Disconnect the fuel line at carb and run a Vac test on the fuel tank. If it holds vac the valve is bad, I had a Stihl 046 drive me insane trying to find out why it was doing the same thing. Not saying this is the problem you are having but if the valve is bad it won't allow fuel to get to the carb and you run lean. In your case you have a pressure/vac tester but if you don't an easy way to find out is start the saw and turn it on it's side like you are filling the tank and loosen the fuel cap (doing this with a half a tank of fuel) and if the saw continues to run then tighten the fuel cap and see if it dies.
Help needed - Husqvarna 55
- Thread starter atpchas
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Some of these replies are spectacular. I will say that the metering diaphragm is not pulsing down to push the metering needle down far enough to allow an adequate fuel supply to enter the carburetor. He has spark, so we can cross this off the list.
No you cannot, I have seen many of these start and run erratically for a few seconds then stall, it was the module going South and I had a hard time believing it but after much putsing about I swapped in a good module and the saw was fixed. These modern modules are not like the coils of old that were points condenser fired, with those if one had spark they almost always ran fine. Just a couple months back a good friend putzed about for more than a month on his Jonsered 2065, had the same problem Charlie had and I wanted to change out his module, he`s so cheap he just couldn`t believe it would fix his saw. After weekend after weekend went by with the saw starting but refusing to rev up, stalling over n over he finally gave in, a new module now fires the saw and it runs like new again.
dsell
Addicted to ArboristSite
Yep, ignition modules are a pain. I had one on a 50 series that lowered the power. Some are so expensive or obsolete that the engine is trash. Just went through that on my Mantis tiller, had to change the block. Had a bad coil on my 575 that was very intermittent and expensive.
I will be giving the fuel line extra close attention. Thanks!
Well, I think I have it licked with no small part going to the helpful suggestions here. Whoever did the previous top end replacement left out the gasket, perhaps to increase the compression?*** In any event, that left the impulse port in the base of the cylinder flat against the deck of the crankcase. There was no air whatsoever moving through the impulse channel in the cylinder (confirmed with mouth suction and some hose). Luckily, my meager Husky box o' parts had a gasket for the 55. I put it in, reinstalled everything, and Merry Christmas to me - it started up and actually responded to the throttle. I'm not completely convinced it is fully operational but I'm reluctant to take the saw outside and piss rev it enough to be confident the problem is gone - don't want my neighbors to hate me.
Now for one more question. I've read of folks doing a gasket delete on these 55s with no mention of any mods to accommodate impulse. Is that possible? If so, what am I missing? The picture shows the impulse hole in the cylinder (out of focus in the foreground) and the deck in the back ground. If the cylinder base is flush to the deck, how does the pulse get to the carb?
Again, thanks to all who took the time to make suggestions. I may yet need them.
*** I'm almost afraid to check the compression now with the gasket in place. It was poor before, what'll it be now? OTOH, I'm told the owner is 82 years old and the easier it is to pull over, the happier his shoulders will be.
Now for one more question. I've read of folks doing a gasket delete on these 55s with no mention of any mods to accommodate impulse. Is that possible? If so, what am I missing? The picture shows the impulse hole in the cylinder (out of focus in the foreground) and the deck in the back ground. If the cylinder base is flush to the deck, how does the pulse get to the carb?
Again, thanks to all who took the time to make suggestions. I may yet need them.
*** I'm almost afraid to check the compression now with the gasket in place. It was poor before, what'll it be now? OTOH, I'm told the owner is 82 years old and the easier it is to pull over, the happier his shoulders will be.
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Without a gasket you have to make a small channel in the case to line up with the hole for the cylinder with a file or a dremel.
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Thanks for the clarification. I figured that was the case but saw no mention of such in the several Husky 55 gasket delete threads I read.
Make sure and check the squish. Shoot for .020 or greater.
I'm afraid .020" is purely aspirational. This is an AM cylinder and squish was around 0.050" before I put a gasket in. The owner of this saw is a cheapskate (evidence - AM parts, used motor oil for bar lube), so unless he makes noise about lack of power, I'm leaving well enough alone.
dsell
Addicted to ArboristSite
Look on the bright side, the cord should pull easy!
Dennbb
ArboristSite Member
Compression is too low.
No question it is low. Whether it is too low remains to be seen. No impulse to carb appears to be the major problem.
.050 squish will never perform like you want from, in my opinion.
Not my decision to make. If the owner isn't satisfied with the performance, he has to decide know how much he's willing to pay to make it satisfactory. I'm working on the saw third hand. A buddy offered to try to fix it for the owner - someone I've never met - and brought it to me because I had more time than he did to get it sorted. Buddy will deal with owner.
While on this topic, I have a small suggestion. If your saw has a impulse line, take a bit of grease and cover the opening. Then with the spark plug installed pull it over a few pulls. If the grease disappears then you will have a good supply of vacuum to the carburetor. Don't ask me how I know this. Ken
Yes, a quick and easy check, especially useful to remember if one does not have a p/v tester.
