Husqvarna 51 stalls when warm

[Matt D]

My recently acquired Husqvarna 51 is giving me some trouble. The saw fires right up cold and idles nice but once I put it into some wood and make a couple cuts it will stall when I let off the throttle. The only way I can start it is by holding the throttle open while pulling the rope and unless I stay on the throttle it will die. I checked the spark plug and it looks fine, I also did a compression test with the motor cold and it reads 145psi on my tester. I thought I had the problem licked when I found the fuel line cracked where it exits the thank and goes into the carb, but I replaced the line and the fuel filter and the issue is still there. I fiddled with the H/L screws and the issue didn't go away. My next thought is to throw a carb kit at it but I hate to just throw parts at stuff. I'm pretty mechanically inclined and can troubleshoot snowmobiles and automobiles all day long but these 2 stroke saws seem way to temperamental. Any thoughts on how to diagnose this thing? I have access to about every tool except a pressure/vacuum tester.

Thanks!
Matt

 

[Stump Shot]

Either your tank vent is not working or it's developing a leak somewhere when warmed up most likely. Unfortunately the one tool you don't have is the very one you need to help diagnose your problem. If you're into DIY 2 stroke repair it might be a good investment for you to make. Other wise you will have to try and fix every possibility until you happen upon the right one.

 

[Matt D]

Either your tank vent is not working or it's developing a leak somewhere when warmed up most likely. Unfortunately the one tool you don't have is the very one you need to help diagnose your problem. If you're into DIY 2 stroke repair it might be a good investment for you to make. Other wise you will have to try and fix every possibility until you happen upon the right one.

The pressure/vacuum tester? I thought that was more or less to test for air leaks how would I test the tank vent with it? I may just have to buy one like you said it's a good investment for DIY repairs.

 

[Stump Shot]

The pressure/vacuum tester? I thought that was more or less to test for air leaks how would I test the tank vent with it? I may just have to buy one like you said it's a good investment for DIY repairs.

Drain fuel and pull off carb line at carb and pull a vacuum on it and see if it falls off or not.

 

[Matt D]

Just ordered the Mityvac MITMV8500 Silverline Elite Kit and a Fuel tank vent, the way I look at it is it's cheaper than shop time at this point and I'll have the tool for life.

 

[Matt D]

So my tester came today and I tested the fuel vent. Per the Husqvarna manual you are supposed to pressurize the tank to 7.2psi and it's supposed to drop off 3psi within 60 seconds. At first I couldn't get it to build pressure but soapy water revealed the fuel cap o ring to be bad. Swapped in a new o-ring and was able to get it up to 7psi and it dropped off 3psi within 60 seconds. Put it all back together fired it up and blipped the throttle to get it off fast idle and let it sit there idling and within 30-45 seconds it quit running. Pulled it over and it started for a second and stalled, pulled it over again and it started and I held down the throttle for 30 seconds and it stayed running but as soon as I let off the throttle it died and wouldn't restart without throttle. Being that the fuel tank vent checks out per Husky shop manual, what's my next move? Seems to me I have a fuel starvation on the low(idle) circuit, carb cleaning/rebuild kit?

 

[Stump Shot]

A very likely suspect. You can also use your new tool to pressure check carburetors as well. You can do now to check for problems, always a good idea after a rebuild. Your Husqvarna manual should show the procedure.

 

[old guy]

My little 335xpt has been acting like that, I finally tore it down to find the impulse line broke, don't know how it ran at all.

 

[Matt D]

*Saturday morning update*

Pulled the carb from the saw dunked it in some fuel and pressure tested it. It held 7psi without dropping off. While digging around my parts pile I found an aftermarket carb rebuild kit and decided to rebuilt the carb for the heck of it. Well after getting it back together and getting the carb dialed in it's running real strong and hasn't died yet. Going to sharpen the chain and makes some cuts with it tomorrow to make sure it's good to go but I think I've got the problem licked, thanks for the suggestions everyone!