Strokerace2639 0 #1 Posted 2 hours ago Yes I understand there are many threads about this. As they as a few years old, and I just picked up this machine I am starting a new. 1988 Wheel Horse 520-H bought from original owner. only parts I have replaced to this point are the Fuel Filter and the starter solenoid. Runs great on start up and until its good and warm ( 15 minutes or so), then it starts surging/hunting. The engine speed goes up and down, the vacuum goes from like 2 to 15 very rapidly, under load. As soon as I stop the mower deck it settles right back to what I would consider normal. Sets already done. used propane and starter fluid around the intake and carb. found no noticeable changes. i did notice the fuel filter never seems FULL. is this normal? What are the things I should look at and in what order? Thank You, StrokerA Share this post Link to post Share on other sites
sqrlgtr 2,984 #2 Posted 2 hours ago (edited) just acquired a 520H a few months ago same symptoms and the 2 piece manifold was leaking/sucking air. Replaced manifold and runs like a champ now. I did clean/rebuild carb while I had it apart also dun a good cleaning of engine cooling fins whist I was in tare down mode...Oh yeah had a bad oil leak at oil drain where it goes into block. Just some well needed love and ready for another 30 years A few pictures for encouragement/courage Edited 1 hour ago by sqrlgtr Share this post Link to post Share on other sites
sqrlgtr 2,984 #3 Posted 1 hour ago Almost forgot Welcome to Share this post Link to post Share on other sites
Ed Kennell 46,150 #4 Posted 1 hour ago (edited) 1. clean the carb 2. clean the carb 3. clean the carb to the Edited 1 hour ago by Ed Kennell 1 1 Share this post Link to post Share on other sites
953 nut 66,384 #5 Posted 57 minutes ago Perhaps a vacuum hose has a small crack which is aggravated by the vibration of the mower deck. Share this post Link to post Share on other sites
