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I bought the Snapper RER that was running rough. When I tried to start it some times gas would come out of the carb intake flange, O ring leaking! I did a rebuild on the Chinese Nikki copy' including the tiny, tiny O ring on the main jet that came from the Kohler rebuild kit for Nikki carbs. That helped but it was still surging at idle until I closed the fuel supply valve, then it would idle smoothly. My neighbor that's pretty good with small engines said that the knock off carb is slightly flooding still. I had read that most surging with the Chinese carbs were fixed by enlarging the idle jet oriface but I think that I was getting too much fuel. I cant find a Walbro that is listed on the parts website as unavailable but I found a genuine new old stock B&S 799728 by Nikki that was listed as the gravity feed carb for $40 on Ebay and got it. I replaced the two O rings that usually fail and result in flooding with Viton O rings and installed a better fuel filter to hopefully avoid problems. I replaced the Chinese carb with the new B&S OEM and made sure that the governor was set properly. I started it and let it warm up. The surging problem is gone . When I lowered my throttle to minimum setting it died so I got my tachometer and adjusted my idle speed screw to 1750 RPM. The tachometer shows that it is running about 3100 RPM at max throttle. Correct me if I am wrong, that RPM is controlled/adjusted by the tension of the spring on the governor. I could bend the tab to change that, correct?
My main question is about adjusting the fuel/air mixture jet setting. I have been unable to find that proceedure anywhere. The engine origionally had a Walbro LMT carb I do believe as the service manual that I downloaded doesn't have the proceedure for a Nikki made carb. I am refering to B&S SM 270962 Single Cyl L-Head Sec03 Carburetion. I did find the LMT instructions on pages 47 & 48. Would this same proceedure work for the Nikki?

Those instructions have been reliable for many years and are just a basic guideline for a set point before stating the engine and warming up. Once running minor adjustments may be needed. Listen carefully how the engine responds to these adjustments. The goal is to adjust until you get the smoothest running and best power.

I set main fuel mixture needle adjustment first at high RPM and then the idle mixture at idle accordingly.

No two engines have exactly the same adjustment settings and adjustments may need to be slightly changed from time to time.

The top governor speed is usually adjusted by bending the tab gently where the governor spring attached to the bracket. Do not exceed 3600 RPM. As for idle, it can be set where the engine sounds "comfortable" and not struggling to run.

"L" head engines rely on splash and slinger oiling, so the idle RPM cannot be too low. It is never a good idea to let these engines idle for extended periods anyway.

Thanks for the reply. Sounds like I'll need the neighbor to help when he has time to. He has lots of experience and would know how it needs to sound.

Auto Doc's said:

Those instructions have been reliable for many years and are just a basic guideline for a set point before stating the engine and warming up. Once running minor adjustments may be needed. Listen carefully how the engine responds to these adjustments. The goal is to adjust until you get the smoothest running and best power.

I set main fuel mixture needle adjustment first at high RPM and then the idle mixture at idle accordingly.

No two engines have exactly the same adjustment settings and adjustments may need to be slightly changed from time to time.

The top governor speed is usually adjusted by bending the tab gently where the governor spring attached to the bracket. Do not exceed 3600 RPM. As for idle, it can be set where the engine sounds "comfortable" and not struggling to run.

"L" head engines rely on splash and slinger oiling, so the idle RPM cannot be too low. It is never a good idea to let these engines idle for extended periods anyway.

Click to expand...

I have one engine that I just finnished a valve job on that's on a simple test stand with nothing on the shaft. I recieved the parts for rebuilding the Walbro carb on it and got all back together. It will start on first pull with the choke applied then opened for it to run smooth. Should it be on the mower with some load before setting the fuel mixture? That adjustment is a pain to get to installed on the Snapper RER; easy on the test stand obviously. But if it needs to be running with some load then I'll make it happen.

Get the best running conditions on the stand first.

It is a pain on this design, but the basic settings usually gets you very close.

The main needle is the only one adjusted when at hi idle and no load. Once under load and cutting the engine should respond properly.

Get the best running conditions on the stand first.

It is a pain on this design, but the basic settings usually gets you very close.

The main needle is the only one adjusted when at hi idle and no load. Once under load and cutting the engine should respond properly.

Get the best running conditions on the stand first.

It is a pain on this design, but the basic settings usually gets you very close.

The main needle is the only one adjusted when at hi idle and no load. Once under load and cutting the engine should respond properly.

Thanks to the stupidity and slow speed of this site, my reply load 3 duplicates

Auto Doc's said:

Get the best running conditions on the stand first.

It is a pain on this design, but the basic settings usually gets you very close.

The main needle is the only one adjusted when at hi idle and no load. Once under load and cutting the engine should respond properly.

Click to expand...

Thanks for another reply!
Yes, I turned a full turn both ways and couldn't hear any change. Another half turn CW would have been seated so I figured that the 1 and 1/2 CCW from seated was not lean. If the plug shows rich soon then I'll adjust.

Put a saved search on ebay for a Walbro LMT.
I keep one around just as a sub for the Nikki's.
Some of them China Clone Nikki's will never run right even when new. Lots of info on-line (you tube) about how to kit them. I buy the clones from Amazon on-line with free returns, sometimes have to get three or more to get a good one.
A Walbro LMT will eventually show up and they are easy to work on.
Make sure the plastic manifold is not leaking/cracked and I make a flat gasket for the manifold to head instead of relying on the o-ring for a good seal.

Briggs Nikki parts/pieces can be found here reasonably priced.

Forest#2 said:

Put a saved search on ebay for a Walbro LMT.
I keep one around just as a sub for the Nikki's.
Some of them China Clone Nikki's will never run right even when new. Lots of info on-line (you tube) about how to kit them. I buy the clones from Amazon on-line with free returns, sometimes have to get three or more to get a good one.
A Walbro LMT will eventually show up and they are easy to work on.
Make sure the plastic manifold is not leaking/cracked and I make a flat gasket for the manifold to head instead of relying on the o-ring for a good seal.

Briggs Nikki parts/pieces can be found here reasonably priced.

Search: 10 results found for "briggs stratton nikki"

Sawzilla Parts

sawzillaparts.com

Click to expand...

Thanks

Be aware if you try to look for a Walbro LMT using the Briggs part number for your engine's carb you will be directed to the Nikki replacement carbs, so when searching ebay you will probably have to search for a USED Walbro LMT carb. (and look for the name Walbro LMT on the side of the carb)

Here is a link that will show you how to clean and repair your carbs.