benelliguymn 2 #1 Posted January 8, 2023 (edited) 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 1 Share this post Link to post Share on other sites
SylvanLakeWH 25,003 #2 Posted January 8, 2023 The 520 guys will be along to add their Share this post Link to post Share on other sites
mrc 752 #3 Posted January 8, 2023 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. 3 1 1 Share this post Link to post Share on other sites
wallfish 16,705 #4 Posted January 8, 2023 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. 1 1 Share this post Link to post Share on other sites
grinchsr 609 #5 Posted January 8, 2023 In my opinion any increase in air flow around an AIR cooled engine is worth it 5 1 Share this post Link to post Share on other sites
peter lena 8,399 #6 Posted January 8, 2023 @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 1 1 Share this post Link to post Share on other sites
WHX?? 47,827 #7 Posted January 8, 2023 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. 4 1 1 Share this post Link to post Share on other sites
lynnmor 7,204 #8 Posted January 8, 2023 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. 2 1 Share this post Link to post Share on other sites
Handy Don 11,791 #9 Posted January 8, 2023 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. 1 Share this post Link to post Share on other sites
Bill D 1,819 #10 Posted January 8, 2023 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. 3 1 Share this post Link to post Share on other sites
lynnmor 7,204 #11 Posted January 8, 2023 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. 1 1 Share this post Link to post Share on other sites
Ed Kennell 37,242 #12 Posted January 8, 2023 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. 3 3 1 Share this post Link to post Share on other sites
jay bee 886 #13 Posted January 9, 2023 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. 1 1 Share this post Link to post Share on other sites
WHX?? 47,827 #14 Posted January 9, 2023 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... 1 Share this post Link to post Share on other sites