# Bought a Treysit Sirometer



## ChrisJ (Nov 27, 2014)

After reading everything on here, and not being sure if my HMSK80 is set as high as it can be I finally decided to buy a tach.

The Treysit Sirometer seems to be liked by many, very affordable and very accurate. Not to mention, it has the same cool factor my Slacktube Manometer has, at least to me.

The last time I used the blower I noticed with the speed set a little higher it seemed much happier. It moved snow with more authority so I want to see where I'm actually set which is slower than that. I just didn't trust it so I backed off a little.

I'm betting I'm around 3000-3200 right now and it'll be nice to get a little more out of it.


Off topic :
For those that have never seen a slacktube I've attached some pictures. For some reason this simple device fascinates me. I used it for adjusting the manifold pressure on my boiler. It's dead accurate by nature and always will be.

Please, leave working on gas appliances up to the professionals.


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## Geno (Nov 29, 2011)

*manometer..*

Not sure- But I had something like that once to synchronize the 4 carbs on a 1200 v-max motorcycle motor (mounted on a snowmobile of course)- It worked great.. but can't recall 'how' it worked anymore. It dialed in the carbs near perfect. Think something to do with flow of ventures or vacuum? Just know it had the same shape and had to get the two sides level I believe. sound right?


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## micah68kj (Oct 8, 2011)

I used to fool around with MG's back in the day. They had twin SU carbs and seemed to me I had some kind of balance meter that had fluid in it. If I recall correctly it was placed over the venturi and you had to get them to read the same. Man has that been a lifetime ago.


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## Geno (Nov 29, 2011)

I hear ya Joe.. I think it was 1986 or 87 on mine. I do remember the 'balance' you mentioned. a must for multiple carbs. Sounds like you had a very cool car! Don't we wish we had kept them from the day.


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## motorhead64 (Dec 15, 2013)

The Treysit Sirometer, also known as the "vibratach," is a great tool for any mechanic's toolbox. No outlets needed, no batteries, and very accurate. Used to be around $20...more now, I,m sure. I have one in my truck at all times. I have had the same two for years and they still work like a charm. When you first use one, you will smile. The guy who invented it should have been knighted! MH


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## micah68kj (Oct 8, 2011)

Geno said:


> I hear ya Joe.. I think it was 1986 or 87 on mine. I do remember the 'balance' you mentioned. a must for multiple carbs. Sounds like you had a very cool car! Don't we wish we had kept them from the day.


I had at least a half dozen of those dang cars. I loved them. I called them the poor man's Jag. So much fun to drive and really a very simple straightforward car. I bought my last one around '88. Lost interest in it and let it go. Most of mine were from the 60's and early 70's.


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## CarlB (Jan 2, 2011)

If you have a multi meter with that can measure frequency you can use it to measure the rpm. Hz measurement x 60 = RPM

50hz = 3,000 55hz =3300 60hz = 3600rpm etc.

Take the positive probe and just lay it on the spark plug wire. If a clip on type just clip it over the spark plug wire.

How To - Measure RPM's with a Multimeter - Electrical - RedSquare Wheel Horse Forum


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## ChrisJ (Nov 27, 2014)

CarlB said:


> If you have a multi meter with that can measure frequency you can use it to measure the rpm. Hz measurement x 60 = RPM
> 
> 50hz = 3,000 55hz =3300 60hz = 3600rpm etc.
> 
> ...



I do,
However I don't think I feel comfortable doing this with my Fluke 179 which is the only meter I have with a frequency counter. Last time I looked these were selling for $300 so damaging it would really suck.


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## ChrisJ (Nov 27, 2014)

Curious what RPM everyone recommends setting the Tec HMSK80 to? I know it's spec'd to run at 3600 so I was planning on aiming for that.


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## whimsey (Oct 16, 2014)

micah68kj said:


> I had at least a half dozen of those dang cars. I loved them. I called them the poor man's Jag. So much fun to drive and really a very simple straightforward car. I bought my last one around '88. Lost interest in it and let it go. Most of mine were from the 60's and early 70's.


In 1970 my friend had a late 60's Austin Healy Sprite, the same car as the MG Midget at that time. It was a blast to drive and ride in. Doing 55 felt like you were doing a heck of a lot faster. Your butt was inches from the ground. Sad to say it caught fire while waiting in line at a NJ motor vehicle inspection station .

Whimsey


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## classiccat (Mar 1, 2014)

ChrisJ said:


> Curious what RPM everyone recommends setting the Tec HMSK80 to? I know it's spec'd to run at 3600 so I was planning on aiming for that.


Hey Chris! I always shoot for 3500 when the engine is at operating temperature. It will run lower RPM when cold. 

I use a sirometer when an inductive tach isn't already installed; all of my tecumseh's have permanently-mounted Hardline tach/hour meters...really nice for monitoring not only high RPM but how my machines behave under various load conditions.


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## ChrisJ (Nov 27, 2014)

classiccat said:


> Hey Chris! I always shoot for 3500 when the engine is at operating temperature. It will run lower RPM when cold.
> 
> I use a sirometer when an inductive tach isn't already installed; all of my tecumseh's have permanently-mounted Hardline tach/hour meters...really nice for monitoring not only high RPM but how my machines behave under various load conditions.



What do you typically see these Tecumsehs do under load? How much does the RPM drop? For example if your unloaded rpm is 3500 what does it drop to when really put under a load?



I was thinking of aiming for 3500ish as well to be on the safe side.


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## classiccat (Mar 1, 2014)

ChrisJ said:


> What do you typically see these Tecumsehs do under load? How much does the RPM drop? For example if your unloaded rpm is 3500 what does it drop to when really put under a load?
> 
> 
> 
> I was thinking of aiming for 3500ish as well to be on the safe side.


Good plan! 

I only have ~11hrs on my '89 Toro 824 but so far (_going off of memory_), 3100 is the lowest I remember seeing the HM80 chug-at on slushy EOD before the governor settles-in. Normal EOD was 3200-3300. 3300-3400 would be full bucket for a normal consistency snow. 1/2-bucket or less it barely comes off of 3500 if at all. Thinking about it, a go-pro would be neat for recording this! 

Keep in mind that this machine is tricky for gauging engine load since the drum auger makes it difficult to overfeed the impeller..._despite the fact that on the lowest speed it's traveling ~ 4fps...like trying to walk a bull on a leash _


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## ChrisJ (Nov 27, 2014)

classiccat said:


> Good plan!
> 
> I only have ~11hrs on my '89 Toro 824 but so far (_going off of memory_), 3100 is the lowest I remember seeing the HM80 chug-at on slushy EOD before the governor settles-in. Normal EOD was 3200-3300. 3300-3400 would be full bucket for a normal consistency snow. 1/2-bucket or less it barely comes off of 3500 if at all. Thinking about it, a go-pro would be neat for recording this!
> 
> Keep in mind that this machine is tricky for gauging engine load since the drum auger makes it difficult to overfeed the impeller..._despite the fact that on the lowest speed it's traveling ~ 4fps...like trying to walk a bull on a leash _


Have you ever observed what the carb is actually doing during this?
When I was adjusting mine Saturday I went into some deep now filling the bucket and it seemed like the carb never opened more than maybe half way.

RPMs still seemed good so I have to assume it was working good. Just seemed odd because if that doesn't do it, what will.


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## classiccat (Mar 1, 2014)

ChrisJ said:


> Have you ever observed what the carb is actually doing during this?
> When I was adjusting mine Saturday I went into some deep now filling the bucket and it seemed like the carb never opened more than maybe half way.
> 
> RPMs still seemed good so I have to assume it was working good. Just seemed odd because if that doesn't do it, what will.


I'm afraid not...always have the heatbox installed when blowing snow.

I can tell you that at high-speed / no-load, the butterfly should be barely off of the idle speed screw.

hmmm...now we need 2 go-pro cameras...one on the tach & the other on the carb


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## RedOctobyr (Mar 2, 2014)

ChrisJ said:


> Have you ever observed what the carb is actually doing during this?
> When I was adjusting mine Saturday I went into some deep now filling the bucket and it seemed like the carb never opened more than maybe half way.
> 
> RPMs still seemed good so I have to assume it was working good. Just seemed odd because if that doesn't do it, what will.


I'd set my HMSK80 to 3600. I never watched it during a heavy load. 

But last week I started looking into this on my current OHSK100, observing how far the governor opened the throttle under the heaviest load I could provide. I made a thread about it: 

Tecumseh OHSK100 governor linkage setup, governor sag

I run the engine at 3600. Last week I saw the tach show 3150 at one point, under a big load. 

I just replaced the governor spring yesterday. Afterwards I tried to repeat the test. While driving it into a full bucket of the same snow, this time I noticed 3450. 

Now, this is not scientific. I didn't have a camera going, so I can only judge by what I happened to observe on the tach, while also managing the machine. I can't guarantee I saw the lowest numbers. But I'd say that the RPM didn't seem to drop as far, after the new governor spring and re-adjusting the governor linkage. 

I wish I could do a more controlled test. But perhaps what I observed is still useful. And I'd like to hear from other users too. I'd like to see the throttle open fully before the RPM sags. I'm not getting that, but at least it may be a little better now. 

But in a few sessions of heavy-load testing, I've never seen the throttle open fully, other than when I snap the throttle lever from idle to full. So either the 10hp engine is super-powerful relative to the 24" bucket, or the governor still isn't as "insistent" as I'd like.


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## ChrisJ (Nov 27, 2014)

RedOctobyr said:


> I'd set my HMSK80 to 3600. I never watched it during a heavy load.
> 
> But last week I started looking into this on my current OHSK100, observing how far the governor opened the throttle under the heaviest load I could provide. I made a thread about it:
> 
> ...



It seems to me like the governor on the Tecumseh isn't near as responsive as the one on my 8 HP Coleman generator. That thing throws a fit if the engine slows up even the slightest amount.


I don't really have much more I can change other than the governor it self. New throttle, new linkages, new OEM carb.


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## classiccat (Mar 1, 2014)

ChrisJ said:


> It seems to me like the governor on the Tecumseh isn't near as responsive as the one on my 8 HP Coleman generator. That thing throws a fit if the engine slows up even the slightest amount.
> 
> 
> I don't really have much more I can change other than the governor it self. New throttle, new linkages, new OEM carb.


Hey Chris, Have you tried resetting / synchronizing the governor arm with the carb butterfly?


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## ChrisJ (Nov 27, 2014)

classiccat said:


> Hey Chris, Have you tried resetting / synchronizing the governor arm with the carb butterfly?


Yep,
When I got this blower the arm wasn't even on the governor anymore. Basically I set it up so the carb can open fully and close fully. I may have tweaked it after that to get it running the right RPM vs the throttle control. You know, so the screw on the control isn't all the way out, or all the way in but somewhere in the middle etc.

With the engine off the carb is wide open with a fair amount of spring tension against it when the throttle is all the way up.


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## RedOctobyr (Mar 2, 2014)

ChrisJ said:


> It seems to me like the governor on the Tecumseh isn't near as responsive as the one on my 8 HP Coleman generator. That thing throws a fit if the engine slows up even the slightest amount.
> 
> 
> I don't really have much more I can change other than the governor it self. New throttle, new linkages, new OEM carb.


Does yours have a visible spring involved between the linkage driven by the throttle lever (moved by the operator), and the throttle plate (the actual throttle on the carb)? I just replaced that spring on mine, which seems to have helped. (the pics in my thread show this spring) 

For other options, I don't know. I haven't experimented further yet. I've wondered what would happen if: 

- I used a stiffer/shorter spring, even when compared to the new replacement, which is shorter than the old one I removed. Or if I did something like doubling-up on the spring. 
- I extended the governor's arm slightly, and attached the throttle-plate linkage there. 

I fear I'd just make things worse. When I made a change to the linkage setup of the governor last week, I apparently introduced some surging. So I presumably upset the delicate balance of the system. But I *would* like to make it hold RPM as firmly" as possible. 

Now, my Generac generator's service manual tells you to set the gov for 62-63 Hz with no load, as I recall. Then, as a load is added, it drops to around 60 Hz. So even a generator governor has some sag. But if I could make this one more aggressive with the throttle, that would be nice. 

This has gotten me wondering about the Predator engines, etc, that are more powerful with less displacement. I wonder how much of that might be related to governors that simply work better. When my engine was slowing down, I'd assumed I was simply out of power. But that wasn't true, the throttle still wasn't open all the way. The governor was making the engine seem weaker than it really is.


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## ChrisJ (Nov 27, 2014)

RedOctobyr said:


> Does yours have a visible spring involved between the linkage driven by the throttle lever (moved by the operator), and the throttle plate (the actual throttle on the carb)? I just replaced that spring on mine, which seems to have helped. (the pics in my thread show this spring)
> 
> For other options, I don't know. I haven't experimented further yet. I've wondered what would happen if:
> 
> ...



No, the only spring is a coil type one in the throttle control and that came new with the new control.

The Predator engines are more powerful because they are overhead valve designs more than anything else.

I've also felt the governor on Honda engines seems more responsive than the Tecumseh, but I could be wrong.


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## ChrisJ (Nov 27, 2014)

Checked my rpm today. I had it set to 3000 so decided to up it to approx 3500.

Holy cow is there a huge difference. It's like a completely different machine! Now it really runs strong and throws snow with authority! The governor seems much more responsive as well which makes me happy.

I guess that's what happens when something isn't set to what it's designed for.


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## ChrisJ (Nov 27, 2014)

Thought I added a video to this.

Here's a video of it running @ 3500 rpm. Has a little hiccup near the end of the video because I was running it out of gas.


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