Briggs carb problem

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Russell

Russell

Well-Known Member
Apr 19, 2009
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I installed a walbro carb from a briggs & straton lawn mower on my 4.75 HP 2 cycle lawnboy engine. Works great up to 1/3 throttle. after that; it wants to die. Checked the float and fuel supply and they are fine. I am thinking that the jet marked (28) is two small.
The engine had much, much more top end with the old carb before it got damaged.

Any other thoughts on what else could be the problem?
Anyone familiar with walbro jets?
 
Last edited:
xseler

xseler

Well-Known Member
Apr 14, 2013
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OKC, OK
The Briggs carb was made for straight fuel. When you change to a 2 cycle mix it's gotta throw the calibration off.

Kinda like sucking milk through a straw ---- now change the milk to a milk shake. Notice the difference?

Good luck with your issue!
 
Russell

Russell

Well-Known Member
Apr 19, 2009
1,276
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Well sounds like I might as well try opening the jet first before scraping the carb altogether.
 
Russell

Russell

Well-Known Member
Apr 19, 2009
1,276
155
63
MA
The replaceable carb jet was marked 28. I assumed that the orifice was .028, I opened it to .040 with a drill bit.
Now the engine works great. A small amount of 4 cycling at idle but that goes away as soon as take off. This bike really flies.
 
silverbear

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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northeastern Minnesota
Russell,
I can't remember a build thread using that lawnboy engine. Did you do one and if so, could you give the link? A couple of years ago Curtis Fox and I were thinking about the lawnboy as a good candidate for a bike engine. I'm glad to hear that it's working out and that Briggs carb is working for you.
SB
 
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