Tim : Have you checked your fuel filter ? Sounds like it starving for fuel while under load Bro !

hi ewalk,

thanks for writing. I don't doubt your diagnosis. Is that a common problem with older 4 strokes? What bugs me is that it runs so well in neutral but not under a load. Seems to me if the fuel filter is plugged it shouldn't run at all, no?
Tim

Tim : There are a multitude of potential issues . You may even have a head gasket leak causing compression loss and loss of power while under load which stalls the engine . The fuel filter is the easiest to visually rule out or compressed air restriction test , along with a base compression test . Does it backfire at all ? This would indicate a lean mixture condition . Even the governor control may require adjustment . There are numerous experts who I hope will jump in to your assistance , since I have not worked on any of the Older B&S let alone Tillers . There may be a form of disconnect switch on the Tiller Drive causing the stall since you have stated it rev's up fine without load from idle . Anyhow I will beg off this one and let the small engine experts guide you along the trouble-shooting All the Best Bro ! :)

thanks again ewalk. I appreciate your response. There is no backfire. My motor has fuel pipes screwed into the carb so I guess it's back to pulling the carb off and starting from there. I'm a bit over my head here but it's fun learning... I've got a decent parts diagram so I can find everything well enough. I read somewhere this morning that a fuel tank cap that's clogged might also be the problem as it creates a vacuum which mimics an empty tank. It's never occured to me to check a fuel tank cap. So you're right, lots of items on the list to check before a trip to the shop,

thanks,
Tim

Simple enough to verify Tim , loosen the gas cap and see if anything changes . I would 1st see if it stalls out when you let it idle for an extended period of time . Previously you indicated it was ok until you engaged the tiller drive . Heck no biggy use the kiss principle 1st I always say lol :). Hopefully Mouwnie or Baymee or Rusty will chime in their the Tiller / Tractor Guru's onboard !

WOW!! 1975! Used every spring and summer! Groan! I'd think its time for a new engine! Don't buy one of those tin tillers as sold by Sears, or others! They crap out in a couple years! Buy a new engine! And use the old machine, as the new ones aren't worth the money!
JMHO: Rusty Jones

Doesn't that model use a diaphragm on the side of the carb? Small rectangular plate with 4 screws? My first inclination would be to open up the main jet screw or change that diaphragm before going any further.

A weak spark will also cause the engine to die under load. There is more fuel in the combustion chamber under load resulting in the spark not jumping the spark gap.

thanks baymee and ddd_fredericks for those helpful suggestions. Yes, my engine has that plasticky diaphragm for pumping fuel. I've had that apart before but have not ever replaced it. Perhaps it's time. I checked for spark yesterday and it was a bit hard to see in the light outside, but it appears to be fine to me.

I did not mention previously that I just replaced the belts (you bet - eat your hearts out boys, my tiller has reverse) and I was forced to buy a thicker belt for the reverse than was previously mounted on my tiller. My favourite mechanic (son in law Noah) and I spent a few minutes on it yesterday afternoon. With Noah's finger on the throttle and my hand on the shifter, we found that when I slowly engaged the tines the governor really fought his finger to kill the engine. This lead us to remove the forward belt and that seemed to solve the problem. She walked backwards for about ten feet without any loss of power. It seems therefore that the belts are fighting each other when a gear is engaged, and the new, thicker reverse belt in combo with the new forward belt is too much for the engine. I think I'm saying this right - I'm a bit over my head again here. Unfortunately we didn't get any further because the girls found us in our Sunday clothes with the tiller apart and tools all around us. That was that!

So, I hope I've isolated the problem and will try to get to it tonight. I saved the old reverse belt and will remount it to see if if that solves it. I know I've got some engine work to do too, but want to try to get through the summer without pulling the whole thing apart. Doesn't help that there is no small engine shop in my town any more. I'm the type to pull it apart and then go parts shopping. Not the best practice I admit, but that's the way I've always done it.

Thanks again everyone for your helpful suggestions.
Tim

This could be tine bearings worn putting motor under to much pressure while trying to dig

1975 or so!! Check the compression and valve clearances and load/work wear.

Is ewalk still with us? I have not seen a post from him in a while.

mine is doing the same thing and it's real old , any conclusion that you came too pandoratim ??

worked fine last year

Please post a link to your Carb’s diagram of parts. I’ll be looking for a rubber seat that swells and needle and rubber seat starves the hot engine of fuel (when the engine gets hot)… Post a Pic of your carb to verify a bowl or diaphragm “at least”.

It can be anything from dirty carb or air cleaner to faulty spark plug to weak coil ., even timing or valve lash . On this is equipment you have to verify all above are up to spec !

Good Point! I just wanted to add to the list and suggest simplest first. Good Luck.

I have had my share of the “Power Fun”. I need to replace my 70s stee Leak Rake. LOL!

Nah Tom , Still Original Evil Bro from the Great White North ! How's that Drill Press holding up ? Getting some usage ? lol.

Yep, makes a great hanger!

Bahaha !