Briggs 17.5 HP with Nikki Carburetor Surging only when cold . (Craftsman Lt1500)

mstar

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  • / Briggs 17.5 HP with Nikki Carburetor Surging only when cold . (Craftsman Lt1500)
Hi
I have a bought a used LT1500 mower with Briggs and Stratton engine 31C707 3346 G6 engine Code 110510ZD It has a Nikki Carburetor

It starts right up but surges for a minute or so before it warms up. Then it seems to run fine. Maybe a surge when the PTO is first engaged but I have not used it more than a test.

I did the basics to start fresh with the machine, New : spark plug, fuel filter, oil change, air filter. I also changed the gas. I also tried this with the gas cap and air filter off and it did not change the surging.

It had always been garaged and I am assuming in winter was stored with gas in. So I could see how the carb could have blockage and need a break down and clean. I have not done this but seen quite a few videos are posted about this carburetor and it looks easy enough.

1. if it is only running this way at start up , is it the carb or could it just be an adjustment?
2. If just an adjustment, how should I proceed to give a tune up ? the carb?

I have read some say they either did a clean or even replaced the carb and it still surged after. I never saw them post if they found the cause.

I also see allot of kits on amazon and ebay cheap but mixed reviews. It concerns me I do a rebuild and it does not fix if that is not the issues

So i am asking for help as this could just be an adjustment for cold start and I donot need a clean. I don't understand enough about how they work to know what would only cause the surge at cold start.

And when I say cold.... I mean it is NOT cold. It was High 60s and if I turn off for 10 minutes after it smoothed out. It starts to surges again but not as hard and smooths out quicker When it is cold it surges harder at first and as things warm up it surges quieter and quieter and less frequent until it is running smooth.

3. Is there a good aftermarket kit? I don't want to over spend on a $55 briggs kit if many say it does not fix their surging and does concern me that some replaced the carb and it still did not fix.

4. it seemed the owner knew of this and just played with the choke until it cleared out. when I put the joke up the surge stops for a few seconds and then there is too much fuel so it starts to act up and he dropped it back to fast, the surge was start and he would move the choke back up and repeat . I guess he did this so he did not have to listen to the surge.
But this info might give an expert here an idea if it is more of an adjustment than something in the carb.

Thanks in advance for any advice.
So what do I do
 

Ronno6

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  • / Briggs 17.5 HP with Nikki Carburetor Surging only when cold . (Craftsman Lt1500)
At first glance it would appear that the engine is a bit cold-natured. (60° IS cold to an engine!)
This could be due to lean running conditions mandated by the EPA.
They are so concerned about emissions that some B&S/Nikki 2bbl carbs have different sized jets for each cyl!
Moderating the choke til it warms up a bit may be your best option.
It is a bit of a by-feel situation.
I personally would not consider it a big deal.

As for kits, I discussed the $$$ of B&S kits with an actual Briggs engineer.
He said that the high price is due to the expensive materials required to withstand
the ethanol in today's gasoline. We owe another big thank you to the EPA for that............

As for the cheaper kits, I have no experience with them. If you opt for one, I hope you are burning
non-ethanol gas in your mowers.
I have used nothing but since relocating to south Mississippi and I have never experienced another fuel related problem,
carb or otherwise.
 
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  • / Briggs 17.5 HP with Nikki Carburetor Surging only when cold . (Craftsman Lt1500)
Actually to rekit your carb would cost about 6 bux. The noodle gasket and a welch plug. Briggs parts.

Clean real well in a dip or spray all the passages out well, let dry and repeat if you are using a spray. Take the welch plug out before you do that.

You can leave it like it is for a while and run it like it is. When it gets worse then redo the carb ~!~!
 

mstar

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  • / Briggs 17.5 HP with Nikki Carburetor Surging only when cold . (Craftsman Lt1500)
Actually to rekit your carb would cost about 6 bux. The noodle gasket and a welch plug. Briggs parts.

Clean real well in a dip or spray all the passages out well, let dry and repeat if you are using a spray. Take the welch plug out before you do that.

You can leave it like it is for a while and run it like it is. When it gets worse then redo the carb ~!~!

Well to wait is a thought. It was just that i thought under a little load when I was testing it it might have started to stall but then caught up.

Can you clarify? What is $6? Are you saying get an $6 after market kit and then by the other two pieces mentioned from Briggs?
What about the needle? Shouldn't the needle and seat be changed while I have it all apart?

If I lightly push on the choke, this surging can be reduced or eliminated. Is it then an adjustment or need of clean?
 
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  • / Briggs 17.5 HP with Nikki Carburetor Surging only when cold . (Craftsman Lt1500)
No it's 6 bux or so for the bowl gasket and a welch plug. We call them noddle gaskets down here.

needles are very expensive for that carb. They last a very long time though. You have to take the carb off to do it right because of the way the gasket sets in there.
 

ILENGINE

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  • / Briggs 17.5 HP with Nikki Carburetor Surging only when cold . (Craftsman Lt1500)
With the new emissions engines, I have brand new out of the box engines run like crap, meaning surging, backfiring until they warm up in the middle of the summer So what you are experiencing may be normal for that engine.
 

mstar

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  • / Briggs 17.5 HP with Nikki Carburetor Surging only when cold . (Craftsman Lt1500)
Thanks. The link was helpful . I might have missed some spots.
 

mstar

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  • / Briggs 17.5 HP with Nikki Carburetor Surging only when cold . (Craftsman Lt1500)
So I will be using this when it is colder than 60F so don't want an issue. However, I also don't want to waste time and money if this is just the way they all work in this model.

With the new emissions engines, I have brand new out of the box engines run like crap, meaning surging, backfiring until they warm up in the middle of the summer So what you are experiencing may be normal for that engine.
 

ILENGINE

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  • / Briggs 17.5 HP with Nikki Carburetor Surging only when cold . (Craftsman Lt1500)
If it runs fine after a couple minutes or so, I wouldn't overthink it.
 
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