17.5 bends pushrods

[Delicreep]

Hey All...thanks in advance.

I'm stubborn.

I have a 2013 Troy Built riding mower with a 17.5 B+S engine. I have the standard problem with bending the intake (aluminum) pushrod, which I am certain is relate to overheating (happens less or can be avoided if I cut the 3 acres in sections). I keep a supply of them on hand and think I could probably change them blindfolded now.

I have this ritual when I start the mower now... I remove the spark plug and hand crank the engine a few times before starting it using a socket and a breaker bar, and I have noticed that there is often an odd resistance and a sound on the first crank...almost like the valve spring (I assume intake) refuses to compress and then does (or releases without the rod making contact).

Before I replace the cylinder head* I am hoping that some wise soul can confirm my theory that this will help and suggest any other options/repairs.

Like I said, I am stubborn, and prefer to keep things running rather than replace...I just replaced the inner tubes on my 42 year old snow blower (starts on one pull)

Thanks!


* I had to drill out and re-tap one of the exhaust bolt holes previously, so I am leaning away from a valve replacement.

 

[Scrubcadet10]

Make sure your valve guide hasn't moved in the head, they tend to migrate upwards if they overheat/get too hot, and your spring will only go down so far, but your cam is still trying to complete the full cycle and something has to give. usually the push rod. Also, make sure all the cooling fins on the head are clear of dirt and debris to promote cooling and be sure you're mowing at full throttle (sounds counterintuitive, but more air flow=cooler engine)
if you don't mind, provide the engine model,type and code number so we can look up your specific engine and see what we're working with, these numbers should be stamped into the valve cover.

 

[Delicreep]

Thanks Scrub!

Model 31C707
Type 3346 G6
Code 130124ZD

Your description of the valve guide issue sounds spot on.

 

[Fish]

Are your valves missing their little caps?

 

[Delicreep]

Thanks Fish...caps in place, and I am not sure of the phrase, but the gap between the cap and the rocker arm gets checked prior to that manual rotation I mentioned.
(oil check done as well)

 

[Scrubcadet10]

Thanks Fish...caps in place, and I am not sure of the phrase, but the gap between the cap and the rocker arm gets checked prior to that manual rotation I mentioned.
(oil check done as well)

Valve clearance/valve lash.
What is the measurement you get?

 

[Delicreep]

I check both intake and exhaust.. .006 (intake) and .010 (exhaust)
The steel rod has never been re-adjusted.

 

[Scrubcadet10]

Valves are a touch on the loose side, but I don't believe it to be your issue.
Exhaust .005 to .007
Intake .003 to.005

 

[Scrubcadet10]

 

[Tiger Small Engine]

View attachment 67524

Have you ever removed the engine shroud and checked the cooling fins and engine for grass, dirt, debris build up? Set valves at .004” and .006”, intake and exhaust. This is just a run of the mill single cylinder Briggs. Don’t baby it. Make sure oil is changed at needed intervals, check level periodically, and run it.
Visually check the valve guides to make sure they have not moved. If it keeps bending the aluminum push rod, obviously something is not right.