Nozzle/Needle Value to use on Walbor LMT?

[Retired Pedler]

I just read a similar post on another forum. The question was not answered by anyone. Some of you professionals or others may know and can give some details on this one.

I just received a carb kit for an old Walbro LMT carburetor I wanted to repair. The engine it fits is a old 15 1/2 HP off an old Craftsman, I bought new in 1997. No,
I don't have the model number handy at this time, will have to look in the morning for it. Engine does not have a fuel pump.
The carburetor kit came with 4 nozzles/emulsion tubes. All 4 nozzles/emulsion tubes-have different size holes in them. I believe this is the main jet?
I had to remove the old nozzle/emulsion tube by drilling it and using a easy-out. It had been in there 18 years and not easy to get out.
I did check the hole jet size first and remember is was close to 2 millimeters. The tubes in kit appear to have that size and some down to close to 1/2 millimeter.
Also, kit came with 2 needle values for the float. A rubber tipped one and steel tipped one. The kit had no instructions off any kind, in it.


Question (1) : Which size nozzle/emulsion tube to use and the effects of using the wrong one on the engine? (Maybe better gas mileage?)
Question (2) : Which one of the float needle values to use? (My old one was rubber, but I would like to try the steel tipped needle value.)

Thanks! Everything else is running fine, thanks to everyone's help here. I am old and retired, so go easy on me...

 

[bertsmobile1]

For the float needle it is rubber on metal
So if it has a rubber seat ( which should also be replaced ) you use the solid needle.
If it has a metal seat, you use the rubber ( Viton or Byutal ) tipped needle.
Back when your engine was new B &S engines sold in 1/2 Hp sets all with the same piston stroke & head.
The difference in them was the main jet and emulson tube

 

[Retired Pedler]

Thanks for the quick reply from Australia.

You are saying this engine could come in 4 different HP ratings, depending on which nozzle is used in the carburetor?

Would not the use on the engine have a bearing on what nozzle is used?

 

[bertsmobile1]

Nope.
The manufacturers asked for an enine with X horsepower for a specific application.
B & S supplied them.
How B&S go the extra horses was no concern to Sears, all they wanted was X horses, as cheap as B&S can supply them.
So B & S do groups of enines with changes to the carb, fuel efficiency is not a selling point on residential mowers but power is.
So they just fit bigger and bigger jets till they get to the limit of the engines breathing.
Don't take my word for it download the parts breakdown for the 16, 16.5 , 17, 17.5 & 18 Hp engines and you will see that then only real difference is the cowel, the jetting ,occasionally the counter weights & some times the govenor springs but basically if it has the same bore & sroke then the "power" difference is all in the carb.
Remember we are dealing with very low power / cc engines.
A 500 cc single cylinder motorcycle engine will run 35 to 60 Hp
A 500 cc single cylinder mower engine will go 19 to 25 Hp

 

[Retired Pedler]

Thanks! to Bertsmobile1-from Australia.

I was wondering how B &S had some many different engines very near the same size and horsepower.
What you stated makes a lot of sense. It also reduces the tooling costs to build.