I think I got a fuel issue here

[KE4AVB]

Briggs 331877-2371-G5

I trying to repair a problem that another shop introduced and refuses to fix for one of my customers. Boy I hate trying to fix a DIYer repair shop problem.

The engine misfiring at idle speeds when I can get it down to 1750 rpm. It randomly try to kick the engine backwards. I do know it has a dang Chinese carb stuck on it. I got to run fairly smooth but that is a 2500 rpms which is no near idle speed. I did try adding choke at full throttle and the engine runs better partially choke.

I just wondering if I have a pre-ignition problem due to it running so lean or is possible that I have also a failing ignition coil as it had been rubbing on the flywheel too. I be pulling that Chinese crappy carb off this morning to check the main jet size as know the Nikki that should be on it has a 1.15mm main jet according to my in-house PN to jet size check chart. I hoping that this is the problem and that they cloned the jet area as a regular Nikki carb. If so then I can install the correct jet size.

I got to see if my machinist has both the #57 and #56 drill bits to the jet size. The #56 would make the jet a 1.18mm [792296] but the IPL is calling for a 1.15mm [796251]. I got to find metric micro bit set somewhere reasonable.

#57 .0430
1.10mm .0433
1.15mm .0453
#56 .0465

[KE4AVB]

I found a 1.18mm jet here and that is not the problem.

It turns out to be the non replaceable idle jet that I am currently resizing. It was just under #75 bit, I am now at #74 and it is nearly there. Going up one size [#73) which should be enough. It is definitely a lean burn issue causing the back spit [cough]. This something I ran into a couple years ago when I had an intake gasket leak but it was just sneezing instead of coughing. Hmmm I violating EPA rule against carburetor modification.

Darn couldn't be left the way it is was as it would have destroyed itself sooner or later. I just chalk it up to another reason not to buy Chinese cloned carburetors; not worth the trouble they cause.

[Skywatcher]

Hi KE4

On the subject of these Chinese carburetors, are the ones sold through Oregon and Stens built to a higher spec than the ones you can get through Amazon? I've replaced several carburetors on Tecumseh and Honda engines with ones bought through Oregon and Stens with out any problems. Any thoughts on this?

Sky

[KE4AVB]

Don't know Sky. Most of the ones I tried were through my distributor A&I (Formerly Sunbelt Outdoor Products). I now actually gun shy of any of them.

Kinda wish I had a 0.6mm drill bit kinda better just to leave things as they are now as it running good. It is borderline lean now as it just surges a little when first started. I have gone .0015" larger. Another .0015" might be too much. Right now I at #74 (.0250") the next closest step is the .6 mm (.0236") and the #73 is .0240"