Help needed - Husqvarna 55

lostone

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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.
 

Kenskip1

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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.
 

pioneerguy600

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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

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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.
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.
 
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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.
 

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Stihl-Pioneer

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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?

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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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.
 
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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

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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.
Look on the bright side, the cord should pull easy!
 

Dennbb

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I've about run out of ideas as to how to get this Husky 55 running decently. It will start and run for a few seconds, then die spontaneously or as soon as any throttle is applied. When first started, it will run a few seconds longer than subsequent restarts.
See it in action:


First, some background - saw has been worked on before by someone else.
Compression is only around 125 but that should be enough to run.
No scoring on piston, top end looks pretty new and I suspect it's after market.
I've done pressure/vacuum tests - no issues.
Second, what I've done (besides above):
New fuel filter although old one seemed good. Fuel line is flexible with no leaks (pressure tested).
Tried new carb (AM) with no change in behavior.
Put in new spark plug. Has strong blue spark - jumped 1/4" gap.
Replaced decomp with plug to rule out any leaks there.
Have tried all sorts of different carb settings starting from 1.25 turns out on both needles.
Set the gap on coil - it was much tighter than a business card.
There is minor scoring on the FW that suggests it rubbed on coil at some point.
FW key is intact and properly seated.
Any suggestions will be appreciated.

Compression is too low.
 
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.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.
 

Kenskip1

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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
 
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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.
 

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