[doug_cartwright]

They are more of a plastic cover, not a screen on the 420/430.

 

[artfull dodger]

I am going to be running a rear finish mower and not a belly mower on my 420. I may just retro fit the flywheel grass screen on my Onan before spring mowing gets started.

 

[TempletonJDguy]

I’m in the no belly screen, keep your engine clean, camp. Seen way too many screens with an inch of insulating debris and damaged engines.

 

[artfull dodger]

Thats from guys not doing the maintanice of keeping the screen clean. The screen is there for a reason, since most engines lack the flywheel screen on them. I do plan to add a flywheel screen as its easier to find than the belly screen.

 

[TempletonJDguy]

I also don’t see adding a belly screen if the insulation from the hydro pump to the rear of the tractor is missing. Just a massive hole in the same area. I have a good friend that just added a fan to the front of his tractor. Now this is not for the safety campers as it would surely take fingers if you blindly stuffed your hand in the running tractor. Still waiting on engine temp differences before and after though.

 

[artfull dodger]

Keeping up with any oil leaks, valve adjustments and just generally thing clean and free of chaff or oily gunk should be common sense up keep. But its not for the majority of owners, even those owning multi thousand doller ZTR's that I used to service for a living. Then they cannot understand why the motor is burnt up at 1200 hours or smoking.

 

[TempletonJDguy]

I can’t agree more! Engine maintenance is just as much fun as running them, in my garage anyway. Maybe that’s why I have a 420 with 2900 hrs that’s my daily driver.

 

[TempletonJDguy]

With no bellyscreen 🤣🤣

 

[artfull dodger]

As long as you keep the engine clean and the valves adjusted, Onans last a long time. Also keeping the rubber grommet around the oil filter helps keep that side properly cool, with it missing, you loose alot of cooling air around it and that side will run hotter. With only 334 hours on my 420, she has a long life ahead of her.

 

[TempletonJDguy]

Yes I bought 5, then 5 more then the last time I got 10. From Cummins thier under 4$ but other sources are 12 & up. I’m super convinced that side of the engine runs hotter with the oil filter, oil sending unit, blocking some of the airflow that there’s no way on earth I’d run it without the oil filter seal! I’ll see if I can find a pic of that fan just for kicks.

 

[TempletonJDguy]

So unfortunately I only have a screenshot of a video my friend sent of his restored 318 with fixed front fan. This is just an experiment and real numbers will come in this summer, with and without, temp differences. Obviously this modification has serious safety implications and I’m not recommending it.

 

[Mike_U]

Artful - I agree with your efforts. Keeping a belly PAN in place on a 420 is a good practice in my opinion.

My 317 has a belly screen. Cooling air enters the tractor from down below because it is a closed frame machine and the only way to get air into the engine is from the bottom of the machine. The screen keeps grass clippings from getting sucked up and into the engine by the engine cooling fan. Yes, it is a maintenance item called out in the operators manual. I check it periodically and with no oil leaks, it rarely needs to be removed to clean it. If the machine is well maintained with no oil leaks, the screen maintenance is minor. If the screen is oily, yes, it can clog but that's a sign the oil leaks need addressing. I can see why some folks have engine issues when they go years without cleaning the screen and ensuring a good source of cooling air for the engine.

The 420 is an open frame machine and it has a solid plastic belly PAN, not a screen. Every technical info piece I have read said the solid belly pan allows the engine fan to pull clean air in from the rear of the machine past the hydro cooling fins and then into the engine compartment. I know others run without the belly pan on their open frame tractors without issues but I like the idea of air being pulled in from behind and flowing past the hydro fins to keep it cool. I also liked the idea that the belly pan tended to keep loose grass clippings from getting pulled into the hydro cooler and clogging the cooling fins. Every couple years I dropped my 420 belly pan to inspect for debris and oil leaks and I always solidly fastened it back to the bottom of the frame.

I also agree with keeping good firewall insulation in place, utilizing the oil filter seal and periodically inspecting the engine fins to make sure they are free of debris.

Good luck in your search. Hopefully you can find a good 420 pan close to your location.

 

[artfull dodger]

Thanks Mike, The fan at the front of that 318 is a bit strange. If your running the Onan at full power, which is what you should be doing if its doing work, then there is little to no need for that fan. There should be lots of air blowing out the grill if everything on the other side of the firewall is clean so that air can flow.

 

[N2 Tractors]

I would think a light duty 12v shrouded/encased electric fan with adequate CFM to move the hot air out the front would make more sense than a non shrouded little fan on the front PTO. Be interesting to see the numbers of the temp results with and w/o that fan.

 

[artfull dodger]

Considering the amount of air that an Onan moves at full throttle, there is ZERO need for any type of fan between it and the grill...period. The problem arises when folks are not keeping things clean, not adjusting valves or have a lean carb or most importantly, not running the engine at full 3600 rpm while doing ANY kind of work. I cannot stress that enough as a 30+ year small engine technician with factory master tech certification for all of the major engine brands including Onan. Folks seem to think that running at a lower rpm creates less heat, but the opposite happens, there is not enough air movement by the flywheel to cool the heat that is being made, so the engine gets much hotter than it would if the operator was running the engine at full power. Checking the RPM's(no load and under load) is something that is part of every full service I performed. If its off, either to high or to low, it gets adjusted so I see 3600 with the PTO engaged. And usually no more than 50 to 100rpm higher with the PTO off. A bit of overspeed with no load is required so that it falls back to 3600 under a load or darn close to it. While I have a laser reading temp gun, I plan to put a gauge that gives me cylinder head temps on both cylinders of my 420's Onan P220. This way I can see how things are going while mowing or at a plow day. With the cost of doing any major engine work going up and up, better safe than sorry. I have a small crack in the hood at dash end from an overly tight hood latch(PO did this not me), so I am going to put a small twin gauge pod there with oil pressure and cylinder head temps, That will hide and reinforce the crack area so it does not spread any more, and give me some needed engine info. The paint is to nice to have the whole hood redone at a body shop to fix the crack right now.