# Replacing Pushrod in Briggs 445677



## kfreels (Jun 21, 2013)

I have a Poulon mower with a 24hp Briggs intek V twin (445677). 
Yesterday I went to mow the grass and when I started the mower it was running with low HP and making a knocking noise. It seemed like it was running very rich. 
I went through and replaced plugs, filters, changed the oil, changed out the gas, etc and still it ran like crap. 
So I thought I would check the valve clearance per some comments on various forums. I pulled off the first valve cover and all was well. When I pulled the second one however, right away I noticed that something was wrong. One of the pushrods was bent and just laying there on the inside. It was the lower pushrod (exhaust?). 
The upper one appears slightly bent as well.

I've read stories about these pushrods having a tendency to come apart and that you can just buy new pushrods and replace them. I've seen others post that you have to replace the entire cylinder head to do it right. I might go that route but before I do any of this, I'm concerned about what caused it to fail in the first place. I don't want to put a $100 cylinder head on it and then find that there is something wrong internally and that my motor is completely torched and i need a new motor.

Is there any way to verify that the motor itself is fine and that this is all it needs? Is there a way to confirm that what I need is a new cylinder head and not just push rods? I would rather save that money if I can.


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## kfreels (Jun 21, 2013)

OK, I got into it further. The valve spring on the exhaust valve won't compress. It seems "stuck". This is likely what caused the rod to get bent in the first place. Any ideas here?


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## pogobill (Jan 31, 2012)

I found this information from a gentleman called jhwentworth, he seems to be quite up on these things. See if this makes sense to you.

Here is the original question (similar to yours)
I have a sears lawn tractor with the above described engine
Model 445677, type 0476Ei family 6Bsxs 7242vf 276480
It developed a loss of power, found it wasn't firing on one clylinder, removed valve cover. Both push tubes bent and displaced. No indication of valve piston contact nor bent valves. Checked other cylinder and it was OK.


and here is the answer


That's the Intek OHV V-Twin, right?

********* Correction********
If it's the Intek V-Twin OHV the problem is the valve guides, not the seats. I have to remember not to post so early in the morning (before 10:00am). Usually the same source for the problem: overheating caused by lack of air flow over the cylinder. the real fix is to replace the cylinder head and gasket, but people have tried to repair the guides. A new cylinder head should be about $150 including the gasket.





If so, damaged valve seats are a fairly common problem, and usually caused by engine overheating due to air blockage around the cylinders. Sometimes a simple replacement of the valves is enough, but if there's damage to the cylinder it will cost $$$ for a new one. Some people have had luck repairing the valve seats. 

Here's what B&S gas to say about it:
This failure usually occurs due to an overheating issue. Overheating is a cause of engine failure from an engine component material that has distorted beyond a specific yield point. The yield point is the limit of a material at which it can be exposed to heat or mechanical stress and still return to its original size and chemical composition. Overheating occurs from causes such as a lean air-fuel mixture, use of improper fuels, dirt and/or debris buildup on cooling fins, damaged cooling system components, reduction in cooling air, over speeding, or an improper engine enclosure.

Valve seat inserts are installed in the cylinder block using a press fit. A press fit is a method of attaching two mating components where one component is pressed into a machined hole having a slightly smaller diameter than the component inserted. Valve seat inserts are commonly .003 - .005 larger than the machined hole in the cylinder block. The pressed fit retains the valve seat insert in position with a constant force. This force is necessary as small engine have significant responses to heat generated in the combustion process. If the cylinder block expands past the yield point, the force is not present to keep the valve seat in place.

In some cases the valve seat can be peened back into place. However, there is no guarantee this type of repair will add significantly to the engine's life.

Cheers


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## kfreels (Jun 21, 2013)

Thanks for that. I found that thread as well. I replaced the pushrod and it ran fine for a day and when I went back out the next week I had the same problem again only this time the rod appears to have dropped down into the crankcase. So a few questions if you don't mind:
1.) Do I need to pull the engine and tear it down to get that rod out now? Or is it fine sitting in the bottom of the crankcase. I've seen remarks both ways but nothing regarding this specific engine. 
2.) From what I can tell, the exhaust valve is sticking causing the tension to be taken from the rod allowing the rod to drop out. Is there anything I can do to help with a possibly sticking valve without pulling the cylinder head? 
3.) If I pull the head and there is no warping and the guides are where they should be, what is the fix? New valves?? 

Sorry if these a dumb questions. I'm getting a crash course in this because this is really bad timing for me to have to put a lot of money into my mower.


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## stickerpicker (Sep 16, 2003)

If it were mine I'd first try pulling the head and polishing the valve stems as well as the valve guides. They may just be varnished with oil that may have gotten too hot. A dealer once told me about 10 percent of new engines come back for warranty work because of stuck valves so varnish isn't always the issue. 

The push rod has jumped out of the cam follower and with the head off you may be able to retrieve the push rod.


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## kfreels (Jun 21, 2013)

Cool. So I'm going to go pull the head right now. I have a briggs repair manual that says that I should "lightly coat the valve stem with valve stem lubricant". Is this something special or is there likely a substitute that I have laying around that will do the job?


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## kfreels (Jun 21, 2013)

Well, I got the head off and it isn't warped. The exhaust valve has some crud on it. The only thing I can't figure out is if this exhaust valve guide is right or not. It sticks out a lot further than the intake guide but it appears to be in good as I can't get it to budge. Is that supposed to be that way or has it come out?


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