4.5 HP Lawn Boy: Russ

[VoodooChild]

I think i remember hearing you say that only the duraforce had reed valves, and that's what made them have more horsepower. However i just got around to tearing down 2 of my 4.5 HP silver series lawn boys. And was surprised to find reed valves in both of them (havn't checked my third one yet) Also i found needle bearings in the crank/rod, and crank/case. Seems like these would be pretty good engines (i also did acquire a duraforce recently, but havn't started with that yet). I wonder what makes the duraforce an extra 2 horsepower better, displacment? or just the sticker

Also i'm looking to get some carbs for these engines, as i'm soon going to get some mounted (have a comet cvt for one of them)
And was wondering if the tillotson hl 299a are similar to the 239b, or any good for that matter. I can't seem to find what the heck the numbers mean, i guess the letters are just different versions of the same carb: newer years.

Heres some pics of the engines

 

[Russ2251]

I think i remember hearing you say that only the duraforce had reed valves

Never said that.
ALL Lawn-Boy mower engines are reed inducted except for the model "M".

Also i found needle bearings in the crank/rod, and crank/case.

Yup.

I wonder what makes the duraforce an extra 2 horsepower better, displacment? or just the sticker

The former, among other things.

And was wondering if the tillotson hl 299a are similar to the 239b, or any good for that matter.

Unknown to me. Trial and error got me running. Look for a .750" venturi based carb. Does not have to be Tillotson.
Make sure NOT TO MIX CRANKCASE HALVES or ROD CAPS. Assemble them exactly as they came from the factory.
Download manuals (PDF) if you haven't already done so.

 

[VoodooChild]

Got it, thanks.
Gonna work the duraforce first, and try to get it mounted to a 70's motobecane moped, possibly with TAV 30 series. If that works out, i'll have to decide whats next.


Has anyone figured out what the numbers after tillotson hl mean?