1969 Sears Suburban 12 "Putt Putt'

You have to keep in mind that it's a flathead and like all flatheads there's a chance the valve clearances tighten up which requires removing and grinding/polishing the tips to get proper clearance back. Anytime you have ANY small engine with low compression, poor running no matter what you do and it backfiring first check and adjust the valve clearances whether it be a flathead or a OHV. I've brought many rough running engines back to life by doing so.

Brianator wrote:

You have to keep in mind that it's a flathead and like all flatheads there's a chance the valve clearances tighten up which requires removing and grinding/polishing the tips to get proper clearance back. Anytime you have ANY small engine with low compression, poor running no matter what you do and it backfiring first check and adjust the valve clearances whether it be a flathead or a OHV. I've brought many rough running engines back to life by doing so.

Set it to factory clearance when I built it.

@Slipperz I can't get anything to run on it. It's an HM100. I'm debating on trying to fab an adapter for a Honda clone carb, or Tillotson fuel injection.

@Ifitaintbroke
I have been really interested in that Tilly fuel injection as of late so that would be sweet to see and its not much more that a normal carb!
Though at this point I doubt you have a carb problem, seeing you seem to have tried multiple and I assume their were either freshly rebuild or new?
Did you not polish and port that head? Would that mess with clearances? (SpitBallin here as I have never modified a head before.)

Slipperz wrote:

@Ifitaintbroke
I have been really interested in that Tilly fuel injection as of late so that would be sweet to see and its not much more that a normal carb!
Though at this point I doubt you have a carb problem, seeing you seem to have tried multiple and I assume their were either freshly rebuild or new?
Did you not polish and port that head? Would that mess with clearances? (SpitBallin here as I have never modified a head before.)

It is definitely a carb problem. None of the carbs worked, but they all had different problems. The Tillotson FI is great. I have it on my Predator 212 on my tiller. It works pretty good. I'll get some pics sometime. Tillotson makes a larger version, which I may try on the Tescumbag. I need to pull the side cover off and tighten up the crank endplay (sound familiar?).

@Ifitaintbroke
I have never been inside my motor so I couldn't say on the crankshaft endplay. Also we do not have the same series of engines with mine being a HH series and your being a HM. I assume they would be similar since how different can a flathead engine be from another one but not sure. I know the HH Tecumseh's are know to be quite reliable little engine ONCE you tear the Tecumseh carb off of them and swap to something else I.E a Kohler carb. I am pretty sure most Tecumseh carbs have bad float and needle designs and if you hit a bump they are know to stick the needle. So perhaps you should try a new clone Kohler swap? You will though need to drill out the holes and modify the choke linkage as it was too long to fit with the tractor's airbox. Not sure though with you application. They are cheap carbs anyways so if it does not work you would not be out too much.

@Slipperz You can feel crank endplay externally and if you have a dial gauge you can measure it too, perhaps even with a set of feeler gauges? Just grab the pulley and push it in and out, there should be a little of play but not too much even 1/16" is borderline too much.

I have a 1974 HH100 and it's been rock solid aside from the compression getting really low, can't blame it after all these years. It's a utility tractor so not as much abuse as a ATT.

I also have a 1979 OH140 in the Roper Offroadster and found that the carb needle just floats in there and doesn't have a retaining clip like B&S engines so I actually modified one to fit because I thought the carb was causing the issues (surging bad and spitting black smoke every time it "hitched").

Turns out the throttle return spring was out of place, the high speed governor adjustment screw was out of whack AND the low speed governor screw was missing, took a while but once I had them dialed in my "carb issues" were solved! I've found that all older Tecumsehs are really dependent on having the governor correctly adjusted and the air/fuel screw as well even the Snow King snowblower engines are like that.

Don't be afraid to keep digging @ifitaintbroke I have and I've been rewarded 9 out of 10 times, there's always the possibility that a different carb masks the actual problem because it has the air/fuel and jetting setup different.

Well I went and did some logging!
Here is a video of some micro logging!

Next thing for this guy is probably belt keepers on the trans as we currently have none on it at all!