B&S 18.5 OHV Valve Cap Missing

[BobJohnDeere]

Need some advice.

I have a B&S 18.5 OHV on a Z225 zero turn. Long story short it died - and when I removed the valve cover one of the valve caps was missing. I assume both valves have a cap since the one that was missing had a huge gap. The reason the cap likely fell off was the valve rocker stud had started to come lose and backed out enough that the cap fell off. I could not find the valve cap. I looked behind the rod cover and it still wasn't there. Way in the back there looks like enough room that the cap could have gone into the engine.

Question: Has anybody had the same experience that cap fell off and made its way into the engine ? I would have remembered if it fell out when I removed the valve cover - so if the second cap was there its somewhere in the engine.

Any tips on where to look for the missing cap ? or whether it can stay in the engine (likely at the bottom of the engine in the oil reservoir) ?

Any advice would be appreciated.

The engine is - 31P707-0123-E1
The valve cap is - B&S 691843

 

[bertsmobile1]

Russian roulette is the term that comes to mind
The cap is light enough to bounce around & end up between the crank gear & the cam gear
I will leave it to your imagination as to the consequences of this happening .

 

[ILENGINE]

Or to put it another way. The governor gear is also the oil slinger for the splash lube system in that engine. May have an oil pump and an oil filter but the engine is still primarily splash. lube.

 

[BobJohnDeere]

Thanks for the feedback. Has anybody had a similar experience where the cap fell off and did make its way out of the valve compartment and into the engine ? Just trying to rule out the possibility I didn't notice it falling out when I opened the valve cover.

 

[ILENGINE]

Most of the ones that I have had come loose were in the valve cover or at least in the head when it was located. But if you can't find it laying some place and you are sure it didn't fall out, and it will fit down the hole into the crankcase, then you will need to due some exploratory surgery.

 

[Rivets]

I have come across some engines which only have one cap. After searching and exploring inside finally had to call Briggs and was told my specific model only had one. Sorry I can’t provide exact models, memory doesn’t work as well anymore.

 

[Tinkerer200]

Since it is fairly common for push rods to find their way into the crankcase, it would not be unusual for a valve cap to. I am not aware of there only being one cap though the early engines apparently did not have caps according to the Service Manual. Since you have a very wide gap where you would expect a cap to be, I would say it is in the sump.

IF it were mine, I would try a magnet in thru the oil drain before removing and tearing the engine down. I got some very powerful little magnets which had a hole in the center. You can't drill one. I ran nylon sting thru that and thru 1/8" soft copper tubing which I used for a probe. I never used it but a friend did and had such good luck, he never returned it. You can bend the soft copper tubing different ways to direct your search. I have heard of several people retrieving push rods in this manner though I never tried it myself. IF you happen to know someone who has a "Bore Scope", those work really well for locating parts and inspecting the bottom end of the engine.

Walt Conner

 

[BobJohnDeere]

I'm wondering about the one versus two caps. When looking at the john deere z225 parts diagram - its interesting they list two engine versions. In the first version (21 Engine MM14747, MM14593 ( - 040000) ) they reference a qty of 1 for the valve cap, but in the second engine version the qty is 2 (22 Engine MM16154 (040001 - ) ). Its the same diagram just with a different part list qty. It would be odd that if they did only have one cap - they would have specified in the diagram which valve (intake or exhust) used the cap.

Maybe I'll pay the local john deere dealer a visit and see if they have any insight.

 

[Gord Baker]

I believe we are talking about the Valve SPRING Cap? How is the valve spring kept in without a cap? Usually held in place with 2 tapered wedges (keepers). If the engine still runs OK, put several strong magnets on the bottom of the engine. Epoxy them in place. If there is Ferrous debris in the Crankcase, they may keep it from circulation.

 

[Rivets]

Gord, we are not talking about the valve spring retainer, but the valve cap which goes between the end of the valve stem and rocker arm.