husqvarna 460 dies if give it power. new carb = same.

[cordwood10]

Husqvarna 460 rancher, 5 years old. always ran solid.
Recently during a days normal use running well, mid use it suddenly died if you give it anything more than medium power.
It starts and idols fine.

I changed the spark plug, fuel filter, air filter = same.
Installed a new carb = running exactly the same problem.

Because it happened suddenly, I assumed clog which is why I threw in a new carb ($26 Chinese amazon carb) rather than try to adjust the old one.

The Amazon clone carb seem identical except the high and low adjustment tool is different, whatever this tool is I have to find.

Any suggestions what to try next? Should I check compression? try adjusting the carb?
I didn't take enough apart to see where the fuel lines go, so those are the original. but didn't see any evidence of gunked lines in the small clear lines on the old carb.

p.s. anyone know what this carb adjust tool is?

 

[Huntaholic]

Impulse line. That, or you've got a seal shot causing an air leak.

 

[cordwood10]

Thanks i just looked up impulse line on google (had never heard of it). Sounds very plausible, the line i think might be the impulse line was a very short hose coming out of the housing barely enough to slip it on to the carb w a needle nose.

Afte that i can't see where it went, unless i take more apart. Sounds like ill be taking it apart again tomorrow to take a look.

 

[Huntaholic]

Thanks i just looked up impulse line on google (had never heard of it). Sounds very plausible, the line i think might be the impulse line was a very short hose coming out of the housing barely enough to slip it on to the carb w a needle nose.

Afte that i can't see where it went, unless i take more apart. Sounds like ill be taking it apart again tomorrow to take a look.

It will go to the base of the cylinder or the top back of the crankcase. It basically serves as a fuel pump pulling fuel into the carb.

 

[cordwood10]

I have not taken more apart yet to see the remainder of the impulse line. The part i can see looks visually normal.

One thing i noticed... When you pump the primer bulb its limp with a mix of air and bubbles in the clear line leading to and from the carb (worse on the line connecting to the carb).
It sounds irregularity like air pumping.

The primer bulb never goes past half full and you can hear air escaping somewhere for a few seconds after you pump it.

I have a different smaller husqvarna saw as well. when you prime it the bulb fills and goes stiff.

am i right to assume there is definitely an air leak somewhere? Which could be the impulse line or seal mentioned earlier.

Could it be a bad primer bulb and could that cause air leak while running?

There are no liquid leaks detected.

 

[Jasent]

Sounds like a cracked fuel line to me. With bad impulse line you typically don’t get a good idle

 

[cordwood10]

I took another stab at it (im a carpenter not a mechanic)

The primer bulb wont stay firm and you can hear air pissing out slowly somewhere after priming.

Primer bulb pulls gas through the carb. If i block the other end of the bulb, it will pump up firm (bulb still only half full of gas)

...so the other end of the bulb, ive taken apart more but i cannot see where the end of that line is going. If there is a crack in that fuel line... It is past whatever housing i can get to without dismantling further.

Took a shot at more dismantling but i think i might throw in the towel and try a repair shop. I cant seem to gain access to the other end of that fuel line where it presumably feeds to the motor.

If its not that line would it be a blown seal? (not that i even know what that really means)

 

[Huntaholic]

Im not too familiar with the series youre working on but I THINK its a clamshell design crankcase. If so, and its not a fuel line or impulse line, I personally would scrap it. The seals I was talking about are the crankshaft seals and I personally wouldn't fool with rebuilding a clamshell case.

 

[smokey7]

Check the 4 screws are in and tight on the under side of the saw