My son and I just finished putting our Manco Thunderbird back together. I scrounged up a Tecumseh 3hp from an edger. It's been working well, but today it started "bucking" under load. It idles fine. When you pull away from a stop it's fine for the first few seconds, but it then starts shaking quite a bit until your up to cruising speed. It doesn't seem like a misfire. Bucking is the best word for it. We had a 5hp B&S that did the same thing. Any ideas?
when you hit speed if you make it work hard like a hill does it act up again? is could be a dirty carb that has a dead spot. or another is the plug may be shorting out just enough to let it run but under load it act up and causes your shaking . what i would do is if your sure the clutch is good is change the plug and test then clean the carb and try again .if it still does it the look at your coil it may have weak spark .also do a check for vacuum leaks they can cause strange things like that to happen .
Neighborhood's pretty flat, so it's hard to find a hill to test it out on. I'm going to change the plug for good measure. I doubt there's a vacuum leak, as the idle is smooth. I'm kind of assuming it doesn't have points, but I'm not certain. The problem is it just doesn't feel like a misfire. It's more like a violent thrashing between say between 5 and 15 mph. The strange thing is our go-kart with a 5hp B&S started to do the same thing after we had it a few weeks.
almost sounds like the gearing is wrong?but the factory sprocket is big and shouldn't do that,unless you change it with a small sprocket and with a low hp motor it will shake unit the clutch is lock up. something like the baja DB bikes do.......
also if the the clutch was trying to lock up at low rpm's that might cause a problem,but you said it was a new clutch.
maybe a good video of it doing it might help use:shrug:
maybe a good video of it doing it might help use:shrug:
Like I said; that's what it was in my case. I had a hilliard extreme duty. I put a max torque in and it solved the problem. I also ordered new bushing and sprocket for hilliard. I think it was the bushing because the key had some wobble on the shaft. I'll report back when I rebuild the clutch which component was responsible. Just curious. What clutch you have?
You should clean it.. They get oil and road dirt and clutch dust in them that burns onto the clutch drum and shoes and it is sticky.. So instead of the shoes slipping by as it's trying to tighten up.. It sticks to the drum and grabs really hard.. I would use Break Parts Cleaner to thoroughly clean all of the internal parts, then use some kind of transmission fluid or bushing lube (just a drop or few) to lube the bushing that the drum rides on... If it is the clutch, the clutch springs or shoes are not damaged, that should fix a problem clutch.....
Although I have heard that Hillard clutches act ridiculous just because of their design if you have one of those... The weights are weird and 4 piece with a goofy spring so the weights can't come out and slip smoothly, they tip to the side as it's contacting and pulling the drum and they will chatter...
Although I have heard that Hillard clutches act ridiculous just because of their design if you have one of those... The weights are weird and 4 piece with a goofy spring so the weights can't come out and slip smoothly, they tip to the side as it's contacting and pulling the drum and they will chatter...
OldDinger bought one brand new, used it for like ten minutes, then hung it in a tree and shot at it with a rifle... He was NOT very happy with the clutch.. If it's brand new it's probably not gummed up, thats something ya get after lots of miles and use... I would suggest a Max Torque clutch for the price and use-ability.. If you still have your old one I would say clean that one all up good and try that one again..