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

Guys,

I may get to go check out some SS's. One is a Yardman 21" 5hp 2-stroke. The other is a Toro CCR2000e 2-stroke.

I am leaning towards the Yardman, based on boratification possibilities. I'm guessing/hoping it has a 5hp Tecumseh, maybe the HSK850. The Toro would have a 4.5hp Suzuki engine, from what I understand. I don't care about electric start. Any reason to avoid the Yardman? I realize it's probably not as solid/durable a machine as the Toro. But if it could be ramped up more in the power department, I could live with that. Thanks for any feedback.

trouts2 wrote:
So, if I'm reading that right, are you saying there were HSK850's spec'd at 4500? Just curious because that's what I currently have mine set to. If that was an officially-sanctioned speed, that would be nice to know (I wouldn't feel that I'm pushing the engine as hard).

As far as crank weight, I'd expect:
- If the change was to a counterweight, the change might be to help properly balance out pistons & connecting rods with different weights (but it doesn't sound like there were different versions of those?)
- If it were a "nonspecific" weight change, I'd expect the extra mass would primarily act like a very small flywheel addition. It could help the RPM stay a bit more constant through small & quick loads. Flywheels only help smooth the quick bumps & dips due to changing engine loads. They won't help for prolonged added loads (a bigger flywheel will just make the engine take a bit longer to slow down). But a crank change would do much less than a true flywheel, and would make a very  small difference, I'd think.
- I presume the difference is not just due to differences in the PTO area (different length & diameter sticking out of the engine, etc)?

So, if I'm reading that right, are you saying there were HSK850's spec'd at 4500? Just curious because that's what I currently have mine set to. If that was an officially-sanctioned speed, that would be nice to know (I wouldn't feel that I'm pushing the engine as hard).

 

   Oops, that should be 4300 Max from factory 4000 +- 300.

 

The following from Tecumseh manuals.  These manuals predate later maker models past 2002 which have mostly been rpm bumped.

 

HSK600

Toro      290607,  fixed speed top governed speed 4500

MTD      290609, fixed speed top governed speed 4700

Snapper 290607, fixed speed, top governed speed 4500

Toro       290602, fixed speed, top governed speed 4700

Murray   290607, fixed speed, top governed speed 4500

 

For HSK845 also listed as TH139SA (<<<---same as HSK850)

MTD      290614, fixed speed, top governed speed 3800

Toro       290681, fixed speed, top governed speed 3850

Service   290627, fixed speed, top governed speed 4000

 

   For some reason they have tied these spec's to a given crank.  I have HSK600's with these cranks so it looks like I'm legal for 4700.

   For reference on the HSK870 to HSK850 crank difference it was 2.825lb (870) vs 2.481lb

 

>>I presume the difference is not just due to differences in the PTO area (different length & diameter sticking out of the engine, etc)?

 

    For the SHK870 vs 850 difference I don’t know where the wight diff is.  I have seen 8hp crank differences in the lobe masses next to the journals.  The lesser crank was on a Craftsman so I thought it might be to cut the crank cost but just a guess.

I got to play around briefly today with boratifying the Yardman. I tried tying a string at the upper governor linkage connection, where it goes to the throttle plate. I ran it through an existing screw hole in the lower housing (which was already missing its screw and open- if that's not a sign to boratify it, I don't know what is ), out the side of the machine, and up to the handle, where I tried attaching it to the bail.

I liked how it worked. Squeeze the bail, the RPMs climb; let go, and they drop. For the way I tend to use it (squeeze then release at the end of a run), that sounds good. I could lower the fixed-governed speed to even below-stock (for warming up, etc), and keep a high speed for doing work. I didn't have much time to mess with it, and I don't have any springs sitting around, so I need to revisit this. I'd like to add a spring, and perhaps something like a turnbuckle adjuster, or some other means to make controlled adjustments to the high-speed setting.

I was at Home Depot yesterday and took a look through their OPE-parts section. They have a universal throttle assembly (lever and cable) for $7. That could be a pretty convenient way to add a control that you can simply set & forget. An advantage over simply pulling a string by hand is that the lever would reach some maximum setting. Once properly adjusted, you couldn't accidentally take it to 9000 or something (that would be my fear if I was yanking on the string manually. Have it catch on my glove or something, and send the RPMs to the moon). Heck, with an appropriate-stiffness spring between the throttle cable and the governor, you might be able to make it such that lowering the lever would give you a nice idle, and you could perhaps use pretty much the whole range of the lever to adjust your speed.

I'm not knocking your approach of simply pulling on the string, borat. That's simple, cheap, effective, etc. Just trying to tweak it slightly based on what I think will work better for me. For all I know, I could get this sorted out, then find out you really need the ability to adjust the high-RPM's on the fly, for heavier/lighter snow.

Hey, Red, it's your machine to do as you wish.  All the power to you.  Just let us in on your mods.  Always enjoy to see what tricks guys are cooking up for their machines.

I don't think the 139cc Tecumseh engine can rev past 6500 rpm.  I pegged mine for a couple seconds unloaded and that's about it's limit.   I think the exhaust ports are probably  the most restrictive part of the system.  Those three little holes are pretty tiny for 139 cc engine.  If you ever saw the exhaust port on a 125 cc motocross bike engine, you'd know what I'm talking about.  They're positively huge by comparison.  You can stick a fresh bar of soap through the exhaust port on those things. 

    It's 50+ here and feeling like summer.   Out putzing with the machines and noticed the MTD 7hp SS had the cowling bolt but no support bracket.  It's an earlier model like Red's.  They probably did not come with with engine supports like later models.  The bar the clamp is on is a stablizing bar welded to the side of each intake housing side. 

   The brown bar is the wheel axle.  In later models they removed the stablizing bar and left just the axle which is where the bracket runs to on later models.  The bracket connected the axle, engine and back of the intake housing making a nice brace.   The added bracket is a RedOctber-like motor stablizer out of a steel steel.  Can't see the bolt and nut very well as they were slimed with grease.  The brace dampens the engine considerably and even noticable at the handles.  Probably would never had added it if I did not see Reds.   

   It's a 7hp now as it got update 803554, RMP Enhancement String Kit.

Trouts:

Are you using the high speed nylon braid or the super slick over-drive mono line?

I have one of each installed.  Despite all the hype, I've not noticed any discernible difference in output between the two.  Sure, the bright yellow mono looks spiffy but it doesn't tie as nicely as braided.  However, I do think I'm getting better fuel economy with the mono.

Borat,

   I"ve actually been looking for better string like a tight braded nylon but thin. 

   I had set a few of the machines to have a base rpm higher than normal and the string to max it from there.  Running it like a chainsaw seemed a good idea so I lowered one way down and ran it like that for a while.  Funny stuff as it is like using a chainsaw and gives the engine a break so I set the other machines the same way.   

   It's 40 here in the shade today so will probably get to the low 50's.  It'll be in the 50's next week also.  It's looking like no possibly snow here at lest into March.  Very frustrating.

Nice mount, trouts! I thought about using sheetmetal, but I didn't really have something like that handy. So, ironically, making it out of aluminum was almost easier. It was more fun, at least, I got to machine it

I'm on board with what you found, in terms of raising RPMs. I haven't yet gotten to play with my string setup any more. But I did pick up a spring to add to it, and a turnbuckle for easier adjustability. I want to add them to the machine, then maybe I'll try to get some pics. I have the string going to the bail, so as the handle gets close to fully squeezed, it raises the RPMs. I haven't yet lowered my governed-RPM speed, but that's on my list. I took the governed speed from 3900 to 4500. I will probably lower it back to 3900 (stock), maybe even lower. And try to adjust everything so that squeezing the bail is enough to crank it up to a feisty operating speed.

I'm using general purpose braided nylon string. Excuse me, Ultra Performance Turbocharging RPM Adjustificator Space Age Polymer Cabling. My string is just white. But if I dyed it red, that would add another 0.25 hp and 1" of cut width right there. You did have me wondering what 7hp MTD you were referring to, until you listed the part # and explained the upgrade And borat, you're probably right, the mono line will give you better fuel economy vs braided, as it reduces weight, and will have less wind resistance. If you polish the line, that will also help reduce drag as the machine is moving forward. +10 points for bragging rights, however, if the line you're using has a tensile strength greater than the weight of the machine.

I found that adding NOS stickers at the appropriate places can increase torque or horsepower.  You just move it around until the engine feels right for your application.  It's kind of cool to tune the engine by just altering the placement. 

Early last year, I put in application  with the Canadian Federal Government to purchase a piece of "militarily sensitive" Spectra space tether.   Putting that on the Craftsman would make it deliriously awesome......

The package finally arrived and I was quaking in my boots to see this stuff.  I feverishly tore the box open only to find that they sent me a piece of binder twine? 

I think they're testing me to see  how much I know.