Yes. As the valve train components wear, mainly the valve face and the valve seats, the valve clearance goes away. Little to no clearance will make the engine work much harder and put out less HP. Result: Shorter overall engine life.

 

Thanks for the the come back i've got two of them so I guess i've got some work to do.
I've got the blower houseing off the 94 already I just bought it this summer my other one is a 89 . they both have 600 hrs on them . I,ve got a shop manual but is there anything in paticular I need to be careful of or look for that could cause me heart burn in
tackling this project . I'll need to get intake an lifter cover gaskets unless it has oring type . An i'm assumeing finding the timeing marks is fairly straight forword top TDC on the compression stroke is where it needs to be ? Are you a Onan dealer or parts supplier ? I was pulling the starter on this on this machine going to get it checked today
it wasn't ingaugeing an disengaugeing right . I've heard about the rear cyl over heating
an valve guide failures is why I pulled the cover to clean everything up . An thats when I thought if those valves need adjusting now would be the time .
So thanks for your advice an any help you might send my way .

George

 

Went to your site may need some parts someday . I got started on the ole girl today
but got distracted by a visitor an did not get too finish . But looks to me like I can adjust these valves without pulling the intake . I,ve got the cover off the front Cylinder
an it looks like it won't be a proublem the back one i'm not sure , what say you ? I got as far as rolling it up on TDC an I can spin the lifters with my fingers but did not get the chance to get the filler gauge out but it appears theres no clearence. So thanks for talking me into this project I believe it will pay off . I had noticed this tractor put off more heat than my 89 does so maybe tight valves could cause that ? But it will be next
so we'll see what the difference is . I sure hope I don't have to pull that intake to do the
back CLY .

 

Intake will have to come off to remove the rear valve cover. As shown in the pics below the cover bolt hits the manifold.

Remove plugs and shine a light down the plug hole while turning the engine over by hand until the piston is at the top of the stroke and both lifters for that cylinder are at rest. Book calls for .005" int and .013" exh. I set them a little tighter, .004" int and .010 exh.

Once done setting the clearance on one cylinder turn the engine over several times by hand again and recheck the clearance. Repeat on other cylinder.

If Onan made it so you could adjust the valves without removing the intake they would not sell as many 154-2495 int manifold gaskets. It's actually a good idea to pull the heads and decarbon them along with the valves and piston tops due to the fact setting the valves is much easier when you know exactly where the piston is.

You also get to inspect the condition of the cylinders, valves and seats while you are there. No downside to doing that.

 

Thanks again I was afraid you'd say that I'm at work an want get back to it untill
Monday. But I am surprized about pulling the heads i've pulled the heads on Two Stroke
motor cycles but no 4 strokes unless something else was wroung . Is this something
that needs to be done too make a Onan last longer . With 600 hrs on these machines
with no smokeing or oil useage I would think the cylinders are Ok. There are fuel additives that will help decarbonize if thats a issue on these flat heads. An i've been avoiding ethanol gas an treating all my gas year round .

 

Onan factory maintenance schedule is as follows:

P224G adjust valves every 500 hr's

P216G P218G P220G every 1000 hr's

Decarbon every 1000 hr's unless used continuously under light loads.

Checking valve clearance at 500-600 hr's on any model is still a good idea even if the book calls for waiting until 1000 hr's.

 

Thanks again for the info whats the highest hours you,ve seen on one of these 220's
when maintained by the book ?

 

4,600 hours before it was rebuilt the first time. Clean oil + Clean filtered air = long life between overhauls/rebuilds. Second rebuild at 8,100 hours and still going at close to 10,000 hours.

The original owner is a fanatic about maintaining it as the machine is what he makes his living with.

 

Let me ask, what is the hardest part of taking on the job of adjusting the valves? Is the process outlined well enough in the manual so that an average Joe with some pretty good experience with ODE and motorcycles can tackle it? I've got an Onan twin on a 1974 Suburban S/16, and I have no idea how many hours are on it, so it's no doubt in need of attention.

 

Well I guees I fall into the fanatic catagory too so if I can get any where near those kind of hours these machines will take me to the end of my mowing days . Hey speaking of clean Air do you use 30wt motor oil on your pre filter or a foam filter oil ? The way the
air comes out of the blower houseing right into the filter box it dozen't take long for it to
cake up . Which means its catching the dirt but at a certain point restricks air flow but
i've never felt like the power was down,but they really can go through some gas . I'm done with valve adjustment they wern't off that bad one intake .003 an a EXH .009
bwd theres nothing real technical about it an the the book is clear on things that matter
such as how to know your on the right stroke an both valves are closed . Other than that you have too take the engine cowl off an remove the exhaust an intake thought I was gonna get out of that until Onan man busted my bubble with the picture above . I sort of have a advantage since I have two 520H's so if i need two double check how something goes I can look at it . So even though shop manual has some good pictures
you might take a couple of snap shots if you think its nessasary . As far as the actual
valve adjustment itself You'll laugh or think Im not believing I had to take all this stuff appart to do something so simple all because of that one darn bolt . Onan man why couldn't a person put a stud with a nut in that rear position with a copper washer ?
You'll need intake exhaust an lifter cover gaskets an thats about it . I got mine from a local dealer but Onan man sales parts if I get to needing anything major I'll be giveing
him a call .