1999-2000 Tecumseh OHV 17.5hp in Huskee 42” Tractor Supply Mower

[Sears L2000]

New plug, oil, oil filter, air filter, fuel filter, shut off, flushed fuel line segments, valve lash was 0.012-0.013”, never before apart or adjusted, set to 0.004”, spark pickup correct at 0.12X”, new fuel, engine shell off, nearly clean and cleaned to aluminum.

Has a spark pickup tach attached. Max at 3200 unless pull the governor arm. If at idle after adjusting, starts at 1700 and drifts to1300-1400 and sometimes lower to stall. Carb has an idle screw adjustment and the throttle lever has an idle or low end setting. De-conflicted them so bottom throttle opening of each is the same.

BEFORE: When running dull throttle, it formerly ran normal, but after minute or two drifted down, down, down to stall. Never quite knew what was next. (Fuel float inlet seat was gas destroyed. Closed off needle valve hole almost completely. Fuel starvation.)

NOW: Replaced bottom half of Tecumseh carb #640065 with a new bottom half. These are the plastic bowl ones with metal bail wire holding on. Fixed high speed tube air mixer? and fixed idle jet separate.

Essentially the same. If runs to hot, seems to run. Not smoothly. Giving it a little choke keeps it running or running longer.

Does not restart well. Usually needs choke and full throttle. Cranks and makes smoke on start.

Mower deck pulls it down to 3100+/-.

When put to idle drifts from 1600+/- down to 1200 or less to usually stall.

The RPM is erratic enough its confusing.

CHOICE seems to be rebuild old bottom with a new float inlet seat, OR, borrow the high speed jet from the old one and put it in the new bottom.

GUESS: My guess is the high speed jet in the new bottom is too small. Trading jets might fix it.

It runs fairly smooth at 3000, but not at 3200. You can hear the misses.

Shame. Shell looks new and the hydro trans works perfectly. Little to no wear or rust.

 

[Tiger Small Engine]

New plug, oil, oil filter, air filter, fuel filter, shut off, flushed fuel line segments, valve lash was 0.012-0.013”, never before apart or adjusted, set to 0.004”, spark pickup correct at 0.12X”, new fuel, engine shell off, nearly clean and cleaned to aluminum.

Has a spark pickup tach attached. Max at 3200 unless pull the governor arm. If at idle after adjusting, starts at 1700 and drifts to1300-1400 and sometimes lower to stall. Carb has an idle screw adjustment and the throttle lever has an idle or low end setting. De-conflicted them so bottom throttle opening of each is the same.

BEFORE: When running dull throttle, it formerly ran normal, but after minute or two drifted down, down, down to stall. Never quite knew what was next. (Fuel float inlet seat was gas destroyed. Closed off needle valve hole almost completely. Fuel starvation.)

NOW: Replaced bottom half of Tecumseh carb #640065 with a new bottom half. These are the plastic bowl ones with metal bail wire holding on. Fixed high speed tube air mixer? and fixed idle jet separate.

Essentially the same. If runs to hot, seems to run. Not smoothly. Giving it a little choke keeps it running or running longer.

Does not restart well. Usually needs choke and full throttle. Cranks and makes smoke on start.

Mower deck pulls it down to 3100+/-.

When put to idle drifts from 1600+/- down to 1200 or less to usually stall.

The RPM is erratic enough its confusing.

CHOICE seems to be rebuild old bottom with a new float inlet seat, OR, borrow the high speed jet from the old one and put it in the new bottom.

GUESS: My guess is the high speed jet in the new bottom is too small. Trading jets might fix it.

It runs fairly smooth at 3000, but not at 3200. You can hear the misses.

Shame. Shell looks new and the hydro trans works perfectly. Little to no wear or rust.

If you can set the idle at 1850 RPMs, and it won’t maintain idle, then there is most likely a problem with pilot jet. If you have gone through the carburetor thoroughly, cleaned it, and set idle, that is all you can do. Some carburetors just don’t come back and run right after servicing them. Don’t be afraid to buy an aftermarket carburetor for cheap and install it. I have had solid results over the years with the right aftermarket carburetor. Order the carburetor based on the model number of the engine, compare pictures, measurements, reviews, and go for it.

 

[Sears L2000]

I took the HS fuel orifice out of the old bottom which had a gas wrecked inlet seal. Substituted the old orifice in the new bottom. Some ceramic thing versus metal. Seemed to start easy, shut off and restart normally, not needing choke to restart, and run at full speed smoothly. Not audible wobble. Rain started before under load mowing load test.

Perhaps solved. Now I have a hybrid set in the mower and needles and seats to fix the old bottom if needed.

Some research says the Tecumseh 17.5hp engines operate at a maximum of 2800-3200 rpm unless in a generator where 3600 is required.

So the governed speed is not an issue working in the 3100-3200 range. Load-no load.

Setting the idle is next. The Tech manual says the carb screw should be set at a minimum 600 rpm under the governor low end screw. So I Guess you back off the governor screw, set the carb screw, and turn the governor screw back in for faster.

Then I have to HeliCoil one of the four engine mount bolts some DSOAB put a 10mm bolt into a 3/8” hole and stripped the threads. Not me.

 

[Auto Doc's]

It would help greatly if you could give us the engine product label information but is likely gone or very worn down at this age.

Don't mix new aftermarket carburetor parts with the original. Fix the original carburetor if at all possible. There are several You Tube videos that go over these carburetors in great detail. It does take some searching though.

James Condon has some great videos that go over this carburetor design very well. Raley's small engine is another good source online for videos. These carburetors were specific to the Tecumseh engine equipped products.

The trouble with aftermarket carburetors is that they are not calibrated to run you engine correctly and they are "universal fit", not OE.