Impact to Cylinder Head Cover While Running - Backfired to a halt, now won't start

Hello All,
I very stupidly slammed my couple year old Craftsman 917.370950 mower into the fascia/front board of my deck this afternoon. I was using the self-propelled feature which suddenly caught traction while I was simultaneously pushing forward. No one to blame but myself. :ashamed:

Anyway, it seems the cylinder head cover (labeled DHC - it's a Honda engine) took the brunt of it, and is dented in perhaps 1/8 of an inch, maybe more. The mower backfired and died instantly on impact. If I try to start it now it just backfires loudly. Did I destroy my engine? I can't imagine there is a lot of extra room in there for a big dent to not horribly damage things, but is there anything else I should check first before taking the the engine apart?

Thanks in advance.

I would start by removing the valve cover, and see what happened. You will need to remove it and replace it anyway. Worst possibly issue is the cover has hit the camshaft gear, and either broke it or the timing belt.

If nothing is damaged other than the cover, the cover is like around 4 bucks.

Be aware that Honda uses a sealant they call hondabond. It is japanese for super glue. You will destroy the cover getting it off, so don't worry about further damage to the cover.

hondabond Looks like a good high temp sealant. The price also doesn't look too bad for being a high temp sealant.

What is the high temp rating?

reynoldston said:

hondabond Looks like a good high temp sealant. The price also doesn't look too bad for being a high temp sealant.

Click to expand...

It is good stuff, I have used it from time to time. When installed on a clean dry surface, glues parts together rather well.

The shop manual for the Honda GCV160 calls to use either Hondabond HT (high temp) or Loctite 5900 when fitting the valve cover.

1. Clean the engine surface completely.
2. Apply the sealant evenly to a new valve cover, not the engine block.
3. Tighten the four bolts within 10 minutes, and wait at least 20 more before starting the engine to check for any leaks.
The bolts should be tightened to a torque of 9 ft-lbs.

* Hondabond HT part number is 08718-0004, list price $13.47 for a 1.9 oz tube.
* New valve cover for the GCV160 is 12310-Z0J-000, list price $4.52.

FYI, the stock valve cover is made of plain steel, and as you know now, can be dented. This is a rare thing for most homeowners, but commercial guys "run into" :tongue: this problem all the time. Honda's commercial mowers thus have an all-aluminum valve cover, which is more impact resistant. You may want to upgrade to this part, which comes off the Honda commercial GCV190. This aluminum valve cover uses a gasket (so no sealant is necessary!) and four slightly longer bolts (due to the increased thickness of the cover).

* Aluminum valve cover part number 12311-Z2A-000 list price $7.44
* Gasket for aluminum valve cover part number 12312-Z2A-000 list price $1.20
* 6 x 25mm flange bolts (four required) part number 90121-952-000 list price $1.90 each

Based on list prices, it is actually less costly fit the aluminum cover vs. the plain steel (less messy as well, since no sealant is needed) :confused2:

References:

Google any part number to find a Honda Dealer selling it online, or use this link to find a Honda Dealer in your area: Find A Honda Dealer

Honda Power Equipment, Engines and Marine Factory Parts Lookup

Honda Power Equipment Shop Manuals on eBay
Honda Power Equipment Shop Manuals on Amazon

Thanks everyone, the advice is very helpful, especially knowing about the adhesive sealant. I will open it up this weekend and report back with pictures. Going to hold off on ordering parts just yet as I'm sure I'll need something more than just the cover. Also, thanks a bunch Robert for the tip on the aluminum replacement cover. I will definitely go that route, not just for the extra protection which clearly I need :mur: but also to avoid having to deal with using a sealant.

One more thing - I was just looking at the manual and it says my engine is a GCV190-LABHH-ED. Would the above part still be compatible, or is there a larger one up I'd need instead?

NathanF said:

Thanks everyone, the advice is very helpful, especially knowing about the adhesive sealant. I will open it up this weekend and report back with pictures. Going to hold off on ordering parts just yet as I'm sure I'll need something more than just the cover. Also, thanks a bunch Robert for the tip on the aluminum replacement cover. I will definitely go that route, not just for the extra protection which clearly I need :mur: but also to avoid having to deal with using a sealant.

One more thing - I was just looking at the manual and it says my engine is a GCV190-LABHH-ED. Would the above part still be compatible, or is there a larger one up I'd need instead?

Click to expand...

Disregard my question above! I see that you noted the part comes from the commercial version of the GCV190, so I think that answers my question.

I managed to pry off the head cover, see pics below. The timing belt isn't broken or off the gears, and otherwise looks good visually. However, check out the left valve adjustment bolt. (Please forgive my lack of proper terminology.) Would that be enough to account for a non-start condition with backfire on attempt? I'm not sure if it is the adjustment bolt or the actual hinge mechanism that is bent. I sincerely hope it's not the motor mounting points the hinge attaches to.

With my calipers I attempted to measure the distance of the exhaust valve stem to the top of the case compared to the intake valve stem. They seem to match, so I think that I was lucky and avoided bending the valve.

Appreciate any advice on how to proceed further. If a video of the valves in motion would help, let me know and I can make one then upload it to youtube. I'm guessing the next step would be to replace the left hinge/arm assembly, tappet adjuster, and any related bolts/nuts.

Damaged cover. Not pictured, small shiny scratch on inside where exhaust valve adjustment bolt made contact with the indented steel.


Front view:


Bent exhaust adjustment bolt/valve mechanism on side that took brunt of the impact:


Intake side, seemingly just fine:

That was a pretty decient whack you gave it there.
Should not be any problems with the engine as the dent would have been pushing the valves open against the valve spring.
Just have a close look to make sure the retaining collars on the valves have not popped off which is the only problem you are likely to have on the rocker box side.
On the other side there is a possability that the piston have have touched the valve head(s) and bent one of them.
This will be hard to diagnose without pulling the head off. The usual indication is that one or both of the valve clearences will be a lot bigger than it should be.
But as you say the valve lash is still withing specs you may have lucked this one in.
Start the engine without the valve cover on and watch the operation of the valves, if they are nice & regular pop a new cover on , refill the oil and go mow.