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Rich16

Valve Adjust 520h

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Rich16

Hi All,

Looked on the site (and YouTube) and can't find anything comprehensive about adjusting valves without taking things apart - most are with engine removed I don't want to do.

Can you adjust the valves with engine on by just taking off the air cleaner unit to expose the valve covers and take the plugs out?

Can Top Dead Center be found without removing anything else or does the flywheel canopy have to be removed?

I've adjusted valves on cars, etc and it's easy and straightforward - but I don't want to have to take anything apart that's unneccesary.

Many thanks!

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WVHillbilly520H

Find the Onan engine manual(here in the manuals section) and download it. But usually the intake and exhaust manifolds are removed to make things easier to get to, while you're at might as well pull the heads and decarbon as well @richmondred01, just did one not too long ago I'm sure he can give you better details as I have yet to have my engine apart myself yet in 20 years of ownership.

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lynnmor

It is nearly impossible to do a valve adjustment with the intake and exhaust in place.  Even if you could, keeping dirt out of the engine just won't happen.  Like said above, pull the heads to decarbon, then check for loose valve seats, ask me how I know this.  Pull the intake and check the split for possible leakage and check it where the exhaust shield may be cutting into it.  Pull the muffler, glass bead then paint with high temperature paint, these mufflers are expensive to replace.

 

I go a bit farther and do a valve job and replace the intake valve seal while things are down.  I also open the carburetor, clean it out and adjust the float.

 

Use genuine Onan gaskets, especially the intake ones as the imported gaskets turn to mush.

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Rich16

Appreciate the comments and now I know what I'll be getting into.

Pretty major job and it's running great but has around 650hrs and I know from above what happens if you don't do all of this.

It's kinda crazy but the manual says 'Remove all parts necessary to gain access to valve tappets' - not particularly helpful.

This forum is terrific!

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