What is the circular cap on top of the engine (Kubota M4050)

[Baig]

Hi, just wondering if anyone knows what these small circular caps are beside the inspections caps are on my Kubota M4050? I (think) I noticed some oil leaking from one so I tightened it slightly which caused the engine to misfire. I have done my best to undo the damage, but I would like to know what they are called (so I can do some more research), or if there is a way to properly adjust/tune the engine.

Thanks for the help!

 

[hagrid]

Due to the lack of fasteners on its periphery I'd say those are fasteners holding down your rocker cover. How tightening one caused your engine to start misbehaving is troublesome.

 

[Dave_eng]

My guess is going to be in a different direction than hagrid.

Your engine is equipped with an engine decompression system according to the parts manual.

I am thinking these openings, which are in the same place but of a different style than yours are to allow access to individual valves, to bleed off engine compression to aid starting. Likely under the caps are adjustments.

Dave

 

[hagrid]

That would explain the misfiring.

 

[007kubotaguy]

The valve cover gasket is old now. You tightened it down to stop the leak. Now the decompression portion of the valve cover is out of adjustment. I would replace the valve cover gasket and replace the rubber grommets under the nuts you tightened. This will probably take care of your problem. If not you're going to have to remove the other small covers go through the process of adjusting the decompression portion. I would also adjust the valves when you have the valve cover off. Great old tractor.

 

[Baig]

Thanks, guys! I think you are right about the valve cover gasket, as I have recently seen a small amount of oil buildup right beside the valve cover and some of the rubber grommets look quite old.

 

[Baig]

Also, for reference, I pulled one cap off and this is what was underneath. I am not sure what I am looking at, however.

 

[hagrid]

Something has been hitting the top of that decompression plunger.

EDIT: that's not the decomp plunger, it's just a stud. Someone's been hitting it like a red-haded step child.