TC10284 109 #1 Posted October 24, 2021 (edited) P220g on a 520-8. Does anyone know some general symptoms of valves that are out of adjustment, either from wear, or from adjusting them incorrectly? Trying to determine if my valves are misadjusted or it's something else, such as bad gas. Carb was cleaned twice and thoroughly. It idles fine, although makes an unusual idle sound compared to everyone of my others, goes to WOT alright, it's just a slight bit "poppy" at half throttle and then full throttle. Engaging the 60" deck, it acts like it chokes for a slight second and then picks up fine. Seems to smooth out after she gets warm. Will try to get a video tomorrow. Edited October 24, 2021 by TC10284 Share this post Link to post Share on other sites
lynnmor 6,775 #2 Posted October 25, 2021 (edited) If it is time to adjust or there is any doubt about adjustment, you should do that immediately. First thing to check is the compression, if it is low tight valves is one thing that can cause that. When you cleaned the carburetor, did you remove the welch plug and idle mixture screw and clean in there? Did you inspect and test the intake manifold? Didn't you replace the carburetor with a Chinese one? Sound can be different between model years, there were some minor changes in the muffler design, also internal baffles could be rusted. Edited October 25, 2021 by lynnmor Share this post Link to post Share on other sites
TC10284 109 #3 Posted October 25, 2021 (edited) 1 hour ago, lynnmor said: If it is time to adjust or there is any doubt about adjustment, you should do that immediately. First thing to check is the compression, if it is low tight valves is one thing that can cause that. When you cleaned the carburetor, did you remove the welch plug and idle mixture screw and clean in there? Did you inspect and test the intake manifold? Didn't you replace the carburetor with a Chinese one? Sound can be different between model years, there were some minor changes in the muffler design, also internal baffles could be rusted. I'll check compression just to be sure. No on the carb questions but will check it. Yes. The intake had come apart on one end near the rear cylinder if I recall. I found this when removing all of it to check/adjust valves to spec. I drilled out the rivet carefully (NOT bigger than the rivet itself - just enough to get it out) and used a bolt/nut to tighten it back down. Then resealed the entire outside of the intake using red gasket maker, which I have done for other intakes without issue. No, I have not replaced the carb on this one. It is the original. It honestly acts a tad bit rich, at least when it's "poppy". Yet, adjusting the idle mixture does not have much effect. I guess maybe I could bend the float down (I think that's right) a tad and see if that helps... Choking it maybe a quarter way eventually kills the engine. And otherwise when it lightly "pops", or when engaging the 60" deck, the exhaust is black. Otherwise, it is a little gray and smells kind of like stale gas. It does not smell like oil is burning, nor white like oil is burning. I filled it with fresh gas prior to testing it out. New NGK TR5 plugs also. Edited October 25, 2021 by TC10284 Share this post Link to post Share on other sites
TC10284 109 #4 Posted October 25, 2021 (edited) 89 PSI on the rear cyl and 80 PSI on the front. 609hr on the meter. Not too good. Edited October 25, 2021 by TC10284 Share this post Link to post Share on other sites
lynnmor 6,775 #5 Posted October 25, 2021 If it were mine, I would pull the heads and see what is going on. With the heads off you can decarbon, check valve seats for looseness and condition, and check the cylinder bores for size and condition. Share this post Link to post Share on other sites
Snoopy11 5,713 #6 Posted October 28, 2021 Kinda sounds like an intake valve... but that is just a hunch based on what you have told us... Really no other way to find out than to dig in... Don Share this post Link to post Share on other sites
TC10284 109 #7 Posted October 28, 2021 (edited) 26 minutes ago, Snoopy11 said: Kinda sounds like an intake valve... but that is just a hunch based on what you have told us... Really no other way to find out than to dig in... Don So part of it was my fault. The valves were adjusted improperly, but I did not run it more than 10-15min as a test. I was somewhat in a hurry and misread, and did a 0.010" stem to guide clearance instead of 0.0010 on intake. Second time around I did 0.0015 since I don't have a 0.0010 feeler. Exhaust I did 0.0025 clearance second time around. So first time the gaps were too big on both instead of too tight. Feel dumb about that. However, it ran like this prior to the valve adjustment. Correcting the situation did not improve compression. Edited October 28, 2021 by TC10284 Share this post Link to post Share on other sites
Snoopy11 5,713 #8 Posted October 28, 2021 Compression is relative to valves and piston rings. So... while you are adjusting valves, if there is cabon built up on the valve seat, fillet, or seat face, your adjustments may only be relative to the carbon... which is going to disallow you to get proper compression. Otherwise, I think you are looking at piston rings... Don 1 Share this post Link to post Share on other sites
TC10284 109 #9 Posted October 28, 2021 (edited) I'll dig some more into it as soon as I can. You think it could still be rings if it's not smoking/burning oil? Don't know what the previous owner did to it, but seems to have lower hours for much mechanical wear. Who knows though. Edited October 28, 2021 by TC10284 Share this post Link to post Share on other sites
Snoopy11 5,713 #10 Posted October 28, 2021 1 minute ago, TC10284 said: I'll dig some more into it as soon as I can. You think it could still be rings if it's not smoking/burning oil? Are you seeing a lot of soot at the muffler? I have seen compression rings go bad, but oil ring stay good, thus not burning copious amounts of oil, but not having compression. I would be more inclined to go the valve route, cleaning everything in chem-dip... before digging in to the bottom end, though... Don Share this post Link to post Share on other sites
Snoopy11 5,713 #11 Posted October 28, 2021 One suggestion I just got from a fellow gearhead buddy of mine is checking/replacing the head gasket... I would go ahead and buy one, and replace when you go in to look at the valves. Don Share this post Link to post Share on other sites
Snoopy11 5,713 #12 Posted October 28, 2021 14 minutes ago, TC10284 said: lower hours for much mechanical wear That throws a bigger wrench into the mix... since it has low compression. Definitely sounds like opening it up might be your best course of action. Don Share this post Link to post Share on other sites
lynnmor 6,775 #13 Posted October 28, 2021 I don't know how you arrived at the valve adjustment, but it is to be .005" for the intake and .013" for the exhaust. 1 Share this post Link to post Share on other sites
TC10284 109 #14 Posted October 28, 2021 1 minute ago, lynnmor said: I don't know how you arrived at the valve adjustment, but it is to be .005" for the intake and .013" for the exhaust. I was looking at this. I also compared it to this one. "Clearance (Stem to Guide)" on Dimensions and Clearances Am I looking at the wrong thing? Share this post Link to post Share on other sites
lynnmor 6,775 #15 Posted October 28, 2021 2 minutes ago, TC10284 said: I was looking at this. I also compared it to this one. "Clearance (Stem to Guide)" on Dimensions and Clearances Am I looking at the wrong thing? Yep, see page 2-1. 1 Share this post Link to post Share on other sites
TC10284 109 #16 Posted October 28, 2021 1 minute ago, lynnmor said: Yep, see page 2-1. Dang. Totally overlooked that. Thanks! Share this post Link to post Share on other sites
TC10284 109 #17 Posted October 29, 2021 Guess I'll have another project to work on over the colder days. Share this post Link to post Share on other sites
Snoopy11 5,713 #18 Posted October 29, 2021 18 hours ago, lynnmor said: .005" for the intake and .013" for the exhaust. "Bad word" Yeah, I totally overlooked that. Thanks, @lynnmor... my bad. Don Share this post Link to post Share on other sites
TC10284 109 #19 Posted October 30, 2021 (edited) On 10/28/2021 at 7:45 PM, lynnmor said: I don't know how you arrived at the valve adjustment, but it is to be .005" for the intake and .013" for the exhaust. I went back into the valves just a bit ago and readjusted to the correct specs. Now I'm right at 100psi on the front cyl and 120psi on the rear. Thanks for that! Can't believe I forgot those as I've used the correct specs before on my others... I also sprayed the intake valves with some carb cleaner. Not sure if that helped or not, but it cleared off some carbon build-up. It still runs kinda "poppy", but it seems to get better the more it runs. I'm much less concerned about the engine though at this point, now that I have better compression. Here's a video (it's hard to spot the exhaust in the video - sorry): https://photos.app.goo.gl/iJwKczJdacSnqJSV8 Edited October 30, 2021 by TC10284 1 Share this post Link to post Share on other sites
lynnmor 6,775 #20 Posted October 30, 2021 Now the compression is in the normal range, but it still doesn't sound happy. When you rotate the engine by hand, is there any unusual noise? Share this post Link to post Share on other sites
TC10284 109 #21 Posted October 30, 2021 18 minutes ago, lynnmor said: Now the compression is in the normal range, but it still doesn't sound happy. When you rotate the engine by hand, is there any unusual noise? No sir. I don't hear anything unusual when rotating by hand. Share this post Link to post Share on other sites
lynnmor 6,775 #22 Posted October 30, 2021 Can you get the engine to idle smoothly at 1200 to 1400 RPM? If so, maybe the noise is coming from a defective muffler. Try holding a sheet of paper where the exhaust will push it, does it hold fairly steady? Share this post Link to post Share on other sites
Snoopy11 5,713 #23 Posted October 30, 2021 How long did the engine run with misadjusted valves? Hopefully I didn't miss something here.. Don Share this post Link to post Share on other sites
TC10284 109 #24 Posted November 2, 2021 (edited) On 10/30/2021 at 5:25 PM, lynnmor said: Can you get the engine to idle smoothly at 1200 to 1400 RPM? If so, maybe the noise is coming from a defective muffler. Try holding a sheet of paper where the exhaust will push it, does it hold fairly steady? Yes, it holds fairly steady. What's kind of strange is that the "poppiness" clears up after about 10-15min of WOT. It's done that twice. Once before correcting the valves, and once after. Both times was doing some test stripes with the 60" deck. Again, the gas (maybe 1/4 tank) did smell a little stale, but it was mixed with a full tank of fresh. Although I've never had stale gas make it sound like that at idle. It honestly sounds and looks like it's running a bit rich. I was wondering if bending the float might help some? I can adjust the idle mixture screw, but that should just be for idling, whereas it seems rich all the way around. Edited November 2, 2021 by TC10284 Share this post Link to post Share on other sites
TC10284 109 #25 Posted November 2, 2021 On 10/30/2021 at 7:15 PM, Snoopy11 said: How long did the engine run with misadjusted valves? Hopefully I didn't miss something here.. Don At most, 10-15min. It basically sounded like this before I got ahold of it though. 1 Share this post Link to post Share on other sites
