Re: bent pushrod on inlet valve,husqvarna rideon mower
It is one of two problems - your engine uses a cam with a plastic gear - this gear has a tendency to move - it will probably need replacement . there is also a chance that the valve seat is coming loose (overhead valve ) which keeps the valve open - check the distance of the valve stems to make sure they are both out the same distance if they are not then when you put a new pushrod in and adjust it the valve will be pushed too far and hit the piston in turn bending the pushrod
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One ting that cause a push rod to bend is a valve guide that work it way out causing bottoming the spring travel. I haven't seen this person but work with others on finding the problem.
It is strange that both bent would be bent; although a valve that broken free could this too. Since OHV valve guides are generally not available as a replacement part the only solution is to replace the head.
the high lift cam has no compensation and so the valve retainer bottomed out causing the rocker to slip sideways and bend the push rod
you would have been better fitting a prolonged duration cam rather that a high lift for the following reasons
1 --- you can used standard rocker gear
2 ---there is no valve bounce at high rpm
3 --- smoother air flow in the inlet manifold so there is not such a stop/ start action when rpm is low
4--- less wear on cam followers and cam lobes
cam shafts are all about open duration so longer open with smaller lift is better than the same duration with a fast up and down action
On any pushrod engine you have to make sure that the timing is correct or nearly correct when first firing it up, if you had the cam in the wrong position the pushrod had no place to go when the cam lobe came around=bend push rod.
I think one of the intake valves, or a valve pushrod, is bent or warped. When the engine heats up, the metal expands and the valve starts sticking open. That would cause compression to be lost in one cylinder, reducing available power so things drag when you engage the blades. This would also causes air/fuel to be blown back through the intake. I think you'll need to take it to a small engine mechanic. Good luck! Please rate my solution if helpful, thanks.
I find my 2148 runs much happier on the medium grade shell than on the cheaper gas. I did have a nasty POW, which resulted in bent pushrods, or perhaps the bent pushrods caused the POW. After replacing the pushrods, and adjusting same, the backfiring stopped altogether. knock on wood. The 21 is a B&S engine which has a propensity to the bent pushrods. Fortunately for me, my neighbor is a wiz at those fine adjustments.
Check the compression on that cylinder and the adjacent cylinder. If it is not too difficult, it would be good to check all of the cylinders. If there is leakage on the adjacent cylinder there's your problem. The engine is getting pressure on number 8 when the lifter is in the wrong position at the bottom of travel and the pushrod can't help but to bend. If you have a warranty, have the valve springs on 8 checked for proper strength I.E (190 pounds). There should be specifications for this motor.