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Abby’s Guide > Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) > Discussions > Craftsman 5/21 Single Stage Experiment

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borat


Joined: Nov 10, 2007
Points: 2692

Craftsman 5/21 Single Stage Experiment
Original Message   Jan 17, 2011 2:24 pm
I finished cleaning the carb, and the going over the rest of the machine.   Then I made a simple modification to give me a considerable increase in power.  I connected a  piece of nylon string to the top of the "L" shaped lever that controls the governor.  I drilled a small hole through the bottom shroud on the left hand side and fed the string through it.  I tie wrapped the string to the handle of the machine up near the top where it bends to go horizontal.  I tightened the tie wrap to hold it's position when moved up or down the handle thus keeping tension on the string as required.   From readings I was getting on my Tiny Tach, this simple modification allows me to increase engine rpms to  a bit past 7500 if I want.  By sliding the tie wrap up or down, I can dial in the engine speed that works best for the conditions.  

Performance is very much noticeable.  At stock engine speed of 3500-4000 rpm, the machine will throw moderately dense snow maybe 15'  if I put the revs to it, it sends it at least 20 to 25 feet or further.  I really don't understand why manufacturers spin these two cycle engines so slowly.  They love rpms.   My little Toro power shovel runs around 8000.    Could possibly be for longevity purposes.  I'm not too concerned about that.

Overall, for the little I paid for it, it's a good machine.  Starts first pull and runs solid. 

What I have noticed though, is that this machine doesn't like to go up 10% grades without assistance. 
Replies: 1 - 4 of 4View as Outline
MN_Runner


Location: St. Paul, Minnesota
Joined: Dec 5, 2010
Points: 622

Re: Craftsman 5/21 Single Stage Experiment
Reply #1   Jan 17, 2011 3:09 pm
Borat,

There is nothing magical about 8000 RPM.  How about 10,000 RPM, which is slightly faster than the Lexus LFA's redline?  My old Civic SI had a redline of 8000 RPM.  As you approach 10,000, please roll your video so we can watch it when you are ready to show it.

Paul7


Joined: Mar 12, 2007
Points: 452

Re: Craftsman 5/21 Single Stage Experiment
Reply #2   Jan 17, 2011 3:36 pm
borat wrote:
Overall, for the little I paid for it, it's a good machine.  Starts first pull and runs solid. 


Sounds like a winner.  It's also great to have a backup machine.  No matter how well we maintain our snow blowers they are still machines and capable of failing us at the worse possible time.  I've seen many a neighnor have their snow blower in the service position in their garage during a snowstorm.  I'll always have either a small 2 stage or a single stage (if I ever find one that works) as a backup.
borat


Joined: Nov 10, 2007
Points: 2692

Re: Craftsman 5/21 Single Stage Experiment
Reply #3   Jan 17, 2011 5:55 pm
MN_Runner wrote:
Borat,

There is nothing magical about 8000 RPM.  How about 10,000 RPM, which is slightly faster than the Lexus LFA's redline?  My old Civic SI had a redline of 8000 RPM.  As you approach 10,000, please roll your video so we can watch it when you are ready to show it.


A man's got to know the machine's limits. 

Ten grand with static timing likely wouldn't be very healthy for the engine.  I think 7500 rpm is more than enough for an old piston ported Tecumseh.  After all, it is an OPE engine designed to run at half that speed.  

I've got 1970s Yamaha RD350 and RD400  twin cylinder motorcycles with state of the art programmable ignition systems in them.  I run them to 10K making juice all the way, with no ill effects.  
borat


Joined: Nov 10, 2007
Points: 2692

Re: Craftsman 5/21 Single Stage Experiment
Reply #4   Jan 18, 2011 10:17 am
I took the Craftsman single stage out this morning to clear about 18" of eod snow.  I cranked up the engine to about 6000 rpm and I was  surprised how well it threw the heavy slush/snow.   Not sure I'd want to tackle much deeper but it sure moved this stuff.   
This message was modified Jan 18, 2011 by borat
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