LawnBoy Model 4861

ede

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Hello, new here I have an older 2 stroke pusher ~1990 had since new. looking for advice on where to find a new carb and air vane assy original #683632 or replacement #684352. My throttle vane assy is shot. not sure if a rebuild is in order or just buy new. Mower has been great. Worth fixing. I had a lawn service in college (Early 80's)and we ran LawnBoys 8 hours a day. At the time they were the only machines that would hold up, Probably got about 3 sets of wheels before they were too tired to go on! Suprising longetivity considering my care and maintenance at the time was minimal at best. Gas and go....Any help is most appreciated....Ed
 

FuzzyDriver

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With regard to air vane ***'y, PartsTree.com worked for me. It has a Toro part number, and I haven't installed it yet. Actually, not sure which mower I was going to put it on. I have an '88, '89, and '92, all F Engines so I imagine the part I got from them would work for yours. It is P/N: 104-4430
 

ede

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OK, thanks FuzzyDriver, Found the spring on the vane was broken, maybe an easy fix. So I have one on the way, hopefully it tightens up the throttle shaft that seems to have a lot of play although I have no baseline for what it should feel like. Thanks again for your help.....Ed
 

ede

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Have the new spring. Anyone have a method for putting the right amount of tension on it before putting the air vane on? Seems I can put whatever tension I want by turning the little spring mounting piece clockwise winding the spring up. It seems pretty touchy and of course of course will affect the freedom of movement when it is running. Just want to get it close so I don't have to keep taking it apart. Thanks.......Ed
 

lewb

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Each click is 25 or 50 rpm, I believe its 50 but not 100 percent. Like you said clockwise increase tension and counter clockwise will decrease tension. Increase tension will increase Rpm. I have installed this spring serval times on a duraforce, I just run it, make an adjustment, keep doing this until I have desired sound from engine, usually using two fingers (both index fingers) to turn it. Also place throttle at full when setting spring tension.
 

ede

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Each click is 25 or 50 rpm, I believe its 50 but not 100 percent. Like you said clockwise increase tension and counter clockwise will decrease tension. Increase tension will increase Rpm. I have installed this spring serval times on a duraforce, I just run it, make an adjustment, keep doing this until I have desired sound from engine, usually using two fingers (both index fingers) to turn it. Also place throttle at full when setting spring tension.

OK thanks LewB. So I installed the spring with just a bit of tension, put the carb back on gave it 2 clicks and fired up the mower. It seems to be running great. Better than it has in years. I did not know that the spring was adjustable so I'm sure it was too loose for a long time. Right now full throttle is 3600 RPM and powers through thick grass without hesitation. Thanks again for your insight and advice. Anyone know if 3600 is about right? Doesn't seem to need any more and sounds good.......Thanks Ed
 

lewb

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OK thanks LewB. So I installed the spring with just a bit of tension, put the carb back on gave it 2 clicks and fired up the mower. It seems to be running great. Better than it has in years. I did not know that the spring was adjustable so I'm sure it was too loose for a long time. Right now full throttle is 3600 RPM and powers through thick grass without hesitation. Thanks again for your insight and advice. Anyone know if 3600 is about right? Doesn't seem to need any more and sounds good.......Thanks Ed

3600 does sound high, what kind of tach are you using? I am think about getting one that uses a laser where you have to place a piece of tape on the shaft. Might need to get a service manual for your particular model, I think my M series runs at 3100 to 3200 and pretty much the same for my dura-force.
 

ede

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3600 does sound high, what kind of tach are you using? I am think about getting one that uses a laser where you have to place a piece of tape on the shaft. Might need to get a service manual for your particular model, I think my M series runs at 3100 to 3200 and pretty much the same for my dura-force.[/ is an

My tachometer is an Echo PET 1100, I checked with both non contact and with the antenna jack on the plug wire and got about the same reading 3500 -3600. I agree 3600 seemed high so I revved it down a bit when I mowing with it, I was just checking what it's max was with the carb settings as is. I have the original paperwork, haven't looked at it. Might not have that kind of detail. I'll probably just leave it as is and run it where it seems comfortable. Thanks again.....Ed
 

FuzzyDriver

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One of the parts sites has a tab for specs. I can't recall which one off the top of my head. I copied these specs from it:

Height: 1" to 3" in 0.4 " increments
Speed: 2900 +/- 300 RPM
Ignition Coil Airgap: .01"
Sparkplug: Champion RJ12C at .035"
 
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