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B&S 5hp is driving me nuts

#1

C

Chillywilly

Hi, this is a helmet scratcher....starts good, runs good both at fast and slow idle. After cutting grass for a while the engine starts surging with even just a bit of load, then surging gets worse even at standstill. I have to keep it running by continually pressing the primer bulb. It's like when the engine gets hot it bogs down. But this is at fast idle, at slow idle the engine runs fine. Here is recap of what I have done so far; newer fuel and air filter, newer plug, cleaned fuel bowl, new fuel. I also replaced the drive belt but that shouldn't play into this. What am I missing or what to do next. Appreciate the insight. B&S 5 hp 4 stroke. Thanks


#2

ThaxtexGM

ThaxtexGM

Chillywilly said:
Hi, this is a helmet scratcher....starts good, runs good both at fast and slow idle. After cutting grass for a while the engine starts surging with even just a bit of load, then surging gets worse even at standstill. I have to keep it running by continually pressing the primer bulb. It's like when the engine gets hot it bogs down. But this is at fast idle, at slow idle the engine runs fine. Here is recap of what I have done so far; newer fuel and air filter, newer plug, cleaned fuel bowl, new fuel. I also replaced the drive belt but that shouldn't play into this. What am I missing or what to do next. Appreciate the insight. B&S 5 hp 4 stroke. Thanks
Click to expand...
Sounds like the main jet is blocked..


#3

reynoldston

reynoldston

Give the carburetor a good cleaning. Engine surging is low speed circuit in the carburetor.


#4

C

Chillywilly

Thanks, do I need to remove the carb to do that or can I simply spray it down with c cleaner. interesting that the fuel bowl was clean or is that not unusual.


#5

reynoldston

reynoldston

Chillywilly said:
Thanks, do I need to remove the carb to do that or can I simply spray it down with c cleaner. interesting that the fuel bowl was clean or is that not unusual.
Click to expand...

Yes you will need to remove the carburetor. Buy yourself a repair kit and disassemble the carburetor and give it a very good cleaning inside and out. Just what do you mean by fuel bowl because dirt will collect in the bottom of it as a rule.


#6

C

Chillywilly

The bowl at the bottom of the carb unit, has a screw at the bottom which holds it in place, in that screw are ports and all were clean. Thanks


#7

reynoldston

reynoldston

Chillywilly said:
The bowl at the bottom of the carb unit, has a screw at the bottom which holds it in place, in that screw are ports and all were clean. Thanks
Click to expand...

I believe you are talking about the high speed circuit, now for engine surging it would be more into the low speed circuit. As I said in my first post. This is the reason you will need to remove and completely disassemble the carburetor.


#8

C

Chillywilly

Good advice...so just for the heck of it, started the mower this am., ran without issues for about 10 minutes, then the engine started struggling both at standstill and fast/full throttle. Again had to keep it alive by pushing primer bulb. What's interesting is that at low throttle it runs without primer aid, albeit the idle is tough. Lots of fun...


#9

reynoldston

reynoldston

Chillywilly said:
Good advice...so just for the heck of it, started the mower this am., ran without issues for about 10 minutes, then the engine started struggling both at standstill and fast/full throttle. Again had to keep it alive by pushing primer bulb. What's interesting is that at low throttle it runs without primer aid, albeit the idle is tough. Lots of fun...
Click to expand...

From the sounds of it the sounds like it is starving for fuel. No Vacuum leaks? Are you getting a very good flow of fuel to the carburetor. You did change the fuel filter but could the fuel line be plugged or bad? Fuel tank vented and nothing blocking the fuel outlet inside the fuel tank? You might also check your exhaust system and make sure nothing is plugged there like a bad muffler? Only guessing.


#10

C

Chillywilly

Re: B&S 5hp is driving me nuts - more

So I sprayed carb cleaner into the carb and cleaned up any visible dirt. Significant improvement to where I continue to have to press the bulb to keep it running, for about 5 minutes and then she runs at WOT without issue. To summarize, cold start is fine but won't run without priming with bulb, then when engine gets to operating temp it will run unaided. Any additional suggestions welcome, as always thanks in advance.


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