Carb jet?


I bought an old Powermate 3KW generator with a Tecumseh OHH55 5.5HP
engine that doesn't run as smoothly as I'd like, to me it sounds,
smells and the plug looks lean. The Date of Manufacture is 8068 which
appears to mean the 68th day of 1998, before gas contained 10%
ethanol. The carb looks like a Series 8, with no idle screw. The fixed
main jet is stamped 166.
Has anyone modified one of these to run better on modern gas? On other
old engines I back out the idle mixture screw, but this one doesn't
have one.
tia
jsw
Reply to
Jim Wilkins
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Could try a larger main jet? Or find a carb with an adjustable jet. Generally it's the newer crap that is not adjustable (for emissions control reasons)
Reply to
clare
I've worked on a couple Tec engines, with simple float carbs. The metering is performed through the bolt that holds the float bowl on. If you pull that bolt out, there is a small hole in the side, that comes up through the center of the bolt. Enlarging this hole will rich the mixture.
Before I did that (not reversible action) I'd want to try fresh gas of good brand, air cleaner, new spark plug, take the float bowl off and see if there's water, check the gap from the flywheel to the coil, and all that good stuff.
Reply to
Stormin Mormon
At work we have a Sears mower, about 5 years old. It has a Tecumseh engine. On first attempt at using this Spring, it started backfiring through the carb and will nearly break your arm when it pulls the start handle out of your hand.
We found the flywheel key broken and replaced it with the correct Sears Part Number. It still does the same thing, though not quite as bad.
Magnet to coil clearance is .003. Compression seems good.
Anybody have any ideas? (Well, other than changing the mechanism under the nameplate or the nameplate above the mechanism, or both)
Reply to
John Husvar
John Husvar fired this volley in news:jhusvar- snipped-for-privacy@news.eternal-september.org:
I'll venture a left-field guess.
I restored a Cushman motor scooter that had the same problem. The ultimate problem was points timing. They were way too open (worn), so they opened early enough to advance the timing too far.
But the intermediate problem was that every time I put a new key in the flywheel, it immediately "half-sheared" it (before it fully sheared it), so that the flywheel timing was off, too. That exacerbated the problem.
I guess if yours has fully-electronic ignition, this might not be the problem.
LLoyd
Reply to
Lloyd E. Sponenburgh
There is also a replacement available for that bolt that has an adjustable needle valve in it.
Reply to
clare
Sometimes being too lean on start will cause the kick-back too. And the kickback CAN shear the timing key. Using a bit of medium lock-tite on the crank taper can prevent the key from shearing too!!!
Reply to
clare
Thanks. That bolt with 166 stamped on it is the main jet. I was hoping there might be an ethanol replacement with a larger fixed orifice. No luck so far searching on the net.
jsw
Reply to
Jim Wilkins
Uh ... the key is SUPPOSED to shear. Like when the mower hits a rock. That's why they're made with aluminum. At least it's so for B&S engines.
Bob
Reply to
Bob Engelhardt
Sure. And then when you run over a rock or survey stake, the machine will bend the crankshaft instead of shearing the flywheel key. F'ing brilliant, you think?
Hint for Clare only: Some devices have a reason for existance.
Reply to
Stormin Mormon
The shear pin on the TOP of the engine gives minimal protection to the shaft on the BOTTOM of the engine. By shearing at the flywheel end it shuts the engine off immediately upon hitting something - limiting the amount of damage it will do to the crank - but certainly not eliminating damage.
And did you also know that trying to start the average vertical shaft lawn mower engine without a blade attached CAN shear the flywheel key?? This is because the "flywheel" on most current vertical shaft engines designed for direct blade attachment is way too light to allow the engine to run without the blade and the torsional reversals are strong enough to shear the key. The BLADE is the actual "flywheel" that provides the required inertia on these engines. Older engines with cast iron flywheels and horizontal shaft engines do not have this issue.
Reply to
clare
[snip]
I think that's right. Except the crank is already garbage & shutting off is probably to prevent collateral damage. And to keep the operator's underwear clean .
Bob
Reply to
Bob Engelhardt
The small engine shop gave me a used, larger 163 jet to try. (should prefix it "Me-") It passes an 0.036" drill bit which the 166 doesn't. So far the engine runs smoother but the plug still reads lean.
Wouldn't you expect a universal problem like this to have a simple, well-publicized solution? I've had to retune all my small engines for gas with ethanol.
jsw
Reply to
Jim Wilkins

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