Tecumseh RPM Specs?

[oldstuff]

Hi everyone,

First of all, could someone please tell me the recommended rpm range for Tecumseh TVS90-43572K(Sears 143.943508-4168J)?

Secondly, my Tecumseh manuals point to microfiche card #30, or consult service bulletin #107, neither of which seem to be available on the Web. What about RPM specs for other Tecumseh engines I'm sure to come across in the future?

Finally, assuming safe engine operating speeds are a good thing...why are these Tecumseh specs so hard to come by?

-Chuck (overly geeked from purchase of an electronic RPM tester bought to improve the quality of my tune-ups. )

[T-Man]

Overly Geeked Chuck,

Not to worry....WE LIKE GEEKS...when it comes to wanted to do things right.
For a long time, Tecumseh RPM specs have not been readily available. I always
used fiche card #30, back in the "good ole days" when those dinosaurs were still
being produced. To add to this problem....Tecumseh is NO LONGER IN BUSINESS
as an engine builder, so NO spec info has been produced for a while. Used to be,
when you looked up a replacement shortblock or engine.....it would give you the
high and low, OR....the high ONLY (when no idle is used on the spec)...TOP and
IDLE RPM's specs for each model spec. Now...even that is somewhat of a mystery. I don't
know this answer currently....What is parts look-up now? Still PartsManagerPro....or an ARI based
look-up now? Is there a charge for parts look-up now? Does CPC offer such?

Can U tell....I've been "out of the loop" for a while ??

T-Man (Ice/Snow Comes to Dixie !!)

[nevadawalrus]

The TVS-90 typically is a rotary mower engine which means its rpm is regulated by blade tip speed rather then the engine ultimate capability. 21' BLADES are around 3200 rpm, 22" will be a bit alower and 20" a bit faster. Blade tip speeds are a government safety standard.

As for idle speeds, depends if the engine is pre emission or not. Pre emission carbs will idle down a little slower, areound 1800 rpm while emission engines built in the last 10 or so years will be higher, more like 2200 rpm.

[oldstuff]

Hey T-Man, hey Bob,

I did find some blade tip speed formulas I could use since indeed, as nevadawalrus alluded, this engine's on a lawn mower.

Caution! The following is for informational purposes only - it is not in any way to be used or construed as being a recommendation of any kind. It has not been checked or verified as being accurate or safe in any way. Always seek the advise of a certified licensed mechanic!

To calculate blade tip speed, multiply the length of the blade times engine RPMs and multiply the result times pi (3.14), divide this by 12 and the product is the blade tip speed in feet per minute.

Blade length X RPM's X 3.14 / 12 = Blade Tip Speed in Feet Per Minute.

If maximum blade tip speed per government standards is 19,000 feet per minute, then maximum RPM's based on blade size can be calculated:

19000 divided by [(Blade length X 3.14) divided by 12)] = Max RPM's

My engine's on a 20" lawn mower, so:
20 X 3.14 = 62.8 divided by 12 = 5.233,
19000 divided by 5.233 = 3630 max rpm.

20" mower, below/under 3600 max RPM.

21" mower, below/under 3450 max RPM.

22" mower, below/under 3298 max RPM.

Addendum:
Subtract 200 RPM's to compensate for governor lag time:

20" mower under 3400 max RPM
21" mower under 3250 max RPM
22" mower under 3100 max rpm

(Thanks to nevadawalrus)

Please let me know if all or any of this is in error!

I am not responsible or in any way liable for any use or misuse of the above information, nor any deaths or injuries that may lead to or result from any application of it. Always seek the advise of a certified licensed mechanic!

-Chuck

[nevadawalrus]

Those numbers sound right. The full government recomendation suggests setting approx 200 rpm below to compensate for governor lag time, so for simple rounding off I adapted 3200 rpm when these specs first became law. If you were to check rpm on a brand new mower the factorys generally have them set even lower. The shop I worked for sold Toro, Honda and Snapper mowers and every one of them was a good 50 to 100 rpm slower then the 3200 I adapted as my standard on 21" decks so when servicing a new sale I was always cranking them up from the factory setting. Honda's I would go to 3300 rpm because the quality of their governor system meant there was less lag time when passing from a heavy cut to concrete, they won't rev up as much as other engines before the governor caught it and brought it back down.

Back in the early 80's when the safety regs came into effect, most of us only had vibra tachs and rounding down to make sure we didn't violate safety standards this round down made sense to me. Today most shops use electric tachs which make more precise settings easy but even with the electric tach I never changed from my old habits. I saw no logic in cahnging my habits when the factory settings were so slow.

[oldstuff]

Best to stay at least 200 RPM's below maximum, then.
Will do...thanks for that Bob!

...If you were to check rpm on a brand new mower the factorys generally have them set even lower. The shop I worked for sold Toro, Honda and Snapper mowers and every one of them was a good 50 to 100 rpm slower then the 3200 I adapted as my standard on 21" decks...

And the customer thinks, "Gee, these new ones run so smooth and quiet!"
He reaches for his wallet.

-Chuck

[bobodu]

As long as the people who pay me don't have "an electronic RPM tester bought to improve the quality of my tune-ups" .... I ain't gonna lose any sleep.

[OldLawnMowerMan]

If I really wanted to know the RPM of my mower, I am out of luck until I find a Tecumseh service manual binder on eBay containing service bulletin #107 and microfiche card #30.

Could you please, in the meantime, give me the microfiche-specific speed ratings for these following engines?
TNT100-10056
TNT100-10061
TNT100-10083
TNT100-10095
TNT120-12000
TNT120-12004
TNT120-12005
TNT120-12009
TNT120-12010
TNT120-12011
TNT120-12012
TVS90-43388F
143.234062 (ECV100-145035A)
143.234072 (ECV100-145036A)
143.234082 (ECV100-145037A)
143.234092 (ECV100-145038A)
143.235012 (ECV120-152005)
143.235022 (ECV120-152006)
143.286142 (VM80-150119E)
143.996704 (VLV126-502525D)

Thank you,



Ben Edge (OldLawnMowerMan)

[OldLawnMowerMan]

Those numbers sound right. The full government recomendation suggests setting approx 200 rpm below to compensate for governor lag time, so for simple rounding off I adapted 3200 rpm when these specs first became law. If you were to check rpm on a brand new mower the factories generally have them set even lower. The shop I worked for sold Toro, Honda and Snapper mowers, and every one of them was a good 50 to 100 rpm slower than the 3200 I adapted as my standard on 21" decks, so when servicing a new sale, I was always cranking them up from the factory setting. Honda's I would go to 3300 rpm because the quality of their governor system meant there was less lag time when passing from a heavy cut to concrete, they won't rev up as much as other engines before the governor caught it and brought it back down.

Back in the early 80's when the safety regs came into effect, most of us only had vibra tachs and rounding down to make sure we didn't violate safety standards this round down made sense to me. Today most shops use electric tachs which make more precise settings easy but even with the electric tach I never changed from my old habits. I saw no logic in changing my habits when the factory settings were so slow.

So, that would mean that if Toro had specified 3000 RPM maximum for a lot of its supplied lawnmower engines, you'd really be setting those up to 2800 RPM max to account for governor lag time?

[nevadawalrus]

No need to since you would be well under 200 rpm below Government safety specs to begin with.