New Member looking for advice on 520h mod

[benelliguymn 2]

1990 520H and wondering if the mod of the pulley side sheet metal by perforations for engine cooling has been proven worth the effort and cost. Saw it on another 520h for sale on this site and got me wondering. Thanks in advance for your time.

 

 

I see by some of the responses below this has been a recurring topic so thanks to all that take the time to dig it up again  I have done what I consider normal maintenance on my 520 since I bought it new. I will possibly do some type of air flow improvement by for sure I will be focusing on blowing it out after each grass cutting. You all have been very helpful and I hope I can contribute after I do some learnin'

Edited January 8, 2023 by benelliguymn
clarification

[SylvanLakeWH 25,554]

 

The 520 guys will be along to add their 
 

[mrc 812]

hello benelliguymn,

 

    as a 520H owner with a vented belt guard i would say this to you:

 

1... really no cost as it is just your labor to remove the belt guard and make some holes.

 

2... letting that hot air escape is better than having to fix a valve seat that fell out.

 

regards

mike in mass.

[wallfish 16,995]

It certainly won't hurt it. My 520HC is only used for snow blower duties so the cold air flow gives some piece of mind. But, if it was to be used for summer time mowing it would probably get a modified belt guard. 

 

[grinchsr 627]

In my opinion any increase in air flow around an AIR cooled engine is worth it 

[peter lena 8,622]

@grinchsr   , @wallfish,  @mrc  , looking at the repaditive   onan valve seat problem , would make me stay away from them , on the other hand there  are many available  vented belt guard  pictures on this site  , related to that engine . metal  hole punch  availability  would make that  easy . https://www.bing.com/images/search?Index=66&ajaxhist=0&ajaxserp=0view=detailV2&ccid=Z0GUmYbz&id=0E8BD37E339C150B8F38843A7EA7793A4E435A6E&thid=. regularly use a failure problem point to plan an elimination  of that problem , change it , improve it , make it better , make the problem a strong point , eliminate a failure , only me , pete

[WHX?? 48,815]

Might not help but sure can't hurt.  I have cut out all of mine. Since two of them have cabs and are snow tractors a bonus is it let's warm air up in the cab. 

Cost was less than 10 minutes of labor while the belt guard was off for maintenance. 

[lynnmor 7,305]

Some years ago I guy on here did a study using a thermometer, he found no difference between front and rear cylinder temperatures.  My thought is the oil filter and temperature sensor blocking the air flow might be a problem especially for those that won't run the engine at high RPM.  Keep any buildup in the fins cleaned out, oil leakage or spilling in the filter area holds dirt.

[Handy Don 12,217]

There are too many 516, 518, and 520’s running for 000’s of hours without throwing a valve seat for this extra ventilation to be critical on a well maintained and operated machine, IMHO.

[Bill D 1,920]

I don't have a 520 but I know some people have installed a remote oil filter kit in their Onans.  Makes oil changes easier and less messy, and improves air flow across the rear cylinder.  Something to consider if you buy a 520 or any other Onan powered machine.

[lynnmor 7,305]

11 minutes ago, Bill D said:

I don't have a 520 but I know some people have installed a remote oil filter kit in their Onans.  Makes oil changes easier and less messy, and improves air flow across the rear cylinder.  Something to consider if you buy a 520 or any other Onan powered machine.

That would be a good improvement but there isn’t a lot of room to add the kit.  The remote filter was produced for installations where the access for service was impossible.

[Ed Kennell 38,166]

15 hours ago, benelliguymn said:

worth the effort and cost.

Really no cost involved.

Anything that increases the air flow across an air cooled engine has to be a good improvement.

A couple things I have noticed on many 520s.

1. the grommet seal around the oil filter is missing allowing the cooling air to escape before crossing the fins.

2. the oil filter base plate is seeping oil which is blown across the rear fins.   the sticky oil collects dirt and grass that clogs the cooling fins

3. my 520s are only used for snow removal and the heat that passes thru the vented belt guard is collected with a cab extension keeping the cab 30F warmer than the outside temp.

 

 

[jay bee 897]

Looks like everyone has the subject covered. I’ll just say  to   

It’s a pleasure to have you and I hope all your questions get answered. 

[WHX?? 48,815]

7 hours ago, lynnmor said:

 Keep any buildup in the fins cleaned out, oil leakage or spilling in the filter area holds dirt.

That pretty much nails it...