1979 C-101 1 #1 Posted October 9, 2021 (edited) Hi all, K321 ran fine until a few weeks ago when it started running erratically at full throttle while mowing. Thought it may be the carb being dirty, I had a new Walbro so I put it on and same thing. Changed the plug and condenser. Then new points and set the timing with a timing light, no change. Put another coil and coil wire on, no change. I once had a similar problem and it turned out to be water in the gas so I hooked up a small tank I knew was clean and new gas, no change. I also noticed now the exhaust pipe and the muffler were glowing orange and there were some sparks/embers coming out of the muffler. Runs fine up to half throttle and muffler is not orange. Any thoughts would be appreciated. My next step is to pull the head when I get a gasket. Thanks in advance. Edited October 9, 2021 by 1979 C-101 Share this post Link to post Share on other sites
Snoopy11 5,714 #2 Posted October 9, 2021 20 minutes ago, 1979 C-101 said: Hi all, K321 ran fine until a few weeks ago when it started running erratically at full throttle while mowing. Thought it may be the carb being dirty, I had a new Walbro so I put it on and same thing. Changed the plug and condenser. Then new points and set the timing with a timing light, no change. Put another coil and coil wire on, no change. I once had a similar problem and it turned out to be water in the gas so I hooked up a small tank I knew was clean and new gas, no change. I also noticed now the exhaust pipe and the muffler were glowing orange and there were some sparks/embers coming out of the muffler. Runs fine up to half throttle and muffler is not orange. Any thoughts would be appreciated. My next step is to pull the head when I get a gasket. Thanks in advance. Definitely do not continue running in this condition. Kinda sounds like burnt valves... but as a point of reference, when is the last time you got the valves adjusted? Notice any pinging when it is running erratically? Don Share this post Link to post Share on other sites
Snoopy11 5,714 #3 Posted October 9, 2021 (edited) Just kinda sounds like a decarb, valve job (stem adjust & lapping), new gaskets (head, breather, intake), clean/adjust points, set spark advance is in order to make it run like new again... Don Edited October 9, 2021 by Snoopy11 Share this post Link to post Share on other sites
squonk 41,162 #4 Posted October 9, 2021 Try running it with the choke on a bit. Sounds lean. That new Walboro may be to lean as well. Never had luck with those. 1 Share this post Link to post Share on other sites
Snoopy11 5,714 #5 Posted October 9, 2021 (edited) 9 minutes ago, squonk said: Try running it with the choke on a bit. Sounds lean. That new Walboro may be to lean as well. Never had luck with those. I second that... definitely sounds lean... I would most likely attribute it to carbon build-up... burnt valves... lack of valve adjustment... things like that... You could play with fuel adjustments of the main jet... but that it more along the lines of tuning... once you know that there aren't any other looming issues... Don Edited October 9, 2021 by Snoopy11 Share this post Link to post Share on other sites
Snoopy11 5,714 #6 Posted October 9, 2021 3 minutes ago, squonk said: choke on a bit. We should add... that is not a permanent fix. You run it like that over the longterm... you gonna have other issues... Don Share this post Link to post Share on other sites
Snoopy11 5,714 #7 Posted October 9, 2021 (edited) 7 minutes ago, squonk said: new Walboro may be to lean I agree to a certain extent. Since this is an ongoing issue and he was having the issue prior to the WALL-E installation... I am thinking more along the lines of 'other than' when it comes to fuel delivery. Don Edited October 9, 2021 by Snoopy11 Share this post Link to post Share on other sites
Snoopy11 5,714 #8 Posted October 9, 2021 38 minutes ago, 1979 C-101 said: sparks/embers coming out of the muffler Could be carbon... Don Share this post Link to post Share on other sites
daveoman1966 3,752 #9 Posted October 9, 2021 Did you ever take off all of the engine tins? I'd suggest that MAY be one of the over-heating issues. Just a thought. 3 Share this post Link to post Share on other sites
1979 C-101 1 #10 Posted October 9, 2021 (edited) Oh, I forgot to say I adjusted the valves too. I'll add that to the post. No pinging, new intake and breather gaskets. How do I set spark advance? I first set timing with a feeler's gauge, no change, then with a timing light, no change. The Walbro had an adjustable main jet. I have two Kohler carbs that ran good on other K321's, adjusted them and no change. I have not been using it since I saw how hot it was. Fins are clean. Edited October 9, 2021 by 1979 C-101 Share this post Link to post Share on other sites
oldlineman 1,481 #11 Posted October 9, 2021 restriction in the muffler idno worth a check. Bob Share this post Link to post Share on other sites
Snoopy11 5,714 #13 Posted October 9, 2021 Sounds like valve issue... but you won't know until you dissect it... Don Share this post Link to post Share on other sites
1979 C-101 1 #14 Posted October 9, 2021 Thought of the muffler too, put on one from the other K321 that is different , same orange glow but there was a solid flame coming out of it. It only takes about two minutes of full throttle for either muffler to turn orange. Fuel pump, I put a clear hose on it and it was working fine. If it is the valves will it be obvious? Share this post Link to post Share on other sites
Snoopy11 5,714 #15 Posted October 10, 2021 I have been thinking on this all day. Have to tried to gravity feed the carburetor bypassing the fuel pump? (Kinda dumb thing to do it would seem, but might be worth the effort)... Is it looking/acting like this... (took me a while to find this video... sorry...) Don Share this post Link to post Share on other sites
Snoopy11 5,714 #16 Posted October 10, 2021 I see that you put a clear hose on... so you can see that the fuel pump is working... ignore my gravity feed diagnostic... you already know that... Don Share this post Link to post Share on other sites
Snoopy11 5,714 #17 Posted October 10, 2021 Here's what I would do. Do a poor mans valve job. Take the motor out. Remove the head poor water or solvent, such as marvel mystery oil in the intake and exhaust with both valves closed. If it leaks, you know that... you have a leak. Chances are, there is a good bit of carbon built up on the exhaust valve, causing the leak... Don Share this post Link to post Share on other sites
Snoopy11 5,714 #18 Posted October 10, 2021 (edited) As well, once you take the head off... you may visibly see that the exhaust valve is not closing... i.e.... you may not need to do a leak test... Don Edited October 10, 2021 by Snoopy11 Share this post Link to post Share on other sites
oliver2-44 9,764 #19 Posted October 10, 2021 (edited) If you have access to a leak down tester that could help point you in a direction. When you swapped mufflers and carbs did you notice if the valve stems had much carbon buildup? Edited October 10, 2021 by oliver2-44 Share this post Link to post Share on other sites
1979 C-101 1 #21 Posted October 10, 2021 9 hours ago, 953 nut said: Snoopy11, That video is exactly whit my engine is doing. Oliver-244, I did not think to look at the valve stems. 953 nut, one of the replies to "leak down tester" suggested to charge the cylinder with air while both valves are closed and listen for air in the carb and muffler. I did that and could not hear or feel any air. I pulled the head and there is plenty of carbon but the valves look like they are seating. Also, there was oil on top of the piston, it has been using oil lately. Tomorrow I will try Snoopy's poor man's vale job. I'll see if I can post some pictures as well. Thanks again to everyone! 1 Share this post Link to post Share on other sites
Snoopy11 5,714 #22 Posted October 10, 2021 18 hours ago, oliver2-44 said: valve stems Don Share this post Link to post Share on other sites
1979 C-101 1 #23 Posted October 11, 2021 (edited) Here are some pictures. I guess my pictures are to big so I could only upload four pictures. The last picture is of the exhaust, the intake has IN S and appears to be the same size as the exhaust. I did Snoopy11's test and after two hours the exhaust leaked very little but the intake leaked down completely within a minute. Snoopy11, what do you mean in your last message "valve stems"? I can tell you that through the outlet of the block the exhaust valve stem is not shiny or rusty, kind of grey in color. The intake valve stem is shiny in some places and has rust in other places. I got this engine at a junkyard to use while my original K241 engine was being rebuilt. This engine had been out in the weather for who knows how long with no muffler or carb. The exhaust valve was going up and down but the intake was stuck in the open position. The rust was on it at that time, I freed it up and it ran fine. That was six or more years ago and it ran so good I put the K241 on just to make sure it was good and decided to save it and put the K321back on with no problems until now. It does not look like the engine has ever been apart as the oil pan gasket has the original paint on it but the piston is stamped .003. Looks like I need a total rebuild, thoughts ? Edited October 11, 2021 by 1979 C-101 Share this post Link to post Share on other sites
Snoopy11 5,714 #24 Posted October 11, 2021 6 minutes ago, 1979 C-101 said: "valve stems" You want to make sure the stems are not burnt/carbon buildup, causing difficulty of valve movement... also want to check the seat face... Now, if you are short on cash at the moment, and aren't seeing any damage to the valvetrain (i.e. holes in valves, pitting...etc...)... you 'could' take the head, soak it in chem-dip... along with your valves, using scotch pads to further clean everything off. You might get away with one on this engine if you aren't seeing damage. Regardless... definitely need to soak that head... get it all cleaned up... Don Share this post Link to post Share on other sites
Snoopy11 5,714 #25 Posted October 11, 2021 By the way... you can create another post and put more pictures if you like... Don Share this post Link to post Share on other sites
