fourwheels0 191 #1 Posted November 7, 2011 what should the max rpm's be on a 1989 520h with 20hp onan? mine is 3200-3400 cold and then 3500-3700 warmed up. also should the rpm's go up when driving from flat ground to a downhill area?. mine goes up to 3800 or so then comes back down pretty quickly. like when the hydro has a load on it then free wheel's a bit before slowing the tractor back down. my engine temp seems to be around 230-250 (checked with a raytec temp gun)when warmed up. is that normal?. i'm not too familiar with these 520h's. thanks Share this post Link to post Share on other sites
SAM58 30 #2 Posted November 7, 2011 WOW, That is fast... I have no trouble mowing with a 48" deck @ 3200 RPM's max. I do not run mine any faster than 3200 - 3300 RPM's The faster you run it the hotter it will get, heat is a killer... thought to be the reason for valve problems with the 20 HP Onan's. Mine also speeds up a little down hill. I have a temp gun similar to yours and my 520 is at around 190 - 210D after running it for awhile. Make sure you keep it clean so there is plenty of air flow though the engine cowl. I am sure there are other here that can give you more insight, I have only had mine since Feb. this year. Share this post Link to post Share on other sites
fourwheels0 191 #3 Posted November 8, 2011 the 230-250 temps were the hottest spots i saw. avg i guess was 210 or so. so i guess it's running around the right temp. it seems to have good airflow through both the front and rear of the engine. all the fins look good and clean. i did get some stuff out of the rear fins when i washed the air hosed it off. Share this post Link to post Share on other sites
