soofoodude 6 #1 Posted April 25, 2017 Greetings - It's springtime in the northern prairie and I am fighting with my 520H. Five foot into my first pass of the season I got a medium sounding clunk, followed by a heavy, steady stream of blue smoke and loss of 95% of the power. I limped it back to the barn. Now, I can build you a house or a bridge - but significant wrenching is not my forte', so my very charitable little brother did a quick autopsy on it tonight and sent me the following photos. The engine still idles (with plenty of smoke) and has 680 hours. Other than regular oil lube & filters and blowing out the cooling fins from time to time, it has had no preventive maintenance (valves, etc.) or overhaul. I am thinking about a Honda or Vanguard Repower. Any insight from the real mechanics out there? 1 Share this post Link to post Share on other sites
ericj 1,576 #2 Posted April 25, 2017 didn't break the rod ? eric j 1 Share this post Link to post Share on other sites
soofoodude 6 #3 Posted April 25, 2017 (edited) Don't know. Only took the heads off tonight. No banging around - it idles fine , although I didn't let it run very long. No pool of oil on the floor, so I am assuming at this point the rod, crank and block are probably all right, but a lot of oil in the air filter case. Most of it on the outside of the air filter. My brother the mechanic suggested broken rings. You can slightly move the piston a smidge in the cylinder. Edited April 25, 2017 by soofoodude Share this post Link to post Share on other sites
6bg6ga 271 #4 Posted April 25, 2017 I'd buy it for parts 1 Share this post Link to post Share on other sites
W9JAB 156 #5 Posted April 25, 2017 Find a local small engine shop, not necessarily a Toro dealer. Honda or Vanguard Re-power, would be my last choice. Share this post Link to post Share on other sites
WHX?? 46,797 #6 Posted April 25, 2017 Have little bro tear the rest of engine down to see if it's worth saving. Its not much use the way it is anyway so you have nothing to lose. If not don't scrap it, savable parts are parts. You can get a kit for a drop in replacement with a Honda I believe but you will get an ouch when you see the price. A few guys have done a repower with A HF predator motor with good success. Threads with how to do can be found here on RS. 1 Share this post Link to post Share on other sites
Achto 26,566 #7 Posted April 25, 2017 I noticed that both pic's show the pistons are at TDC. Do both pistons move when you turn the crank? If they both move then I doubt that a rod is broken, you could still have a damaged rod though. It looks like your failure happened to the side in the first pic. Mass amounts of blue smoke is usually a oil burning issue caused by bad rings, same issue will cause oil to be forced out of the breather into the air cleaner. The nice carbon build up on the pistons shows that this was not an issue that has been going on for a while, it happened all of a sudden. My guess will be broken rings / damaged piston. Share this post Link to post Share on other sites
BESTDOGEVER 218 #8 Posted April 25, 2017 If you have oil in the air cleaner check the pressure relief assembly located on the front right side of the engine facing it alao the crankcase vents can get clogged that was one of my oil leak disasters on the 518h 1 Share this post Link to post Share on other sites
soofoodude 6 #9 Posted April 25, 2017 Holy smokes - Thanks for everyone's input. The Crank and rods are not broken. I had him turn the crank and the pistons moved together. He also mentioned it could be a collapsed piston? - Pics atttached. I've been scratching together a parts list & costs from onanparts.com on a rebuild. Option #1 - Total rebuild kit $1300 + machine shop work $200? + $350 gratuity to little bro Option #2 - Select parts (2) piston and rings kits $ 270 (1) Gasket set $ 190 Machine Shop $ 200? if i need rods add $ $200 If I need valves and guides $ 150 ? Throw in a carb & ignition kit $ 200 Labor gratuity $ 350 Ball park total $ 1600 Range + a lot of time That's why I was leaning towards a repower - might not have to worry about anything for another 20 years plus better fuel mileage - especially if I could get a few Benjamins out of the old onan. Share this post Link to post Share on other sites
Achto 26,566 #10 Posted April 25, 2017 2 hours ago, soofoodude said: Ball park total $ 1600 Range + a lot of time This could be an option for you. Less than half the price & not too difficult to adapt into the tractor. Plus MORE POWER !! I always like more power. http://www.harborfreight.com/22-hp-670cc-v-twin-horizontal-shaft-gas-engine-epa-61614.html 1 Share this post Link to post Share on other sites
WHX?? 46,797 #11 Posted April 25, 2017 The dealer drop-in Honda repo kit was right around 18 big bills with no labor if I remember right. Share this post Link to post Share on other sites
soofoodude 6 #12 Posted April 25, 2017 I've priced out three drop-in kits: 23 HP Briggs Vanguard $1,800.00 delivered Honda GX 630 (21 Net Rated HP) $2,180.00 delivered. Honda GX 690 (22 Net Rated HP) $2,515.00 delivered I mow about 4 acres with a 60" deck and pull a 60" tow behind - every 5 to 7 days until mid summer. Share this post Link to post Share on other sites
ericj 1,576 #13 Posted April 25, 2017 19 hours ago, soofoodude said: Greetings - It's springtime in the northern prairie and I am fighting with my 520H. Five foot into my first pass of the season I got a medium sounding clunk, followed by a heavy, steady stream of blue smoke and loss of 95% of the power. I limped it back to the barn. Now, I can build you a house or a bridge - but significant wrenching is not my forte', so my very charitable little brother did a quick autopsy on it tonight and sent me the following photos. The engine still idles (with plenty of smoke) and has 680 hours. Other than regular oil lube & filters and blowing out the cooling fins from time to time, it has had no preventive maintenance (valves, etc.) or overhaul. I am thinking about a Honda or Vanguard Repower. Any insight from the real mechanics out there? I may be on the dumb side here but it does't make sense to me that you were running and all of a sudden the made a noise and started pouring smoke. if it didn't trow a rod and it was me I would pull both pistons and rods and have the block mic and every thing checked out you may only need to put a set of rings in her and be back in business. Just had a thought, I was told one time that a 520 lost a cam bearing or something and broke the cam and destroyed the block. Have the top end checked for any problems before completing a rebuild. you may want to check around for a used onan, maybe cheaper than what you are looking at now. if you get a used motor to get back in the game you then can take your time to rebuild your current motor and swap in down the road when and if you more problems. it lasted 20 years or so and almost 700 hours, no reason it can't last that long again maybe longer. I've seen tractors with well over 1000 hours and heard of tractors with over 2000 hours. good luck eric j Share this post Link to post Share on other sites