Lawn Boy engine

[Russ2251]

Good eye Mr. Jerry.
What you see there is a 1954 model 8 and is actually very useful. Not original carb. Starts on 2nd pull. Will push my cart low 20's. Great for kids.
I have too many engines to list here. Some are 'kartable', some are not. One of them is a 1947 Briggs & Stratton model ZZ. It's 8 hp and weighs about 130lbs and is one of my favorites. Was used on big tillers and small garden tractors. If any one is interested I can post pics and/or video on YouTube.

 

[Russ2251]

Mr. Kibble:
First of all...Congrats (I think).
Second, while you have DuraForce disassembled, it would be a good time to make a small but effective modification to increase compression ratio and therefore horsepower.
Eliminate head gasket and use a good high temperature flange sealant such as that pictured.
This will decrease space between head and cylinder block and will give a small boost to horsepower.
I took measurements first (using modeling clay) to make sure there were no clearance issues such as piston crown slamming into head especially around circumference of piston crown/cylinder head edge.
Anyway, sealant should be spread thinly (to one surface) and if done properly will ooze out a small amount (4th pic) once it is torqued to specification.

 

[ed1380]

vrooom. hemi

 

[Russ2251]

vrooom. hemi

Yup...and you thought Chrysler invented it.

 

[kibble]

Oh, I decided working on that engine was going to be too much, so I threw it away.

 

[Russ2251]

Yeah....and monkeys fly outa my butt!!!

 

[kibble]

LOL!!!! No, I just haven't had time to get down and dirty with it. But I'm taking all your little tips into consideration.

 

[Jerryburger]

Kibble- I just about choked and thought "He's gotta be kidding!". Too funny. My poor B/S 2-stroke sits stagnant too, for now. Sorta off topic, or adjacent to it...
Do the Lawnboys have the lighter flywheel, being that they're pretty much designed to swing a lawnmower blade? And, if so, was there any issues with getting it to idle decently without the added inertia of the blade?

 

[Russ2251]

Do the Lawnboys have the lighter flywheel, being that they're pretty much designed to swing a lawnmower blade?

The older model D's all have the light aluminum flywheel while the model F's had aluminum as well as the heavier zinc.
The heavier zinc flywheels were only used on BBC mowers.
BBC stands for Blade Brake Clutch. These models had a 'lockout' that when released disengaged a clutch and applied brake to spinning blade while engine continued to run.
This offered the convenience to stop mowing without having to restart engine. A spring loaded bale had to be pulled back to release brake and engage blade through a clutch. These BBC engines are unusable for kart use (shortened PTO) but modified heavier flywheels can be salvaged and used on the kartable engines.

And, if so, was there any issues with getting it to idle decently without the added inertia of the blade?

I had some problems with aluminum flywheels early on (stalling) but solved them by tweaking carb adjustments. Slightly leaner low speed and slightly higher idle RPM. I no longer use the heavier flywheels.
Keep in mind that there is a slightly higher risk of flywheel explosion with zinc than with aluminum. Aluminum can take about 7,000+ RPM with a load. Proper torque spec on flywheel nut is paramount. Too low torque will cause key to shear while too high torque can cause warping and/or fracturing.

 

[Jerryburger]

COOL! I was kinda wondering what to expect from my B/S 2-stroke. I only had it running briefly, but I don't remember it giving me too much problem idling.

 

[Russ2251]

YouTube Video Lawn-Boy DuraForce cold start engine test

Ready to mount on kart. Clearly has more stones than original model 'F' conversion.
Smokey exhaust due to temporary rich carburetor settings.
Head gasket removed to increase compression ratio/HP. Probably around 7 HP.
http://www.youtube.com/watch?v=grpR-T_vbE8

 

[Jerryburger]

WooHooooo! That thing BARKS! What's the displacement, compared to your B/S snow engine? Lordy are you gonna have fun with that! Gonna need a longer drag-strip!

 

[Russ2251]

WooHooooo! That thing BARKS! What's the displacement, compared to your B/S snow engine? Lordy are you gonna have fun with that! Gonna need a longer drag-strip!

Identical specs to Briggs with 141cc. Just reed induction as opposed to piston ported. Reed engines tend to run higher RPMs with a few exceptions.

 

[Jerryburger]

So is it pretty much ready for the kart? I'm kinda getting anxious to see that thing scoot!

 

[Russ2251]

So is it pretty much ready for the kart?

Yup...just 'Plug n Play'.

 

[I like karts]

BBC stands for Blade Brake Clutch.

What???

I thought it was a British TV channel

 

[Kenny_McCormic]

Mr. Kibble:
First of all...Congrats (I think).
Second, while you have DuraForce disassembled, it would be a good time to make a small but effective modification to increase compression ratio and therefore horsepower.
Eliminate head gasket and use a good high temperature flange sealant such as that pictured.
This will decrease space between head and cylinder block and will give a small boost to horsepower.
I took measurements first (using modeling clay) to make sure there were no clearance issues such as piston crown slamming into head especially around circumference of piston crown/cylinder head edge.
Anyway, sealant should be spread thinly (to one surface) and if done properly will ooze out a small amount (4th pic) once it is torqued to specification.

Neato, I need to get me some of that sealant and do my briggs. How much did that tube run ya?

 

[Russ2251]

How much did that tube run ya?

I don't recall...probably around $5-$6. Permatex and Loctite may have same part number (25249 or 85249) and is same stuff. Please note that this is not an RTV (won't work) and remains 'gooey'. The thinner you can apply it, the better. You should see some slight seepage/ooze around entire circumference of sealed surface once it is torqued (modified 'X' pattern) to factory spec. Surfaces must be flawless in order for it to seal properly. Failure is guaranteed if there is any warping, contamination, oil, gouges, bumps, dings, dents, etc. Clean surfaces with alcohol.
http://www.permatex.com/products/Au...ng_Formula_Gasket_Dressing_Flange_Sealant.htm
"I" heads and "L" heads have different rules regarding clearances.

 

[crazycart]

Thats the stuff i use to seal motorcycle engine cases,works great.