OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Honda Engines Honda GCV135/160 cylinder head cover gasket mods?

I had to take off the pressed metal cylinder head cover (the one that says 'OHC') on my Honda GCV135 due to it having a big ding that prevented the rockers underneath from opening the valves. Put that on the list for 'rasons why your mower won't start'.

Now it's time to put it together again. But, what are the opinions of liquid gasket sealant? I just spent most of an hour carefully removing the remains of the factory-applied black rubbery sealant from around the head, without having the debris fall into the crankcase (from where, according to Sod's law, one tiny fragment will almost certainly lodge under the valve seat). Despite surgical care, one or two fragments fell in.

Now I'm going to just put more goop on (Loctite blue RTV is what I've got) and bolt down the cover. So that next time I open it, I can spend another hour scraping the rubbery goop off again. I dream of a cork gasket. Has anyone done this? Would it be an improvement, to cut a cork gasket and fit it instead of gasket goop?

The Honda GCV (overhead cam) series of engines, including yours, are marketed as "Residential" engines, where the GXV (pushrod) engines are marketed as "Commercial". The difference is, essentially, how much they cost to build and how long they are expected to last. Hence the GCVs lack such sophisticated attributes as replaceable gaskets, an oil seal on the governor arm shaft where it goes through the side of the crankcase, a detachable cylinder head, and a gear-driven camshaft. This does not make them run badly, it just means they were designed with a lesser degree of attention to making them durable and repairable.

Remember, engines which have gaskets have places to put them. Engines which are intended to be sealed with goop only need places to put thin lines of goop. If you try for a gasket but do not design it correctly, you'll have an engine full of loose bits of gasket, which are pretty sure to be more of a problem than loose bits of dried RTV silicone.

By the way, it would be advisable to take a close look at the plastic cam that operates both valves. If the cam cover was really stopping the valves from opening, it has to have broken the cam belt, or wiped the lobe off the plastic cam, or flexed the pressed steel rocker arms to an alarming extent (those rocker arms have a reputation for breaking in service). It seems more likely the dent was on the other side of the rocker pivot, and it kept the valve from closing, rather than keeping it from opening. If that were the case, no damage is likely to have been done.

I had a good look, and it seems you are correct, Grumpy, as to what action was prevented by the dent to the rocker cover. No damage done. I'm about to lay the RTV on and seal it up.

Just as a follow-up, now that the rocker cover is back on, I flushed the mower twice with left-over (clean) car engine oil, and that washed out the crumbs of old sealant that had fallen into the engine while I was scraping it off. More came out than I realised had fallen in. Hopefully that's got rid of all the bits.

The silicone rubber RTV is a soft material, and it isn't all that likely that small amounts of it will cause a problem Ian. It might be awkward if a large lump got on a tooth of the cam drive, toothed rubber belt, so you certainly don't want any big chunks of silicone rubber in there.

Sounds as if you are probably ready to give it a run.

Hoping to give it a run soon, but I am renovating the mower deck - I found a lot of rust under the layer of grass pulp that I never cleaned off. So I've wire-brushed the underside, given it phosphoric acid, and will give it a coat of epoxy enamel and then bitumen paint. Everything should be tip-top then.

You know, a really good part of this forum is that all the enthusiasm encourages a lot more attention to all this equipment.