Duramax7man7 505 #26 Posted April 19, 2017 Yeah, The others came out fine except one that I was able to work out. This just wasn't having any of it. I didn't get it to move until the first nut I welded to it. But even at that it was only moving a tiny bit. I tried heating the surround aluminum a bit to see if that would help and nothing. I'm going to take a break from it for a few days as I have oral surgery today. 1 Share this post Link to post Share on other sites
Duramax7man7 505 #27 Posted April 25, 2017 Well after letting this whole situation sit a bit, had some other things that need attention, I picked up some nice bits and then decent tap set and was able to drill this bolt out and re-tap the hole as well as cleaned up the other holes. With through a few drill bits as the Drill Press was just to darn fast even on the lowest speed. Long story short I spent $56 on the tap set and another $12 on the new Cobalt bits for the job. So now it's off to the machine shop to get this valve issue fixed. Chucks Engine's in Westland, MI. is going to be machining out the old valve seat bore and matching up a new one that they will have. Everything for $80. So I'm excited to get that done and the engine back together and de-carboned to see how this engine really sounds in comparison to my 1990 P220G (2300hr+) being this one only has 1200hr+ on it. May not be much difference at all. still good to have progress. I'm gaining more wisdom about these with each step as well as the tool supply to get the job done. Looking at the engine block off of the tractor and it's actually really clean. NOTHING like caked up mess I found behind the flywheel of the 1990. This one doesn't have any oil seepage as well. Share this post Link to post Share on other sites
ericj 1,576 #28 Posted April 25, 2017 yesterday my cousin's daughter called me and said that one of the decks on their 520's had a blade come loose, so she tightened it up and it seemed to mow better for awhile. she then noticed it loose again, I told her to bring it up and I would look at it. A couple of later she pulls in the yard with the deck still under the tractor. so I proceed to check it out and found the bearing housing loose. now to get to the point. when I started the tractor up it didn't sound right. pulled the deck out and found bearing housing broken, back to the tractor, pulled the front plug wire and tractor shut off. pulled the back lug and no difference, started to look for another plug when decided to cut to the chase and run a compression test. found 110 psi on the front cylinder but only 40 on the back. tractor has a very noticeable miss at low RPM's but does smooth out at higher rpm's. the back cylinder is definitely firing becuase you can feel the heat in the exhaust. So now I have to pull the motor and check it out, another project that I don't have time for. I do have an 88 or 89 520 sitting out back for several years now that is my cousin's that I may pull the motor off and swap out till I can fix the other motor. time will tell. eric j 1 Share this post Link to post Share on other sites
Duramax7man7 505 #29 Posted April 25, 2017 Oh wow. Yea the compression tester kit is going to be my go to tool from now on. I couldn't get anything on my rear cylinder. But when the intake valve seat easily moves forward and backward I can understand why. I'm guessing that when at higher rpm's the compression stroke is so fast that the air can't leak out fast enough and the compression is probably simulated to be a little higher from the higher rate of compression when compared to the maximum rate at which the air leaks from the cylinder. If you're pickin' up what I'm throwin' down. Well maybe you'll get lucky and you'll just have major carbon buildup in that cylinder. If I may make a suggestion, make sure to work back and forth slowly to back out any tight head bolts with maybe even a few light taps on the head. The head bolt holes go right through to about the 5th or 6th heat sink so try spraying the inside of those holes with some BP Blaster as well while working out that bolt. Like I said, I snapped one of mine almost clean off at the head and it was a bear trying to get it out. Went through 3-4 welded nuts before deciding to try and use a back out. Fried a couple of drill bits making a hole for the back out and then busted off the cheap-arse back out in the head and had to drill a tiny diagonal hole from the outside of the head in between the 2nd and 3rd heat sinks to pop that sucker out. Then fried 3 more drill bits before deciding that my drill presses lowest speed was still to fast. In the end I went up to Sears and fired off of nice little entry set of taps, drill the hole out with a nice Cobalt drill bit in a Ryobi dual hammer drill/ drill on low speed and kept the trigger at about half way and dug in. Got all of the way through with a little oil and then tapped out the hole, removing old bolt remnants along the way. I'm going to get a half inch longer head bolt to ensure that I get a good amount of grab to avoid any future issues. Should be perfectly fine once back together after getting that new seat. Hopefully you won't have to deal with all that. Share this post Link to post Share on other sites
Duramax7man7 505 #30 Posted April 28, 2017 Off to the machine this past Wednesday... Should have it back middle of next week. Front Cylinder Rear Cylinder... Share this post Link to post Share on other sites
Tinbender 5 #31 Posted April 28, 2017 On 4/13/2017 at 5:43 PM, Mastiffman said: There is compression. How much Im not sure. But would it cause the engine to better with the plug out and wire off it that cylinder had low compression? EDIT: Coil Primary is good @ 3.1ohm but the secondary is registering @ 20,510??? Also the long 18" spark wire is at 1.54ohms and the new 18" on my 1990 520h is 4.59 ohms. The short one is 1.89ohms and the 1990 520h is 1.85ohms. So maybe a combo of the coil and the long spark wire? Im going to swap the coils and see if that makes a difference on the 1991 (recently acquired)... I just tested the new coil I purchased and it read 21,600 ohms both on a DDM and analog meters. 1 Share this post Link to post Share on other sites
Duramax7man7 505 #32 Posted April 28, 2017 That's good to know. I was going to test it on my other 520 to make sure. I'm excited to hear how it runs on both cylinders. I'll be taking off the oil pan and removing all of the sludge as well before reassembly. Share this post Link to post Share on other sites
Duramax7man7 505 #33 Posted May 3, 2017 Original rear cylinder with new valve seat. They did a good job. Adjusted both cylinders valve lash. Got the heads back on, intake and exhaust manifolds on as well. New head bolt on and head torqued down. Pulled the oil pan and seemed like a newer Onan gasket and ot still had some blue ish color to it.? Everything looks good inside. Pan wasnt even to sludgy. But cleaned it up completely and put the pan back on with new gasket. More to come... Share this post Link to post Share on other sites
Duramax7man7 505 #34 Posted May 4, 2017 Okay, So I got the engine back in and running yesterday. Sounds MUCH Better! Both cylinders running well. Haven't tested the compression but I will. It felt a lot better when turning the engine over by hand this time, after the valve and de-carboning everything and setting the valve lash. There is a little bit of miss though during idle and higher Rpms and it backfires at the exhaust when I drop from WOT to idle. AND After replacing all three (kill, switch and start) relays, I'm still unable to start the engine unless I either jump the starter or the brown wire to the dark blue wire on the switch relay. So ground connection cleanup is next as the tach isn't working at all either. A quick test of the ground from the fuse box was at 120hms. YIKES! So the steering tower grounds will all be cleaned up today and given a retest on function. Share this post Link to post Share on other sites
Duramax7man7 505 #35 Posted May 5, 2017 (edited) Got the grounds all cleaned up and still the same issue. Long story short. I tested the safety switches and found a bad seat switch and the Neutral safety switch needed some attention. Pulled that and reinstalled it a few times with no luck. Tested the switch with a DMM and it tested fine. Pulled the wires and connectors from the plastic molex plug and connected them and that did the trick. Put it back together and made sure the contacts were optimal and boom! It started! Found the tach light ground broken. Fixed that. I think that the tach is bad just like the 1990's. It idles at 3000rpms and then when WOT ramps to 4500+. Same thing that the last one did. Need a new Fuel level sending unit as the float arm came off. So a few things need some attention still but overall, making good progress. No leaks. Rectifier was bad at only 10.6v output. New on the way arriving Saturday. One thing off is the carb needs to be set to 2 turns out on the air mixture screw on the side of the carb. Normal is 1-1/4 turns out. So may need a float adjustment? Edited May 5, 2017 by Mastiffman Share this post Link to post Share on other sites
