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

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WA Newbie & His Kid

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Hi All -- Glad to be part of the group. My 10 yr old son has a question. Thanks a million in advance for your help. He has a Husqvarna chain saw (a 55) that he changed the cylinder and piston on, and he just put in a new carb. Before he changed the carb, the chain saw would start up, run good for 2 seconds, and then would not rev up at all. So he replaced the carb, and now it runs good for about 2 and a half minutes, and then it won't rev up and it is dying on him again. He thinks maybe the new carb has to be adjusted or maybe the fuel line is sucking air, and then he's wondering if he did something wrong when he changed the cylinder and piston, causing it to lose compression? He's tried adjusting the carb and he thinks that it's making a small difference. He's also wondering if a sparkplug issue might cause this. It's a 1999. Does anyone have any advice for him? Thank you again.
 
Hi All -- Glad to be part of the group. My 10 yr old son has a question. Thanks a million in advance for your help. He has a Husqvarna chain saw (a 55) that he changed the cylinder and piston on, and he just put in a new carb. Before he changed the carb, the chain saw would start up, run good for 2 seconds, and then would not rev up at all. So he replaced the carb, and now it runs good for about 2 and a half minutes, and then it won't rev up and it is dying on him again. He thinks maybe the new carb has to be adjusted or maybe the fuel line is sucking air, and then he's wondering if he did something wrong when he changed the cylinder and piston, causing it to lose compression? He's tried adjusting the carb and he thinks that it's making a small difference. He's also wondering if a sparkplug issue might cause this. It's a 1999. Does anyone have any advice for him? Thank you again.
He’s 10?!?!:surprised3: He’s above my pay grade already.
 
When you say it runs 2.5 minutes is that at idle or during use? Does it start normally after sitting a while?
One thing about a 10 yr old's sense of time is that it's different (I forgot, sorry). So here's a correction. I checked: it's more like he can get it to go for about a minute or so of idling and good revving, and then it doesn't run right, it won't rev up, sometimes it just dies. Yes, it does start normally after sitting a while. Thanks!
 
Recommend you get him a carb kit for the original carb. If he purchased a chinese replacement it may never run good again. If he's talented enough to swap out a P&C, get him to watch a couple you tubies on rebuilding chainsaw carbs and for a few dollars he'll be a lot further along than swapping to a junk carb. Besides, better for him to clean up the old one.
 
Thank you all. You got me a little worried, Rick. He got the carb kit called: Carburetor For Husqvarna 55 51 50 Chainsaw 503281504 Walbro WT-170-1 Fuel line, on eBay, sold by playhome7. It had 4 good product reviews (4 or 5 stars) and the seller's positive rating is over 99%, but... I sure hope it didn't ruin the saw. Are you saying you have to get an OEM carb or else? We'll try the plug (been wondering about that, but if it runs good for a whole minute plus...). We'll try the breather/suction, and tuning the carb (he's been trying to -- any specific ideas on this?). He's learned a ton from YouTube. Most of what he knows about all this stuff is from YouTube. So we'll look at some vids on rebuilding chainsaw carbs -- great idea. Another friend recommended changing out the fuel line. Sounds like a good idea, too. He really really appreciates everyone's help. Tough to watch a kid go through this, but if he gets it working it'll be that much better a lesson. Thanks again to everyone.
 
I agree with Skv. Stopping after 2 1/2 mins shows that its running and likely just a vacuum is being created in the fuel tank restricting fuel flow. You could try timing it? Open fuel cap to release vacuum, put cap back on, start it and leave it on low idle and time until it cuts out. Then take off the fuel cap completely and put it back on (releasing the vacuum) and then do it WOT in a log and see if it cuts out much quicker the second time? Or just clean / replace the fuel tank vent valve / breather hehe.
 
There is always the possibility that a replacement part is faulty, even oem but more so with AM parts. The new carb, if faulty, shouldn't cause any damage other than a headache.

Most find it a good idea to change the fuel line, fuel filter, and plug (& maybe impulse line) from the start. It sounds more like a fuel delivery problem, but coils fail as they get hot when going out.
 
Thank you all. You got me a little worried, Rick. He got the carb kit called: Carburetor For Husqvarna 55 51 50 Chainsaw 503281504 Walbro WT-170-1 Fuel line, on eBay, sold by playhome7. It had 4 good product reviews (4 or 5 stars) and the seller's positive rating is over 99%, but... I sure hope it didn't ruin the saw. Are you saying you have to get an OEM carb or else? We'll try the plug (been wondering about that, but if it runs good for a whole minute plus...). We'll try the breather/suction, and tuning the carb (he's been trying to -- any specific ideas on this?). He's learned a ton from YouTube. Most of what he knows about all this stuff is from YouTube. So we'll look at some vids on rebuilding chainsaw carbs -- great idea. Another friend recommended changing out the fuel line. Sounds like a good idea, too. He really really appreciates everyone's help. Tough to watch a kid go through this, but if he gets it working it'll be that much better a lesson. Thanks again to everyone.
I wouldn’t be too worried about AM carbs. Most work.
 
Thank you all. You got me a little worried, Rick. He got the carb kit called: Carburetor For Husqvarna 55 51 50 Chainsaw 503281504 Walbro WT-170-1 Fuel line, on eBay, sold by playhome7. It had 4 good product reviews (4 or 5 stars) and the seller's positive rating is over 99%, but... I sure hope it didn't ruin the saw. Are you saying you have to get an OEM carb or else? We'll try the plug (been wondering about that, but if it runs good for a whole minute plus...). We'll try the breather/suction, and tuning the carb (he's been trying to -- any specific ideas on this?). He's learned a ton from YouTube. Most of what he knows about all this stuff is from YouTube. So we'll look at some vids on rebuilding chainsaw carbs -- great idea. Another friend recommended changing out the fuel line. Sounds like a good idea, too. He really really appreciates everyone's help. Tough to watch a kid go through this, but if he gets it working it'll be that much better a lesson. Thanks again to everyone.
I don’t know if you have the ability to take a video of it running with your phone and post it up we can help diagnose better as well. YouTube offers free uploads and you can link it here.

I really commend you and your son for working through this. My dad wasn’t mechanically inclined so I had a slow, rough road to learning engine repair.
 
Hi All -- Glad to be part of the group. My 10 yr old son has a question. Thanks a million in advance for your help. He has a Husqvarna chain saw (a 55) that he changed the cylinder and piston on, and he just put in a new carb. Before he changed the carb, the chain saw would start up, run good for 2 seconds, and then would not rev up at all. So he replaced the carb, and now it runs good for about 2 and a half minutes, and then it won't rev up and it is dying on him again. He thinks maybe the new carb has to be adjusted or maybe the fuel line is sucking air, and then he's wondering if he did something wrong when he changed the cylinder and piston, causing it to lose compression? He's tried adjusting the carb and he thinks that it's making a small difference. He's also wondering if a sparkplug issue might cause this. It's a 1999. Does anyone have any advice for him? Thank you again.
Check all simple items first, pinched fuel line, bad fuel line, fuel tank vent, fuel filter new, plugged muffler screen.
 
Fuel breather might be plugged.

Immediately after it dies, open the fuel cap and see if there’s suction.

Immediately after it dies, open that fuel cap just a bit, close it, and then try to restart. You may, or may not, hear any suction being released when the fuel cap is opened. If that solves it, it's a plugged fuel tank vent as mentioned above.

Also, if that fuel line is at all "squishy" it might be collapsing as the saw tries to draw fuel. Symptom would be that the saw starves for fuel until it dies - sounds like what you have going on to me. If true, replace the fuel line.
 

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