Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Horizontal lists don't usually post correctly so the info below.....

Make...............Engine RPM,,,,,,Auger dia........Auger RPM................Velocity out ft/min

Powerlite,  .........4000....................7........................1550..............................2840

Murray 3ph........4100..................8 1/4....................1025..............................2213

Maco 3hp...........4100..................8 1/4....................980...............................2116

Borat....................6000.................8 1/4...................1470.............................3173

Toro 350..............4200.................8 1/2.....................xxxxx..............................xxxxx

Borat,

    Your auger RPM was approximated from Maco's.  Different belts but likely both pulley diameters are the same or very close.  The estimate was 245 RPM per 1K engine RPM.

     It would be interesting to compare impeller bearings.   Murray and Maco both have roller bearings in the drive side of the auger shaft, flange on the other.  Borat your's is probably the same.  I'd have to check the Toro but I think flange on both sides. 

    The velocity out of a dual stage is 3400 to 4000 ft/min most common around 3700-3800 ft/min (that is if I am remembering those numbers right).  The better brands of machines will all be at the top of the high end.  Those numbers seem about right given what a Powerlite can do versus a dual stage in the back yard in conditions good for the Powerlite.

From reading the specifications, the KSK840, 845, 850  engines are very similar but have certain components that have different part nos. 
The  power output is as follows:  840= 4h.p., 845= 4.5, 850= 5, 870= 7 h.p. 

The HSK870 is apparently very similar to the 850 although, when comparing part numbers, I see some differences.  These are the most glaring differences.

                          HSK850              HSK870                
 Crankshaft         290684               290675
 Carburetor         640313               640300
 Muffler               390318A             390343

All other relevant components share the same part numbers including the cylinder assembly, crank bearings, connecting rod kit etc. 

I also noted that the above component numbers varied between the 840 and 850.  Got to wonder what going on? 

 Are the above  parts different from each other or, is it just a numbers change?  If the actual components are different, it's not hard to understand why Tecumseh went out of business.  Way too much parts differentiation between very similar engines.  And that's just their HSK 800 series.

I guess it's possible that on the 870, the crank might have been lightened, a larger main jet and freer flowing muffler put on to allow it to rev quicker/faster.  However, there's no change in the cylinder assemblies thus no changes to porting.  I can see those changes plus additional rpm bringing up the h.p. to 7 in the 870.  I've yet to see anything with an HSK870 engine in it. 

Here are a couple links if anyone wants to check the parts numbers.   Note that the first link prices are much better than Partstree.

http://www.absolutemower.com/pages/OemParts#%2fTecumseh_Power_Company%2fHSK870-8701A%2fEngine_Parts_List%2fHSK870-8701A%2fEHSK841HSK8XX8701A-EN

http://www.partstree.com/parts/?lc=tecumseh&mn=HSK850-8317C&dn=EHSK841HSK8XX8317C-EN

Comments?

Looking in the Technician's Manual I posted in another thread, the HSK840 and 850 list the same bore (2.437") and stroke (1.812"). The HSK870 is not covered in that manual, I couldn't find much about it. But if the 840 and 850 have different crankshafts, that would seem odd, given that their power #'s are similar, and they have the same stroke. Maybe it had something to do with the ends of the crankshafts? Different output diameters or something? It seems reasonable to me that the carbs might be different (different jet sizes or something?). But why the mufflers would be different from 840 to 850 is somewhat beyond me. Unless the 850's muffler was adjusted to allow better power production at higher RPMs?

Do they say what RPM they reach those HP numbers at? It might just be an advertising thing - add a few RPMs and get more HP, but not have any more power.

RedOctobyr: “At a given RPM”

    OK, got it, reasonable and valid.  One hp & rpm getting one torque value.  No cheating….

 

The charts are hard to follow but can be zoomed in go get the values.  All you need is one and can guess the others as they just increment.

The top right is FT LBS (the solid lines across)

Lower left HP

The top right Newton Meters (the dashed lines across)

The bottom right HP in kW

The bottom RPM

 

The top line is torque.

The middle line is Maximum B.H.P & kW

The bottom line is Recommended Maximum operating B.H.P and kW

 

Red, “If anyone finds better copies somewhere else, I'd be curious to find out where.

Below for a readable PDF with many engines.  Has HSK600, HSK845 but no HSK850.

http://th.manualwebsite.com/pdf/engine_and_accessories_2001.pdf

 

   On the chart you posted. How did you that?  It looks like a jpg. It looks to clear to be a screen capture.   Did you save the XL  as a .pdf and convert it to .jpg?

 

Borat, “Way too much parts differentiation between very similar engines”.

    Not sure exactly which component numbers but…  Sears would order a cover and choke special for their machines.  That would boot those numbers and the final engine assembly.  In some cases Sears would order a lesser crank for their engines for a price break.  Ariens would require small mods at times.  MTD would have a PTO extension on the cam.  Murray used double pulleys with stepped cranks ends again causing number changes.  There might be 50-100 variations on a HSSK80 in a year.

   A few times on a rebuild the bore and piston values did not match the Tecumseh spec for that engine.  Possibly the engine was a dash model ordered on special.  ??

 

Red, “Unless the 850's muffler was adjusted to allow better power production at higher RPMs”?

   A manf requesting a muffler change is not uncommon.

 

Bill, “Do they say what RPM they reach those HP numbers at”?

    The final RPM value in the charts Red posted are all 3600.  In the manual above the spec’s use 3200 and 3600.  I think the 32’s are lawnmower engines.

 

Red,

   More comments about the Amazon type tach...  There are scads available with that case type.  Some variations are replaceable batter or sealed case, with and without a ground wire, and various arrangemens of wire ends like clips or no clips. 

   Mine were low end and listed as replaceable battery but the case was sealed.  They did not come with a ground wire but I installed ground wires in them.  No end clips but I installed those also.  The readings as I mentioned were not that reliable until the ground wire was put in.  The reading update was ok but no that fast.

   Today I installed one on a single stage.  I only attached the sense lead without ground to check it out and the readings were excellent with a much faster update on rpm changes.  ??  It was never that fast before even with ground attached.  The difference is probably a better signal to the RPM gauge for what ever reason like cowling or less noisy plug..??  Works like a charm mounted to the carry handle with tape. 

I really like the Treysit sirometer. 

That thing is uncannily accurate.   I set the rpms on my Toro with a Tiny Tach and compared the reading with the sirometer.   About as close as you can get.  They are, without a doubt one of simplest and most useful devices I've seen for measuring rpm and/or cycles per second.  No batteries, no wires, no complications.  The only downside is that you need to use both hands to operate it and you need a big enough spot to place it on the machine being measured.   It's also perfect for measuring RPM on my diesel  power plant.

Some participants will remember Jubol, a great guy who passed away about four years ago.  He's the guy who clued me in on the sirometer. 

Rest in peace Jubol.   

trouts2, it's  somewhat interesting (to me, at least): The last few times I've used my digital tach/hourmeter, I've had some issues with the screen suddenly going from RPM to "11111" then "2222"..... counting up towards "99999". I can't figure out exactly what's causing it. It will usually go back to an RPM by 4 or 5. I *presume* it's caused by an iffy signal to the meter. Maybe it's from the RPM changing? As I recall, the engine isn't necessarily hunting while it's doing this. Usually, when I've been using it recently, I've been doing it quick-and-dirty. Mine has no connector on the spark plug end (wraps around the wire a few times), then it has a round connector you put under an engine bolt. To make things simpler, I've been clipping an alligator lead onto the ground connector, and clipping the other end onto a cooling fin. Perhaps that's part of the cause. I've never actually tried disconnecting the ground entirely.

borat, what you're describing sounds like what I've heard called a Vibratach? I've heard good things about them, but never seen one used. I bought my tach/hour meter for about $30 a few years ago, because it did both functions, could be mounted so you can keep an eye on the RPMs while using the machine, etc. But what you're describing does admittedly sound interesting. With an eye towards my own potential use for something like that, can they be used on chainsaws? And what RPM do they reach? The saw is supposed to be 13,000.

http://www.machovec.com/quest/vibratach.htm

Sirometer and Vibratach are the same.  They can be had on ebay for around $20.00.

The one i have is supposed to go to from 800 to 50,000 rpm.   


It will work on a chainsaw but it would be a bit tricky to run the saw wide open and hold the sirometer on it at the same time.  A chainsaw running at 13000 rpm and not having the bar in a log, can be potentially dangerous.  It that situation, I use the Tiny Tach.   It's nice to have one of each.  If the electronic device fails, you know the sirometer won't.  I know my Tiny Tach doesn't  like cold temperatures.  It can be a bit iffy when it's cold.