Briggs 126T02 - Hard Starting then Running Rich

[dougand3]

Briggs 126T02-0675-B2 08031563
Friend has this engine on mower and wants me to look at. Poor starting, won't re-start. I know very little about AutoChoke-Vane engines. I see it's running real rich with black exhaust smoke and black plug. With the little time I've had it running, I could push air vane away from flywheel (stretch spring effectively) and get it to run smooth. I've disassembled and cleaned carb - but it looked real clean inside beforehand. The needle seat looked ok but could be bad. I get consistent spark with an in-line tester. I could not get spark grounding plug on fins - puzzles me.I read that it has a thermostat inline with muffler....changes shape to alter air vane? What tends to fail on these... Air vane? Thermostat? Gov or air vane springs? What I should check next? Thanks, Doug

[bgsengine]

There's a bulletin out on them and a new thermostat design (593208 - have sold a ton of them this year) as well as an adjustment check to do with the t-stat - also check the blower housing and cooling fins for any blockage - reduced air flow obviously affects vane operation - the t-stat arm can rust in place if left to set out in the elements or sitting out for a long time without running.

[dougand3]

Thanks, bgsengine. Do you need to replace air vane, too?
Why did these autochoke engines come into being? Easier EPA pass? Cheaper to make? Less thought required to start?

[bgsengine]

Thanks, bgsengine. Do you need to replace air vane, too?

Only if it is broken

Why did these autochoke engines come into being? Easier EPA pass? Cheaper to make? Less thought required to start?

All of the above.

[dougand3]

Got new tsat on and adjusted. Mower ran fabulously for 5 mins....then abrupt stop, as in spark went bye bye. No re-start after multiple pulls and plug is wet. So, I'm thinking I need a coil. Then starting looking at safety assy that is defeated when you pull handle. It only moved 3/16" with pull handle depressed. I removed the HEAVY DUTY spring and then pull handle moved assy 1/2". Put a weaker spring on and it runs like a champ. So, safety assy was halfway defeated with strong spring - allowed crankshaft to turn but didn't allow spark. I think the cable has stretched some due to force necessary to overcome spring. Way more spring here than Briggs needs. I guess they are looking for an ABRUPT STOP for the morons who mow sideways on a 60* slope and flip it.

Briggs spring on L, (removed). Weaker spring on R.

[Mek-a-nik]

Got new tsat on and adjusted. Mower ran fabulously for 5 mins....then abrupt stop, as in spark went bye bye. No re-start after multiple pulls and plug is wet. So, I'm thinking I need a coil. Then starting looking at safety assy that is defeated when you pull handle. It only moved 3/16" with pull handle depressed. I removed the HEAVY DUTY spring and then pull handle moved assy 1/2". Put a weaker spring on and it runs like a champ. So, safety assy was halfway defeated with strong spring - allowed crankshaft to turn but didn't allow spark. I think the cable has stretched some due to force necessary to overcome spring. Way more spring here than Briggs needs. I guess they are looking for an ABRUPT STOP for the morons who mow sideways on a 60* slope and flip it.

Briggs spring on L, (removed). Weaker spring on R.

Usually, the cable seizes up from sitting outside.

[bgsengine]

Yeah also the cables do not stretch, really - more likely the housing melted or kinked , and the snap-in uppers tend to "keel over" after a while, also there are dozens of different cables some with only difference being a quarter inch in length so a "will-fit" cable may not be the right one - The stronger spring is the correct spring to have and by bypassing that with a weaker spring, if you were doing this as a professional shop, you'd be open to potentially millions of dollars in liability if someone got hurt using that mower because the blade brake did not stop the engine fast enough.

Which is why we are always very careful to get the exact fit correct cable for every mower that needs one, and fix them right.

"Close Enough" could cost you your business and livelihood.

I would advise to find a correct replacement cable (they are relatively cheap) for the specific model of mower and put the stronger spring back in where it should be.. any liability after that, the burden then also falls on the manufacturer that says that cable is the right one for that mower, and/or the engine maker (assuming the flywheel brake is serviced and adjusted correctly) - The standard is the blade stops within 3 seconds of releasing the bail handle.

Other than that, just be sure you understand the product liability risk you take by altering them in that way.. your mileage may vary - if you trust the mower owner to not come after you for faulty work, it's up to you.

[dougand3]

Thanks for the liability data. Not an issue here but can see a potential problem if a pro shop did it for a sue happy customer.