Noobs first tech post- 520H- diving in

[Greentored 3,220]

Picked up my first red, a 91 520H a week ago and it took about 10 minutes to realize this is going to be another addiction. 30+ years of hotrods and old motorcycles, I cant seem to leave anything as is, I gotta ***k with it and try to make it better.

Ive done a bunch of online searching, learning all I can about that P220G and sounds like if its maintained and kept cool, it will last a long time, which brings me to this- whats the scoop with the air cleaner picking up forced, hot air through that tube leading into the tin shroud, and can I block that off and run an open style element? Pretty sure Onan knows what theyre doing, but seems this would be a win/win- cooler intake charge, more air delivered to cool the cylinders and heads. Thoughts?

[doc724 925]

Not for certain, but I think this is the crank case vent.  If you can remember way back in the 60's before air quality became a consideration, automobiles had open crank case vents.  They were always puffing out smoke down towards the ground.  By the 1990s, small engines (I think) had to do some emission mitigation.

[wallfish 18,080]

That tube comes from the blower housing so it's not hot air, since the air is directly from the intake of the flywheel and before it passes the engine. Not really sure what the purpose is though. Just recently got my first Onan powered 520 so I'm also interested in it's purpose.

 

My Kohler powered tractor does have the intake tube pull air from the warm side tins for winter or cold conditions but it can be rotated for warm conditions. I assume that's to stop the vaporized fuel from freezing

Edited December 18, 2019 by wallfish

[WHX?? 51,732]

Green

Lots of 520 experts here and I wouldn't have three and always looking for another without their help!

Always thought that tube was to keep a positive pressure in the air cleaner housing to try and keep grass clippings out???   So what keeps it from blowing snow in there when blowing??? Briggs did the same thing with some of their motors.

I wouldn't see any issue with blocking it off for more cooling to the jugs. Onan flywheels move a pretty decent amount of air. The thought around  here Green is to open up the belt guard around the back cylinder to help better cool it and avoid the dreaded valve seat issue. We don't know if it helps put sure can't hurt.  I know @Ed Kennell even put a duct on his to get heat up into the cab.

Edited December 18, 2019 by WHX24

[Greentored 3,220]

32 minutes ago, doc724 said:

Not for certain, but I think this is the crank case vent.  If you can remember way back in the 60's before air quality became a consideration, automobiles had open crank case vents.  They were always puffing out smoke down towards the ground.  By the 1990s, small engines (I think) had to do some emission mitigation.

Oh, Im quite familiar with the crankcase vent, road draft tubes on the old vehicles, and the old mans 317 deere in which that old KT17 kohler blows oil and smoke out of like a locomotive haha. This tube is maybe 1.5" diameter- the fellas above are talking about it.

[Lee1977 7,194]

I think it was a designed for motor homes generators as they are always enclosed in tight spaces on the side. I think it's there to insure the engine gets enough intake air.

[lynnmor 7,813]

The tube from the shroud to the air cleaner is there so the flywheel acts like a centrifugal air cleaner.

 

I know that many open the belt guard, and it may help, but air is forced thru the fins regardless.  Keep the fins clean and the grommet around the oil filter in place and you should be fine.  I have four P220G engines and the only one that had a loose valve seat was a junker with mud dauber nests, missing oil filter grommet as well as complete and total neglect.

[Pullstart 66,690]

 @Greentored!  I have zero Onan or 520 experience, so I only stopped by to say hi!

 

 

[peter lena 9,252]

greentored , glad to have you on board and getting after your horse, i like the rear  cylinder vent area , vital to fend off the valve seat problem area, i would recommend you look for some  PERFORATED ALUMINUM ,or light steel at your local metal source for a  flow thru guard on the area. you are in the right place for feedback and insight to make things better, have a good Christmas , pete  

[Ed Kennell 41,913]

Here's the heat collector Jim @WHX24 mentioned.   The belt guard is vented and the cab stays 30F above outside temp.

 

Like stated above, keep the fins clean and the oil filter/tin seal in place and with the opened belt guard, the rear cylinder should not overheat.

When you take the tins off to clean the fins, look for an oil leak under the oil filter mounting bracket.  It is fastened to the block with two bolts and has a very narrow sealing gasket.

If this drips oil, it is blown  across the fins and makes a sticky mess that collects grass clippings clogging the fins.

Enjoy the 520....she is a snorting monster.

[Daddy Don 909]

[Greentored 3,220]

I do plan to open up the belt guard area and order a gasket for between the shroud and oil filter- couldnt believe how much air comes out around there that would otherwise be directed across the cooling fins. Summers here in NC get plenty hot and although theres only an acre to mow, I have a feeling this ol girl will also be putting in a garden, pulling stumps, dragging firewood, cleaning ditch lines, etc....  shes gonna get used!

Thanks for all the replies- good group of folks!

[Lee1977 7,194]

Good to have you on Redsquare. I not quite you neighbor, I'm about 6 miles East on China Grove and Landis.

 

 

[tom2p 2,394]

some RS members did these cool mods: 

 

 

 

 

 

 

Edited December 19, 2019 by tom2p

[Lee1977 7,194]

I went a little further as you don't need the belt guard on a hydro like you do on an 8 speed. It's required to help stop the belt on an 8 speed for changing gears.

 

[Greentored 3,220]

Rockwell, yep not far at all! Got any red stuff for sale over there?  Haha