Husqvarna saw has me stumped

[ktpnw]

Thanks in advance for any advice here - I have a Husqvarna 460 rancher that won't start. First of all, I know I could've easily gotten a working saw for what I've spent on parts here. But I like fixing things and keeping things out of the landfill (and honestly I didn't think i'd get in this deep when I started the project.

I got this saw very cheap in "used to run but sat a while" condition. Super dirty but otherwise complete. I have replaced what I feel like is every part, and it still won't work. Here's what I've replaced, all with OEM parts:

Cylinder and piston, and gaskets. The body of the saw is actually a 455 Rancher, I put on a 460 cylinder and piston. But from what I've read that shouldn't matter.
Carb
spark plug, air filter, fuel filter
Fuel Line
Crank seals
Compression release valve
Impulse line
Muffler (used OEM, not clogged)

The saw ran, briefly. I got like three or four cuts out of it. But now, after lots of pulling, the saw will fire for like a half second and then immediately die. It passes a cylinder pressure test easily (went from 0.8 to 0.75 Bar in 30 seconds, pressure or vacuum), has great compression.

I took the limiter caps off the new carb and set them to what I believe to be factory settings (1.5 turns out on Low, 2.5 turns out on high). I don't really know where to start the idle adjustment, but I've tried everything.

Any ideas? I really don't know where to go from here. Again, all OEM parts. I am fairly new to small two strokes but I am very mechanically inclined, former professional bicycle mechanic, have succesfully rebuilt motorcycle carbs, etc.

Again, thanks in advance for any advice.

 

[Huntaholic]

Sounds fire related to me. Id change the coil. HOPEFULLY you can come up with one off another saw just to test to see if that's the problem.

 

[cookies]

check the coil gap and stop switch/wiring

 

[Roanoker494]

Is your fuel tank clean inside? Just had an old Homelite do the same. Fuel filter was clogging up.

 

[user 122190]

Empty the tank, remove the plug, compressed air into the carb, while cranking the engine over a good number of times. Will it then pop and run again, even briefly. Sounds like the fuel air is to rich.

 

[SawTrash]

I am fairly new to small two strokes but I am very mechanically inclined, former professional bicycle mechanic, have succesfully rebuilt motorcycle carbs, etc.

Over half a century of fettling 2 and 4 stroke cars, motorcycles, mowers DID NOT prepare me for chainsaw carbies
No motorcycle carb was ever made to function in all orientations such as sideways and upside down. You must pay attention to the impulse feed system and take particular care setting up the metering lever system. Other pitfalls are kinks in the fuel hoses. Getting the spark timing right is another possible problem, loose or sheared flywheel keys, and a bad or poorly functioning coil can have you tearing out your hair.

Good luck.

 

[MacAttack]

It sounds to me like it's flooded. Many times when a saw refuses to restart after its been running, it's because there is excessive fuel in the crankcase.

 

[frank_]

diagnosis is the key to these 2 strokes, throwing parts at them usually ends up with a moneypit
i always wet the air filter with fuel first (assuming the plug is dry)
then i check for a spark
only then will you know where to pinpoint

 

[ktpnw]

Sounds fire related to me. Id change the coil. HOPEFULLY you can come up with one off another saw just to test to see if that's the problem.

Thanks. It seems to have great spark when I test it by grounding out. Is it possible to have a bad coil but still good spark?

 

[ktpnw]

Is your fuel tank clean inside? Just had an old Homelite do the same. Fuel filter was clogging up.

Thanks, it is a brand new fuel filter, only ran for like ten minutes, but I'll pull it off and see if that changes anything. Easy check.

 

[ktpnw]

Over half a century of fettling 2 and 4 stroke cars, motorcycles, mowers DID NOT prepare me for chainsaw carbies
No motorcycle carb was ever made to function in all orientations such as sideways and upside down. You must pay attention to the impulse feed system and take particular care setting up the metering lever system. Other pitfalls are kinks in the fuel hoses. Getting the spark timing right is another possible problem, loose or sheared flywheel keys, and a bad or poorly functioning coil can have you tearing out your hair.

Good luck.

Good call. Yeah I've quickly learned that chainsaws are a whole other ballgame haha. I have checked for fuel line kinks, replaced impulse line, flywheel key seems fine, coil is still a potential issue. Will have to figure out if I can find another to test with or have to bite the bullet on a new one.

 

[MacAttack]

How about the basics like what does the spark plug look like when it won't start? That should be the first thing to check. Is it wet with gas? Or dry?

 

[ktpnw]

It sounds to me like it's flooded. Many times when a saw refuses to restart after its been running, it's because there is excessive fuel in the crankcase.

I should have been more clear, it ran for like ten minutes a couple weeks ago, but now will not run. This is not an issue of "runs till warm, then won't restart", it won't start at all beyond a half second spurt anymore. That being said, totally possible it is flooding. The plug is sometimes wet after I pull and pull and pull for a while. Would that indicate a carb adjustment problem? Or bad ignition?

 

[ktpnw]

How about the basics like what does the spark plug look like when it won't start? That should be the first thing to check. Is it wet with gas? Or dry?

Yes, spark plug is sometimes wet with gas when it won't start. I realize this means either too much gas (adjusted rich), or not sparking/igniting. But it seems to have good spark, and the carb is adjusted to factory settings. So unsure what to do about this. I have tried adjusting it leaner too, didn't help.

 

[MacAttack]

Yes, spark plug is sometimes wet with gas when it won't start. I realize this means either too much gas (adjusted rich), or not sparking/igniting. But it seems to have good spark, and the carb is adjusted to factory settings. So unsure what to do about this. I have tried adjusting it leaner too, didn't help.

I think you're experiencing a badly flooded engine, I've had this happen many times. Essentially, there is so much fuel in the crankcase, it just can't even start. Even with a good hot spark, it will just drown it out.
Here are the steps I'd take. Pull the spark plug, hold the saw with the plug facing down, pull the recoil over quickly for a good 15-30 seconds and see if you get gas spattering out. Put the plug back in, no choke, hold the throttle wide open, and pull it over quickly. If it starts to pop and want to run, keep pulling it over holding the throttle open and see if it starts.
When I had a saw with the metering lever set too high, the only way I could get it to start and clean out was to fully close the high speed needle and pull it over with the throttle open. It would start until it ran out of fuel, but as soon as I opened the needle at all, it would just flood.

 

[ktpnw]

I think you're experiencing a badly flooded engine, I've had this happen many times. Essentially, there is so much fuel in the crankcase, it just can't even start. Even with a good hot spark, it will just drown it out.
Here are the steps I'd take. Pull the spark plug, hold the saw with the plug facing down, pull the recoil over quickly for a good 15-30 seconds and see if you get gas spattering out. Put the plug back in, no choke, hold the throttle wide open, and pull it over quickly. If it starts to pop and want to run, keep pulling it over holding the throttle open and see if it starts.
When I had a saw with the metering lever set too high, the only way I could get it to start and clean out was to fully close the high speed needle and pull it over with the throttle open. It would start until it ran out of fuel, but as soon as I opened the needle at all, it would just flood.

This is great info, thanks. I have pulled the plug and cranked it over and over (a couple minutes) as well as pulled a bunch with the throttle open, so I have at least attempted to make sure it isn't flooded. That being said, it is possible the metering lever is set too high. I'm not familiar with how to adjust that, but will do some research.

I haven't touched the high speed needle, because I was under the impression that didn't affect anything at startup/idle. Is that incorrect? If so, I will try screwing that in as well.

 

[a. palmer jr.]

Yeah, the high speed needle has a small part in the starting because you should be on high idle during starting. Turn both screws out to about 1 1/4 turns and see if it helps. Also you might try another plug even though the other one showed spark. I wouldn't mess with the inlet lever just yet because it's been my experience that new carbs usually have the lever set about right..

 

[ktpnw]

Yeah, the high speed needle has a small part in the starting because you should be on high idle during starting. Turn both screws out to about 1 1/4 turns and see if it helps. Also you might try another plug even though the other one showed spark. I wouldn't mess with the inlet lever just yet because it's been my experience that new carbs usually have the lever set about right..

Thanks. I've actually tried four different spark plugs so it's not that. But good to know that the high idle adjustment does affect starting, makes sense. I'll give that a try as well.

 

[L34]

Thanks. It seems to have great spark when I test it by grounding out. Is it possible to have a bad coil but still good spark?

Yes.
Double the plug gap and see how spark looks.
Takes a lot more to fire under compression than plug against cylinder.

 

[J D]

To add a couple of things...
It's quite possible your new filter is gunked up... if the tank was empty for a while, all the crusties & old gas residues can come loose inside the tank when you fill it with fuel. I'd dump the gas into a clean container & inspect.
A plug may spark well outside the cylinder but struggle under compression... Doubling the gap outside the cylinder should confirm all is well.
Coils quite often start to play up or fail as they warm up (although this isn't your issue)
Carb would typically be set between 1 & 1¼ turns out on both L & H
What is your start up procedure?
Should be prime (if fitted), choke out, pull till you get a little pop, choke in, pull till it starts (don't touch throttle throughout).
If there's a primer does it pump & fill as it should?