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

[mstar]

A little more testing,

From 4 gear up if I let my foot of the clutch, when it catches there is a power drop or surge for a second and then recovers. This causes a little buck. Does this symptom provide any other information if there is an adjustment that can be performed or if it needs to be cleaned?

 

[ILENGINE]

Sounds like there may be an issue with the transfer ports. When you go from no load to load there are holes or slots that allow the engine to transfer from the idle circuit of the carb to the main jet. So your carb may benefit from some cleaning. it will look like a series of small holes, or a slot behind the hole for the needle valve in the venturi of the carb

 

[mstar]

So why hasn't any external adjustments been suggested?
On the cold start, if I push on the choke wire a little to open it more it does not surge. Does a 6 year old carb not need adjustments or is it that a 6 year old carb is probably blocked.?
It just seems like the suggestions jumped to a carb clean and nothing else could be the issue.

 

[Fragger]

Maybe it's just me but i have a B&S 12 hp that does that same thing i just let it warm up and use it:dance1:

 

[Ronno6]

So why hasn't any external adjustments been suggested?

I am not familiar with your carb, but most other current units which I have serviced have no external carb adjustments.....

Valve settings are a typical issue, but you seemed to focus on the carb from the onset.

 

[mstar]

Maybe it's just me but i have a B&S 12 hp that does that same thing i just let it warm up and use it:dance1:

Does yours also do it as you release the clutch, even after warm?

 

[mstar]

I am not familiar with your carb, but most other current units which I have serviced have no external carb adjustments.....

Valve settings are a typical issue, but you seemed to focus on the carb from the onset.

Valves are now set to specs. Still surges until warm up.

Now I am back to weighing if it is just normal or if the carburetor should be properly cleaned.


I learned I am a bit too short legged for this machine. Some of my power issues were from slightly lifting off the seat to do of the following. 1. pushing the brake all the way, 2. pushing the PTO all the way down. 3 pushing the any lever to its lowest point.

Honestly they made this machine for people with giraffe legs and monkey arms.
I did not think I was coming off the seat that much but looking how the switch is made and how tight the seat springs are, I am too far on the edge that my full weight is not on the seat so any bounce or left or lean forward can start that anti backfire to kick in and then when I return to the seat caused the engine to come back.

It was more my physical limits than a UNDER LOAD engine issue. So my height coupled with "safety" is to blame for much of what was seeing


So now the only issue seems to be the surging for up to 2 minutes when cold. and if I start after it stis for a few minutes, it will surge a little but takes less time to get back.


This is the part that puzzles me.

If the engine has been running for 20 minutes. Why would it still surge, breifly even after it is warm.
Is the fact it only needs to sit a short period and will still surge even if it had been running for 20 minutes on a 70F day a symptom. If it was a dirty carb why would it surge when cold but also when hot but also run fine after it runs a little with the choke up?

Thanks for any input

 

[Ronno6]

Honestly they made this machine for people with giraffe legs and monkey arms.

Thanks for any input

Careful,now...I resemble those remarks..............
My MTD 46 incher us way too small for me.........
After an hour on it, I almost need a crane to lift me off..........

 

[Bill95]

I hate those Nikki carbs, i just replaced one that was FUBAR, the local dealer suppliers wanted 160$ canadian for a new carb, got the part number and got it on Ebay for 40$, brand new and runs great...you could do that.

 

[Boudreaux In Eunice La.]

Valves are now set to specs. Still surges until warm up.

Now I am back to weighing if it is just normal or if the carburetor should be properly cleaned.


I learned I am a bit too short legged for this machine. Some of my power issues were from slightly lifting off the seat to do of the following. 1. pushing the brake all the way, 2. pushing the PTO all the way down. 3 pushing the any lever to its lowest point.

Honestly they made this machine for people with giraffe legs and monkey arms.
I did not think I was coming off the seat that much but looking how the switch is made and how tight the seat springs are, I am too far on the edge that my full weight is not on the seat so any bounce or left or lean forward can start that anti backfire to kick in and then when I return to the seat caused the engine to come back.

It was more my physical limits than a UNDER LOAD engine issue. So my height coupled with "safety" is to blame for much of what was seeing


So now the only issue seems to be the surging for up to 2 minutes when cold. and if I start after it stis for a few minutes, it will surge a little but takes less time to get back.


This is the part that puzzles me.

If the engine has been running for 20 minutes. Why would it still surge, breifly even after it is warm.
Is the fact it only needs to sit a short period and will still surge even if it had been running for 20 minutes on a 70F day a symptom. If it was a dirty carb why would it surge when cold but also when hot but also run fine after it runs a little with the choke up?

Thanks for any input

Did you take the welch plug out like I said in a earlier post ??

Did you make sure all the little holes are cleaned out like LIL Engine said ??

If you take the welch plug out and give the holes a good clean with a small wire and a good soaking it will solve your problems. I hope ~!~!

Send a pic of the carb on here ~!~!