Onan valve adjust and more.

[WheelhorseBob 1,550]

Last project this weekend. I’m adjusting the valves on my 416. Doesn’t seem like a bad job at all. I also have head gaskets to do a decarb but that will wait. Weather windows can close fast this time of year in NH and I don’t want this dead in the water for too long. Question for Onan guys. Reseal the intake or no? It ran well but was ticking so the valves are a must but.....

[Handy Don 14,061]

Hi. Just did over a P218 and elected NOT to disassemble and reseal the intake manifold.  It was a 400 hour engine, I saw no sign of deterioration. I taped over the ends and put a bit of gasoline into the manifold while it was off the engine and couldn't detect any seepage out of the seams, either.  I cleaned it and put it back.  

The only step I nearly forgot was too put back the spring "reed" valve in the front cylinder valve cover (a sort of PCV system.)

Also, following the manual and advice from members here, was careful to use proper torques on ALL bolts and nuts (the valve covers seem barely more than finger tight!) and to trim a bit of the manifold cover where it was rubbing on the manifold.

[WheelhorseBob 1,550]

Reed valve in front valve cover? Mine are identical?

Edited January 10, 2021 by WheelhorseBob

[Handy Don 14,061]

5 minutes ago, WheelhorseBob said:

Reed valve in front valve cylinder? Mine are identical?

Sorry for the false lead. Clearly the P216 doesn't have the reed-valved PCV tube that on the P218 connects from the top of the front valve cover to the air cleaner.  

You're good!

 

[lynnmor 7,814]

Do the check with gasoline in the intake.  I clamp a plate with gasket material over the carb hole and then pour gas in.

 

See that small cut in the side of your intake?  Trim the heat shield there and look for other cuts as well.

 

The breather design changed over the years, the one that goes in a valve cover has a hose that is troublesome.

[1995 520H+96+97 937]

Run a end tap in the intake and exhaust bolt mounting holes. New bolts with never seize  and gaskets also. 

[richmondred01 2,307]

Every onan I get in I pull the engine, decarb and remove valves clean carbon and adjust.

That way you know that your starting off fresh because most have never been done. 

Thats for an unknown engine. All others every 500 hours. 

This one just came off the bench. 
It has 550 hours and has been very well maintained. Minimal carbon build up. 

Edited January 11, 2021 by richmondred01

[c-series don 10,023]

I remember as a kid watching an old mechanic drip, not pour water into the carburetor of a car running at probably 3/4 throttle. He explained to me that it would decarbon the pistons and valves. I remember lots of smoke. Not sure if anyone else has done or heard of this before but I wonder if you could do it with an onan? Again DRIP NOT POUR. We all know what will happen if you pour water into a running engine! 

[richmondred01 2,307]

5 minutes ago, c-series don said:

I remember as a kid watching an old mechanic drip, not pour water into the carburetor of a car running at probably 3/4 throttle. He explained to me that it would decarbon the pistons and valves. I remember lots of smoke. Not sure if anyone else has done or heard of this before but I wonder if you could do it with an onan? Again DRIP NOT POUR. We all know what will happen if you pour water into a running engine! 

yep did it in the flatheads. 
 

[Tuneup 1,452]

I've just finished the valves on my very early P216 - it has the vent filter on the front valve cover but does not have an oil filter. Just for the record - seems the lister has his question answered .

Question: What method do y'all use to remove the carbon from the head? This is aluminum and the old wire wheel is a no-no. I've looked for brass but am out of luck. I'm down to hand scraping with an old brass windshield scraper. Help?

[richmondred01 2,307]

Angle a razor blade at 45 degrees so it won’t dig. That gets the big stuff.
Use brake cleaner and a  soft cup wire brush on an 1/4 angle grinder. That will take 95-98 % off.

Finally use scotch bright to remove the rest.  

[Tuneup 1,452]

Thanks!!!

[lynnmor 7,814]

3 hours ago, Tuneup said:

I've just finished the valves on my very early P216 - it has the vent filter on the front valve cover but does not have an oil filter. Just for the record - seems the lister has his question answered .

Question: What method do y'all use to remove the carbon from the head? This is aluminum and the old wire wheel is a no-no. I've looked for brass but am out of luck. I'm down to hand scraping with an old brass windshield scraper. Help?

I have used oven cleaner successfully on the heads, the low odor kind will let you use it indoors. The oven cleaner can discolor aluminum, so wash it off  before it is on too long.   I don't use any kind of metal tool to prevent damage.

When scraping pistons, I oil the cylinder walls and move the piston to the very top.  After cleaning, the oil will hold the dirt as you move the piston down a little.

[pacer 3,177]

All carbon on heads is not created equal Some times its like cement and others comes right off. If its the softer kind a stick of hard wood (like oak/hickory) shaped like a paint paddle with a chisel type taper sanded on end will do the trick. Other wise the already mentioned methods will have to be used.

 

On the manifold leakage, I fabricate a plate to fit/cover the carb mount and mount it in the vise upside down then fill with .... whatever, paint thinner, gas, kerosine, etc and let it sit while I do the other maintenance. So far I've never had one to leak --- which suits me just fine!

[tom2p 2,394]

hard plastic scraper might work to remove carbon ?  

 

probably around 40 years since I decarbonized a head or piston - but I think back in the day I did use a wire wheel on a drill or dremel ... ? ... didn't know any better 

 

[squonk 43,794]

Soak the carbon with carb cleaner, lacquer thinner or Sea Foam. A good amount of carbon will wipe away.

[Tuneup 1,452]

I appreciate y'all, thanks - will try each and every one of these methods, just for comparison. Makes me curious. The rings are on their way so I'll have this engine together by month's end.