Tecumseh RPM Range - What's Normal? - Snowblower Forum : Snow Blower Forums
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post #1 of 20 Old 03-13-2017, 06:50 PM Thread Starter
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Tecumseh RPM Range - What's Normal?

I just tried out my new Briggs + Stratton vibration tachometer, and it's great!
Used it on a '94 Tecumseh flathead Snowking engine. Here's what I got.

Idle 2,200 rpm

High 3,900 rpm

How are those numbers? Does my machine need adjustment?


Here's a pic of the sirometer (vibration tachometer)

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post #2 of 20 Old 03-13-2017, 06:57 PM
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If that's accurate you may want to slow it down, Tecumseh has a great engine but they don't like much above 3600, There known to break the piston shaft and ventilate the case when it happens.

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post #3 of 20 Old 03-13-2017, 06:57 PM
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3900 is way too high. a tecumseh should never exceed 3600. That idle is about right.

This happens when tecs run low on oil &/or are over-revved (broken connecting rod):


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Last edited by classiccat; 03-13-2017 at 06:59 PM.
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post #4 of 20 Old 03-13-2017, 07:17 PM
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I dunno, I think some Seafoam ought to fix up that blown connecting rod

Yeah, take it down to 3600, or whatever the manual says. The manual may also have a suggested idle RPM. I believe the idle speed is selected to keep it from stalling, but also to provide enough circulation of the oil.

How is the vibratach to use? I was thinking about getting one, but ended up buying a tachometer/hour meter instead.

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post #5 of 20 Old 03-13-2017, 07:51 PM Thread Starter
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3,900 is too high? Ok, good to know.
Idle of 2,200 sounded high to me. But if you guys say that's normal, then I'm ok with it.
A working range of 2,200 to 3,600 isn't much.

The vibratach is used by holding the unit firmly against the machine, and then turning the dial. Turning the dial feeds the wire in/out, and when the engine vibration matches the harmonic frequency of the wire length, the end of the wire vibrates at it's maximum. You then read the dial.
It sounds hard, but in actual use it's amazingly simple and easy.

I thought about mounting magnets to the bottom of the unit, to free one hand, but I think the engine shakes too hard for this.
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post #6 of 20 Old 03-13-2017, 07:56 PM
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I recently bought one of those vibratachs. Really, really cool tool. Surprisingly easy to use

My machine:
1979 Ariens 924039 (24", 8hp w/ differential)
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post #7 of 20 Old 03-13-2017, 07:59 PM Thread Starter
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Originally Posted by Stang View Post
I recently bought one of those vibratachs. Really, really cool tool. Surprisingly easy to use
Hey, the vibratech (and this forum) stopped me from over-revving my engine.
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post #8 of 20 Old 03-13-2017, 09:16 PM
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I was shown the VibraTach by a John Deere dealer in 1979. He loved it and used it all the time.

I'd like to see someone compare that using a light tach to see how accurate it is. If it's off 100 rpms at 3,600 that could be a devastating difference to a Tecumseh engine.

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post #9 of 20 Old 03-13-2017, 09:40 PM
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not saying the sirometer is inaccurate..but you cold just use a digital single wire tach that wraps around a spark plug lead. simple to use permanently or just temporary for testing. they are about 12 dollars from many places including ebay..

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post #10 of 20 Old 03-13-2017, 10:03 PM
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Quote:
Originally Posted by Sign216 View Post
I just tried out my new Briggs + Stratton vibration tachometer, and it's great!
Used it on a '94 Tecumseh flathead Snowking engine. Here's what I got.

Idle 2,200 rpm

High 3,900 rpm

How are those numbers? Does my machine need adjustment?


Here's a pic of the sirometer (vibration tachometer)

.


How long have you been runnng it @ 3900 ? years?
if so maybe they throw rods from bad maintenance/ low oil not being run above 3600 +/- 150
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