.
     
    Re the broken bolts.   MIG welding a nut to the broke bolt with good penetration is often successful..
     
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    BobSc
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    Re: B&S 18 hp IC Twin II valve problem 2023/08/24 20:06:45 (permalink)
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    I checked the valve and it is moving freely. It is the tappet that won't move smoothly, which seems weird to me. All the other valves and tappets are working fine, but this one is being stubborn... 
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    SRTsFZ6
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    Re: B&S 18 hp IC Twin II valve problem 2023/08/25 08:35:19 (permalink)
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    Sounds like it's worn, maybe a flat spot.
     
    To confirm, move it to the other cylinder and see if the problem follows it..
     
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    BobSc
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    Re: B&S 18 hp IC Twin II valve problem 2023/08/25 10:49:21 (permalink)
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    The more I think about it, the more I think I must have a bent tappet. Looks like I'm going to have to get into the crankcase and replace it. 
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    BobSc
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    Re: B&S 18 hp IC Twin II valve problem 2023/09/02 16:40:44 (permalink)
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    Got everything apart and had a new tappet in hand and finally got the old tappet out. Couldn't get the new tappet in and the old tappet looked fine. So I did a little recon and put a drill bit that was .001" oversize through the tappet bore and turned it one turn and pulled it out and found a good sized burr that was in the tappet bore holding things up. That part went back together okay and got the valves back in with a few adult words and now I am fighting with a couple broken head cover bolts that broke taking it apart. 
     
    One other thing I need some guidance on. When I pulled the pulley/clutch assembly off and pulled the bearing to get to the cam gear, the crank gear slipped off its keyway and was loose. Am I right in that timing the cam to the crank, the hole in the cam gear should line up with the crank gear keyway between cam/crank centers? 
     
    I already put the bearing back on the crank shaft but I'm afraid to close it up until I'm sure I have the timing right. 
     
    Bob
     
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    SRTsFZ6
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    Re: B&S 18 hp IC Twin II valve problem 2023/09/03 07:38:02 (permalink)
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    There should be a recessed DOT on both the crank and cam.
     
    Align those up and you should be good.
     
     
     
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    BobSc
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    Re: B&S 18 hp IC Twin II valve problem 2023/09/03 12:56:14 (permalink) ☄ Helpfulby SRTsFZ6 2023/09/03 16:58:27
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    Thanks. I missed them completely the first time- probably because they were covered in oil and crud . Found the answer on a youtube video and realized where my mistake was. Only took a few minutes to pull the bearing, realign the dots, and put it all back together. 
    It always amazes and frustrates me how I can get completely stopped by these little details and not be able to proceed until I find the answer. Not sure what I would do without the internet- probably drink beer and watch TV all day long... ;)
     
    Bob
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