1973Auto 80 #1 Posted December 27, 2023 (edited) Hey all. K301 12hp, starts fine but doesn't sound right and the exhaust pipe gets cherry red hot and with a little playing with the throttles it goes back to normal sound and works fine. Pipe cools and all is good. What do you think is happening and what should I do to try to prevent this in the future, thanks!! Edited December 27, 2023 by 1973Auto Spelling Share this post Link to post Share on other sites
Jon Paulsen 291 #2 Posted December 27, 2023 Sounds to me like the exhaust valve is sticking open. If so, you would need to open up the case to resolve it. 5 Share this post Link to post Share on other sites
Ed Kennell 41,800 #3 Posted December 27, 2023 Pull the head and check the exhaust valve for closing. It may just need a decarbon. 6 Share this post Link to post Share on other sites
oliver2-44 10,689 #4 Posted December 27, 2023 Add some Rislone treatment to you oil and add some Marvel mystery oil to your gas to help lubricate the valves. Pull the head and describing as others have said. 2 Share this post Link to post Share on other sites
lynnmor 7,799 #5 Posted December 27, 2023 A lean fuel mixture can cause high exhaust temperatures, so clean out your carburetor and see if that solves the problem. 6 Share this post Link to post Share on other sites
953 nut 59,784 #6 Posted December 28, 2023 First thing to take a look at would be the muffler. If something has broken loose inside it could be blocking the exhaust flow then falling out of the way allowing normal engine operation. Share this post Link to post Share on other sites
leabassett@sbcglobal.net 156 #7 Posted December 28, 2023 Also look at the points My old Harley needed a points adjustment every time the pipes would turn red at night. 3 Share this post Link to post Share on other sites
rmaynard 16,290 #8 Posted December 28, 2023 A lean fuel mixture (too much air) can cause a red hot muffler. Older carburetors that have had a lot of use can develope wear at the throttle shaft causing too much air introduced into the carb. This is evidenced by having poor running conditions that can't be adjusted out. Usually though the problem does not go away on it's own. I'd pull the head and see what the exhaust valve is doing. Remember, you have ACR which will keep the exhaust valve open slightly. 1 Share this post Link to post Share on other sites
1973Auto 80 #9 Posted December 28, 2023 Took the head off last night. Had some brownish hard carbon chips around the valve head. Had a good amount of carbon built up on the other and the head. Scrapped it all off and gave it a rub with Scott Brite pad. Looking like factory new 🤣. Drained the oil now need to assemble tonight. Thanks for the advise! 1 1 Share this post Link to post Share on other sites
Jon Paulsen 291 #10 Posted December 28, 2023 Awesome! it sounds like you nailed it down. 1 Share this post Link to post Share on other sites
