10 yr old working on Husqvarna 55 saw (chain removed) -- has question

[buzz sawyer]

The chain is off the saw

That's why I said "once you get a chain on it".

 

[lostone]

What has he done with the tank vent? If the saw is starting fine and then going lean and dying, you said he can open the cap and relieve the vacuum and it starts fairly easy then does the same thing. Tank vent needs replaced.

I would stop running the saw over and over again until you replace the vent, it's just running the saw lean.

 

[lostone]

By the way he can remove the old one with a wood screw or drywall screw and a pair of pliers.

Just barely put the screw in far enough to grab the old one, grab the screw with side cuts or pliers and with a caming action it will come out fairly easy. Maybe find a video on it.

 

[Westboastfaller]

The next step is still raising the throttle and setting low jet properly. A vent usually takes a while for it to act up and will scream at a uncontrollable high rev and then cough out unless you open the gas cap. It's unmistakable. Your revs are too low not too high.

 

[John Stryker]

The saw looks in very nice shape, and well worth all the effort. Your boy has a lot of determination.
I think it is starving for fuel. in the video it runs fine till 1:45, then at 2:35 starts to lean out more (rev higher by itself), and at 6:45 when he opens the fuel cap it starts and runs better but seems to be a bit flooded (sluggish throttle response). Then at 8:05 it is flooded and stalls out. I suggest when flooded, to run it at full throttle for a few seconds till it clears up the unburnt fuel pooling in the crankcase, if he can start it.
Some tank vents of that era were a long black tube with a little white pill shaped filter pressed into it, on the right side of the tank behind the handle. If that white pill is plugged you can pry it out with an exacto knife and releive the vacuum in the tank that way temporarily, till you can replace the vent. The vent, if it has a flat slot in it, can be removed with a flat screwdriver, unscrewing it like a screw, and sometimes, if necessary, pushing on the other end through the tank at the same time with a pencil or something.
I hope the fuel starving issue is because of a blocked vent, or a kinked fuel line, because otherwise it could be due to a crankcase air leak, which opens up a whole bunch of other possibilities, and diagnosing, using fancy tools like a pressure/vacuum tester.

 

[John Stryker]

The part # for the tank vent is: 501 87 31 01 , according to the IPL for the 55.

 

[lostone]

The next step is still raising the throttle and setting low jet properly. A vent usually takes a while for it to act up and will scream at a uncontrollable high rev and then cough out unless you open the gas cap. It's unmistakable. Your revs are too low not too high.

I had a saw do the exact same thing his is and in my case it was a tank vent, opening the fuel cap and relieving the vacuum cleared it up. Mine would run about 1 1/2 to 3 min and die. Without a vacuum pump there is no way to prove this is or isn't his problem, however once the cap is opened on his it allows the saw to run which points to a vent in my opinion. If the vent is not working correctly there is no way the saw can be properly adjusted since it will not come up to temp to allow time for a proper settings.

Trying to diagnose something over the internet is almost impossible BUT everything leads towards a tank vent. There could be other factors at play here as well and this is why a pressure/vacuum pump is an invaluable tool when diagnosing these things to prove what the actual problem is.

 

[WA Newbie & His Kid]

We just read through all of your good comments. Together. He says "thank you". And that he really wants to try to replace the fuel tank vent, because he thinks that is definitely the problem. There is this other thing that happened after the 8 min video that we posted -- it started doing other things. So we will post another video soon. But this is really really helpful. Do you think that running it and testing it a lot in this condition has hurt the saw? (He is asking). Really can't thank y'all enough.

 

[svk]

I wouldn’t continue to run it until you fix the issue but you should be fine at this point.

 

[lostone]

Do you think that running it and testing it a lot in this condition has hurt the saw? (He is asking). Really can't thank y'all enough.

Probably not, however there is an easy way to tell. Pull the muffler and look at the piston through the exhaust port. There are plenty of examples of a scored piston on here to find as well as pistons that are fine looking at them through the port.

However if you know there is an issue and you believe you have it figured out there is no sense to continue running it and taking a chance. That is a very clean looking 55 and I would really like to see it get fixed. Finding one in that condition is hard to do.

 

[buzz sawyer]

I wouldn't run it until you know there is no lean issue. Too much good work done at this point to mess it up.

 

[WA Newbie & His Kid]

Hi Guys - been too long. He's been busy. And my theory is he's reluctant to mess with the fuel tank vent. If we can get it out, can we unclog it or should we get a new one? We made one more short video of the saw. He's pictured in this one a little. Next up: try to get the fuel tank vent out (couldn't find a video on that), see if we can clean it out somehow -- and if we can't, buy a new one, stick it in there and hope that fixes it. My theory is he's reluctant to go thru all that just to be disappointed again. Any more details anyone has on getting that vent out and cleaning it would be really appreciated. Thank you all very much again for all your generous advice. Here's the link to the new video. It's only a minute 45.

 

[husqORbust]

Surely the tank vent can be diagnosed before replacing it on a whim.
After 1.45 of running it like that, remove the fuel cap. Is the tank in vacuum?
Start the saw and lay it on its side, crack the tank cap. See if it runs better.

If not in vaccum or no change running on its side w/ tank cracked I'd rule out the breather.

I think the idle is set too low, the low jet isnt set right, or the compression is too low to idle.

What happens when if he just holds the throttle at a steady RPM?

I would:
Turn the idle screw in 1 full turn and see what happens. If nothing, turn it in 1 more turn.... can turn it in with the saw running while working the throttle to see if it brings idle up enough to idle by itself.

If that doesnt work. I'd leave the idle screw pinned and back out the low speed half a turn and note the change before deciding on what to do with the carb settings or where to go from there.

But lets back up a sec here... currently, where are the low and high needles set to from seated? Thats a huge indicator on where to go with the carb also, and tells if the carb settings are causing this issue in the first place.

The problem I see with running the saw without a chain is you cannot accurately tell where the Low speed and Idle is set. At minimum take the side cover off to see the clutch and use the brake to get the drum to stop spinning.

 

[WA Newbie & His Kid]

Surely the tank vent can be diagnosed before replacing it on a whim.
After 1.45 of running it like that, remove the fuel cap. Is the tank in vacuum?
Start the saw and lay it on its side, crack the tank cap. See if it runs better.

If not in vaccum or no change running on its side w/ tank cracked I'd rule out the breather.

I think the idle is set too low, the low jet isnt set right, or the compression is too low to idle.

What happens when if he just holds the throttle at a steady RPM?

I would:
Turn the idle screw in 1 full turn and see what happens. If nothing, turn it in 1 more turn.... can turn it in with the saw running while working the throttle to see if it brings idle up enough to idle by itself.

If that doesnt work. I'd leave the idle screw pinned and back out the low speed half a turn and note the change before deciding on what to do with the carb settings or where to go from there.

But lets back up a sec here... currently, where are the low and high needles set to from seated? Thats a huge indicator on where to go with the carb also, and tells if the carb settings are causing this issue in the first place.

The problem I see with running the saw without a chain is you cannot accurately tell where the Low speed and Idle is set. At minimum take the side cover off to see the clutch and use the brake to get the drum to stop spinning.

Hi All --

It has been a long time since we posted. Here is an update.

We never did get it to work right, so we finally wound up taking it to a local logging supply store to be diagnosed. Here is what their repairman found and did (I am cutting and pasting off of the receipt, sorry about all the Caps):

CUSTOMER INSTALLED NEW PISTON/CYLINDER AND CARB PLEASE CHECK OPS SAID ITS LEANING OUT TOP END

Order Note: SEALED IMPULSE HOSE , MANIFOLD TUBE, TORQUED CYLINDER, VAC-PRESS TESTED, CARB & CYLINDER CHINESE KNOCK OFF PARTS , MADE RUN NO WARRANTY.

So that's what he did (without telling us, unfortunately). He also said he adjusted the carb. We just wanted it diagnosed. The cylinder hadn't been torqued down all the way (because we didn't have a torque wrench). They were adamant about Chinese parts, but we think the parts are OK. They did do the vacuum-pressure test.

The problem is: my son found that it's worse now than when we gave it to them. It runs for less time. It barely runs. I can't think of anything that could have happened after we picked it up, except it was in the trunk of my car and not secured, so it moved a little, not a lot.

We're kinda at a loss. Does anyone have any ideas? Could we create a Christmas miracle for my kid? He's down about it.

As always, thank you all very much for your help. We look forward to your insights.

 

[buzz sawyer]

Sometimes you have to do things in order to diagnose and there should be a charge but he should have told you exactly what he found wrong. Vac/pressure test first and then tell you there are leaks and cost to repair. That being said, from earlier videos, I didn't see anything that would lead me to believe what he did would correct the problem.

I've used a number of Chinese carbs with no problems but it could still be bad. Tell your son not to be down about it. He's done a lot of good work. We all get that one saw that doesn't behave. Sleep on it and keep trying. I've had some elusive problems with cars and actually dreamed of the solution - and fixed it the next day. Since IMO, the only thing the guy did that would make a change is adjust the carb, I'd see how far the mixture screws are out and reset to where you had them. If that improves it, I would think there may be a carb problem.

 

[John Stryker]

Hi All --

It has been a long time since we posted. Here is an update.

We never did get it to work right, so we finally wound up taking it to a local logging supply store to be diagnosed. Here is what their repairman found and did (I am cutting and pasting off of the receipt, sorry about all the Caps):

CUSTOMER INSTALLED NEW PISTON/CYLINDER AND CARB PLEASE CHECK OPS SAID ITS LEANING OUT TOP END

Order Note: SEALED IMPULSE HOSE , MANIFOLD TUBE, TORQUED CYLINDER, VAC-PRESS TESTED, CARB & CYLINDER CHINESE KNOCK OFF PARTS , MADE RUN NO WARRANTY.

So that's what he did (without telling us, unfortunately). He also said he adjusted the carb. We just wanted it diagnosed. The cylinder hadn't been torqued down all the way (because we didn't have a torque wrench). They were adamant about Chinese parts, but we think the parts are OK. They did do the vacuum-pressure test.

The problem is: my son found that it's worse now than when we gave it to them. It runs for less time. It barely runs. I can't think of anything that could have happened after we picked it up, except it was in the trunk of my car and not secured, so it moved a little, not a lot.

We're kinda at a loss. Does anyone have any ideas? Could we create a Christmas miracle for my kid? He's down about it.

As always, thank you all very much for your help. We look forward to your insights.

The saw shop's order note does not mention doing a vacuum test on the tank to check the tank vent. Also they didn't say if the saw passed the pressure/vacuum test, but I am guessing it did.
As many have already suggested, a quick test is to loosen the gas cap while on it's side so the gas doesn't spill out. Another thing you can check is that the fuel filter is sitting on the bottom of the tank and not sucking air.
Just some ideas.

 

[WA Newbie & His Kid]

Thanks! Will pass this along.

Sometimes you have to do things in order to diagnose and there should be a charge but he should have told you exactly what he found wrong. Vac/pressure test first and then tell you there are leaks and cost to repair. That being said, from earlier videos, I didn't see anything that would lead me to believe what he did would correct the problem.

I've used a number of Chinese carbs with no problems but it could still be bad. Tell your son not to be down about it. He's done a lot of good work. We all get that one saw that doesn't behave. Sleep on it and keep trying. I've had some elusive problems with cars and actually dreamed of the solution - and fixed it the next day. Since IMO, the only thing the guy did that would make a change is adjust the carb, I'd see how far the mixture screws are out and reset to where you had them. If that improves it, I would think there may be a carb problem.

 

[WA Newbie & His Kid]

The saw shop's order note does not mention doing a vacuum test on the tank to check the tank vent. Also they didn't say if the saw passed the pressure/vacuum test, but I am guessing it did.
As many have already suggested, a quick test is to loosen the gas cap while on it's side so the gas doesn't spill out. Another thing you can check is that the fuel filter is sitting on the bottom of the tank and not sucking air.
Just some ideas.

Thanks! Will pass this along, too. There's always hope.