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Lawnboy Gas/Oil Mix Ratio?

Posted by mxyplx (My Page) on
Thu, Mar 22, 12 at 19:14

I've a 1979 Model 4500 with a D410 engine (near as I can tell). Haven't used it for years. Last time, about '05, I mixt the gas with Moblie 1 Racing 2T Fully Synthetic 2 Cycle Oil of which I still have. Can't recall what gas/oil ratio to use.

What gas/oil ratio should I use?


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RE: Lawnboy Gas/Oil Mix Ratio?

  • Posted by baymee LehighValleyPA (My Page) on
    Thu, Mar 22, 12 at 19:24

The older models were 32:1, which is what I use in any Lawnboy.


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RE: Lawnboy Gas/Oil Mix Ratio?

That soumds familiar. Thanx. I sort of remembered 20:1, but it didn't feel right. Glad I asked.


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RE: Lawnboy Gas/Oil Mix Ratio?

'D' engines may require 16:1 if they have a non-roller bearing for the crankshaft or rod journal. 32:1 came in with the roller bearings. However, with a highly-concentrated synthetic oil, you're probably okay at 32:1 anyway. I used Opti-2 in my LB 10550 (Duraforce) at 66:1 for several years.


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RE: Lawnboy Gas/Oil Mix Ratio?

"I've a 1979 Model "
"Can't recall what gas/oil ratio to use"

32:1

Walt Conner


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RE: Lawnboy Gas/Oil Mix Ratio?

It ran OK after all those years. Started on the 3rd pull. It looks like I had MPteed out the gas tank and carb etc ie put it away properly. BUT!

I see why I put it away. The noise. Even with earplugs my head was throbing and I was tired just from that noise and maybe a bit sick too. I'll use it a couple times till I can fix my trusty Tecumsee. Maybe get some ear muffs over the plugs.

Kinda reminds me of switching from driving a 4-stroke Cummins to a 2-stroke V8 Jimmy - you need an attitude adjustment.


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RE: Lawnboy Gas/Oil Mix Ratio?

"The noise. Even with earplugs my head was throbing and I was tired just from that noise and maybe a bit sick too"

Must have a hole in the muffler. I have had dozens of LBs, generally quieter than 4 stroke.

Walt Conner


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RE: Lawnboy Gas/Oil Mix Ratio?

I'll check that out.


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RE: Lawnboy Gas/Oil Mix Ratio?

I think it has a cast aluminum muffler housing under the deck. There may be any or all of several things wrong. Look for the obvious, a hole in the housing as already mentioned. Failing that, you may be able to see where the exhaust is leaking by carbon where it shouldn't be. The exhaust goes thru the mounting plate into the muffler. There is a gasket at that interface. You might simply have loose screws. You need to remove the muffler cover anyway to check for carbon build-up in the exhaust ports and a clogged muffler. Considering it sounds loud, I'd guess it's an exhaust leak above the deck which possibly can be fixed by tightening the mounting screws after removing the muffler cover. If already tight, be careful you don't strip out the mounting plate/cylinder head threads - it could be the gasket is burnt up.
To remove the muffler you have to remove the blade adapter. This is usually done by tapping the square corner as if to try to rotate it. You probably should put penetrant on it overnight as they can be tough.
If you get it running right, you should make up a batch of fuel with Lawn-Boy oil and cut your grass a few times with it to experience that sweet smell of LB oil and toasted grass from the exhaust - this has become a treat from yesteryear that you have to experience. Also, never let it sit on the lawn running without moving - you will get burn rings from the exhaust.


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RE: Lawnboy Gas/Oil Mix Ratio?

I had disassembled, cleaned and reassembled the whole thing in 2005. So it should all be tight and sanitary. So all this is from memory. This will be only the 3rd maybe 4th time I used it. Yes it stank as I recall. Didn't notice that this time but it was windy. Blew the stink off? :-) It's a neat little mower- if I can get past the noise I'll use it.

I turned it up and the housing under (above?) the blade was solid as the Rock of Gibralter. Is that the muffler or is the muffler under that housing? I didn't want to pull it and disturb any gasket that might be there unless necessary.

There is a 1/8 Dia drilled hole in that housing which I presume is for water to drip out.

The few notes I have indicate to me that the carburetor spring is for 3200 rpm. I seldom run my Tecumseh at more than 1/2 throttle so it's noise is vastly reduced. I really think I'm just not used to the sound of the 2 stroker especially at 3200 rpm. It looks like I had tried to order a lower rpm spring (2500) and couldn't get one.

I know from experience after driving a Cummins or a Cat then switching to a Jummy 2 stroker you could wind em way up till it sounded like the engine would fly apart and it only be up to 900 rpm. That's embarassing really, one time I swapped trucks and hit first gear 3 times in a row b4 getting squared away.

So anyway is that housing the muffler or a muffler cover?


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