Potential Lawn-Boy tweaks - hand-lap reed, double crank seals, crankcase stuffing - Page 4 - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #46 of 53 Old 07-05-2019, 02:22 AM
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Re: Potential Lawn-Boy tweaks - hand-lap reed, double crank seals, crankcase stuffing

Quote:
Originally Posted by mtgrs737 View Post
I am wondering why you would need to tweak a LB engine? They are plently effecient for cutting the grass just as they are. Did you realize that the DF engine uses a tuned exhaust and a rear boost port?
I'm with you. If it is just cutting grass...well a properly jetted lawnboy or duraforce does it better that about anything else out there.
No reason to waste the time, effort, or even bother as they don't need the extra 5% hp or heat dissipation.
I would rather focus or obsess on one of the many other things I do that on...LOL

Now if you are using the engine for another purpose like so many Briggs were on go carts and mini bikes, then TWEAK TWEAK TWEAK away.
I was also, always the tuner who had his stuff running faster then the other peoples. Started with bicycles with sprocket changes and even rear wheels, then Puch mopeds with milling out exhaust port and opening up muffler, then motorcycles, then cars from 73 Buck Century with 350 2 barrel in it originally, to 67 and 68 GTOs with 400 Pontiacs.
I learned that if you opened the gap on the points to about twice as wide..It ran a lot stronger...until they burned up in about 10 days. But Standard Blue Streak lasted longer.
Learned how to tweak a Quadrajet and Carter ARF carbs. The air vane on GM is almost always to tight and jetting can be tweaked a lot after other mods.

Mowing grass is not something I do anyway. I fix mowers and test them for only a few minutes. As long as they run fine, I am good with that.

It never hurts to more fully understand how things work but there are times that "in theory" and in actual laboratory facts...things might be "better" but no real noticeable or worthwhile improvement in actual real world use.

Kind of like the old Splitfire spark plugs...."Up to 3.78% increased fuel mileage" if they did get full 3.78...that's an increase...sure is, but who really cares about that little bit. Were talking about 1990 when the mileage was probably 13-15 around town if lucky! I'm not going to bother to change them or pay 4.99 for them (autolite back then was .79-1.59) for the less than .5 mile per gallon....Not even if I can rationalize the savings if I keep them in for a little over a year and break even.
Cause in the real world...3.78% ain't gonna happen and if it does it will not maintain that level for long.

I actually use two in a KX750 Twin. They ran stronger for a bout 3 days and then about the same. That bike was cold blooded and popped and spit or about 8 minutes when cold. Put Bosch Platinum in and it started and idles smooth right at cold start. Not as powerful as with other or standard champions autolite etc but so much smoother on start up.

SO run run run that little lawnboy monster.
I stopped working on those around 2006 or 2007. I liked the duraforce last ones best. Hated the earlier ones with coils under flywheel IIRC and muffler under deck that clogged and needed exhaust port de carboned when they lost power. Never liked the rotating clicky throttle gov adj either. I guess I am nit wired for lawnboys because so many people love them.
I like the power and sound, but hate working on them.
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post #47 of 53 Old 07-05-2019, 04:21 PM
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Re: Potential Lawn-Boy tweaks - hand-lap reed, double crank seals, crankcase stuffing

Thank you

What is the least expensive way to ship an F series Lawn Boy engine with Flywheel.?

what size box and weight?
Thank you.
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post #48 of 53 Old 07-05-2019, 04:56 PM
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[QUOTE=27grains;12299915]Thank you

What is the least expensive way to ship an F series Lawn Boy engine with Flywheel.?

what size box and weight?

It feels like a long block f series weighs around 20 lbs or so. I dont know if the post office has a flat rate box deep enough for it to fit.

I would personally build a 2x4 and plywood crate just big enough to fit the engine if I were shipping one though. It's a little more time and effort but itll protect things a lot better.

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post #49 of 53 Old 07-05-2019, 05:49 PM
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Re: Potential Lawn-Boy tweaks - hand-lap reed, double crank seals, crankcase stuffing

USPS will give you their shipping limits and sizes. Seems I remember 50 pounds but do not have the size limits. I have had better luck using flat rate and priority than other cheaper methods. I could give the prices I have now but just go and get the correct ones from where you will be shipping. It cost me $50 to ship to me 2 25 pound Sears garden tractor from New England to Wisconsin in a flat rate box. Roger
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post #50 of 53 Old 07-08-2019, 07:58 AM
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Re: Potential Lawn-Boy tweaks - hand-lap reed, double crank seals, crankcase stuffing

About the thrust bearing and washers, I can't find a picture of them installed. Where exactly do they go? do they sit on top of the lower crank bearing? What prevents the washers from spinning?
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post #51 of 53 Old 07-21-2019, 12:14 PM
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Re: Potential Lawn-Boy tweaks - hand-lap reed, double crank seals, crankcase stuffing

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Originally Posted by Mike72 View Post
John, welcome to the forum. All my Lawn Boys have lapped reed plates, I've been doing this for the past 6 years. I made small lapping plates from cast steel for both D and F models. I consider this a standard procedure when I build a new engine or rebuild an old one. I does make a difference with better crankcase sealing and cutting down on fuel fog. (reverse flow).
I have been considering getting a piston coated by Swain Technology for a test engine. As you know the piston is the critical part in a two stroke and anything that can shield it from heat is a big plus.
Most of my work with Lawn Boys has been to identify wear points and excessive manufacturing clearances, then make corrections. I think the Lawn Boy engines are excellent, but can use some finishing touches.
About 4 years ago I started making new throttle shafts for all my D models. The original shaft fits too loose in the carburetor body and hence wears quickly and gets even looser, allowing air to enter.


Could you post pictures of lapping procedure?
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post #52 of 53 Old 07-22-2019, 04:28 PM
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Re: Potential Lawn-Boy tweaks - hand-lap reed, double crank seals, crankcase stuffing

Here are the pictures that I had previously posted. The first two pictures show a new F crankcase with the reed removed. Notice the machining tool marks left in the surface during manufacture. All F crankcases and D reed plates have marks like this to some degree. Lapping can remove these marks and make the surface smooth and flat giving the best possible seal when the reed closes. Because of space limitations I use a 1 inch diameter round lap for F crankcases, there is just enough room to move it around with the fingers during the lapping procedure. For D reed plates a rectangular lap works well. When lapping the lap must be held flat against the surface and moved in a circular figure eight motion as large as space permits. Notice there are still some slight tool marks around the screw holes, this is not a problem since no sealing takes place there.
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post #53 of 53 Old 07-22-2019, 04:49 PM
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Re: Potential Lawn-Boy tweaks - hand-lap reed, double crank seals, crankcase stuffing

Thank You
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