Husquvarna Rancher 50 - Fires but doesn't keep running.............

[XPLRN]

Last year I got a really nice low usage white top Rancher 50. I'm finally getting around to finding out what the saw is all about as the original owner had told me that it had some kind of carb issue as it would fire but not run.

Recently I had two pieces of equipment that didn't want to start with the wet plug/wet cylinder syndrome. Tore them apart, found the hardened up metering diaphragms, replaced them and they ran just like they should. Figured since this Rancher 50 was known to have a carb issue I'd be able to easily get it up and running by doing the same thing..............not there yet.

The things I've done to this saw;

1. New fuel line(used the filter that was in it) and took the tank vent out to check it (seems to be clean)

2. Installed carb kit........however the diaphragms in the carb seemed to be fine

Now after doing those things I can prime the carb and it will fire and run...........till the fuel is consumed. Once it actually ran on for about 4-6 seconds...surging at mid-range RPM's. It always dies when opening the throttle.

I did a fair amount of searching/researching on the AS archives and found this thread where someone had all the components needed to make a running engine( spark, gas, compression) ;
http://www.arboristsite.com/chainsaw/180749.htm

Since I've been thru the diaphragms issue with the other two pieces of equipment I KNOW about the flooding out issue. This one is different in that it will always start and run for a burst with the fuel primed in the carb. I don't have the tools to check for bad crank seals but am wondering if there might be something I missed in the carb assembly on this one!??? Thought I'd gotten it down on the other two..........however they were known runners before the deterioration of the diaphragms.

I've also taken the nylon interface plate off and checked the flexible rubber sleeve that attaches the interface plate to the cylinder. Everything looks good there.....the rubber sleeve is stretchy with not cracks or signs of hardening.

Nothing to do with the carb issue/non-running issue but I did a light muffler mod on it and the P/C looks great and the saw has great compression.

I am going to buy a new spark plug for it when I get into town next but since it does start and run briefly I'm not soo suspect of that being the issue!?? Looks like I'll be removing the carb,, taking it apart, blowing thru all the orifices and looking for something obviously wrong in the assembly process............it was late and who knows!!??? I would appreciate your suggestions as it just seems to be something real simple I'm missing!!??

 

[Roanoker494]

Since it runs on a prime but not on its own I will agree that you likely have a carb issue. Make sure your new fuel line is not not kinked off somewhere. You mention checking the boot but what about the little impulse grommet beside the boot? Are you 100% sure you got the gasket/diaphragm orientation correct? I believe those carbs install with the metering side up so on the top it would be the gasket against the carb, the diaphragm and then the cover. The pump side is opposite with the diaphragm against the carb. I would also replace the carb mounting gasket and check the intake block/carb mount for flatness.

There is always the possibility there is something deeper in the carb that traditional cleaning can not remove, may be time to make a new friend who has a ultrasonic cleaner.

 

[XPLRN]

I think you have figured it out!!

Since it runs on a prime but not on its own I will agree that you likely have a carb issue. Make sure your new fuel line is not not kinked off somewhere. You mention checking the boot but what about the little impulse grommet beside the boot? Are you 100% sure you got the gasket/diaphragm orientation correct? I believe those carbs install with the metering side up so on the top it would be the gasket against the carb, the diaphragm and then the cover. The pump side is opposite with the diaphragm against the carb. I would also replace the carb mounting gasket and check the intake block/carb mount for flatness.

There is always the possibility there is something deeper in the carb that traditional cleaning can not remove, may be time to make a new friend who has a ultrasonic cleaner.

That's all good input and I did double check the gasket/diaphragm orientation three times and it's correct.

In thinking thru all this and then reading your input I think the solution to my problem is that the little impulse grommet where the tube goes into the cylinder is GONEZO. This is the first time I'd ever been inside this style of carb mounting/impulse signal routing and I do recall shining my light inside that hole where the tube goes and wondering how it sealed!?? I don't recall seeing any grommet/seal but am going to go check on it as that makes perfect sense.........diminished or no crankcase pulse = no fuel pumping/pressure in the carb.

I'm nowhere close to a dealer sooo I'll probably use a piece of tygon as seal/grommet in there to provide a solution if it is missing (99% sure now that I've thought about it)??

 

[dsell]

Sounds like you're on track. Don't forget the check valve if it has to be primed after it sits a few hours. Also, I'm not sure how your filter is made but I recently had a Poulan fuel filter that caused a problem. The alcohol in the fuel probably lead to the issue. The zinc portion of the filter grew a white corrosion. This corrosion sucked up into the fuel line. The fuel line plugged where it squeezed through the fuel tank. I used a syringe filled with fuel and pushed out a 1/2 inch long plug of white powder. Yes, the saw was improperly stored with ethanol fuel. I know the white Husky filters are weighted, but I haven't taken them apart to see the type of metal or if the metal is encapsulated.

 

[Roanoker494]

A missing impulse grommet could certainly cause the issue, though I don't believe using fuel line as a replacement would be advisable. At the very least you will need a piece of high temp vacuum line.

 

[XPLRN]

Self-induced jerry rigging............

A missing impulse grommet could certainly cause the issue, though I don't believe using fuel line as a replacement would be advisable. At the very least you will need a piece of high temp vacuum line.

I've always been humored by your signature quote; "I do not jerry rig!! I make custom parts from alternative materials."

Anyways I tore back into the Rancher 50 and I was correct that the impulse tube grommet was not in the port on the cylinder. Sooo I ended up in that "custom parts from alternative materials" category with the "missing" impulse grommet. As mentioned before I don't live anywhere close to a Husky dealer. I did call the ones I know and found out that it would be a 'pay in advance and wait a week+' deal so I decided to start looking around at stuff I could make work. After reading your post about high temp vacuum line I decided to nix the tygon idea for a grommet.

Found this material and cut a small chunk off and gutted it........figured if it's good enough to lay against headers it would be good enough to have inserted in the cylinder port for the impulse signal;

Sizing was amazingly close;

Of course after I got all that figured out I was looking around on the floor and found the darned original grommet........must have fallen off when I removed the interface piece that goes next to the cylinder. Now actually comparing what I'd jerry-rigged up it was quite close!!

Sooo even though I'm certain it would have worked just as well as the original piece and was probably a higher grade material I elected to reinstall the original part............amazing how one can chase around a self-induced issue!!

 

[272super]

Keep in mind that a used grommet and intake boot are prime areas for air leaks. If you have any running issues you will want to do a vac or pressure test to test this area.

 

[MtnHermit]

First, glad you found the grommet. Hope it runs well now.

Second, what is the purpose of that port? Part of my continuing 2-stroke education.

 

[XPLRN]

First, glad you found the grommet. Hope it runs well now.

Second, what is the purpose of that port? Part of my continuing 2-stroke education.

Hello MtnHermit! I'm still in 2-stroke 101 but I did learn about that port. The port, as I understand it, directs a vacum/pressure signal from the crankcase to the carburetor. This signal is what makes the diaphragms in the carb function and deliver fuel to mix with the air that is being sucked thru it by the piston going up and down in cylinder. That's pretty basic........I'm sure there are others here that might pitch in and help with the explanation.

Here are a couple of websites that I've learned good info from..........the first one is a AS vendor who should always be checked for vintage parts when you have a need;

Chainsawr Adjustment and Tuning of a Chainsaw Carburetor

This is a manufacturer's website that really helped me to understand the functioning of a diaphragm carburetor. The last three carbs I had to work on were Walbros';

http://wem.walbro.com/distributors/servicemanuals/WAseries.pdf

Hope that helps a bit and don't be afraid to try.........the great folks at AS are a wealth of information and will gladly help you work thru what ever chainsaw related issues you encounter.............have fun!!!

 

[XPLRN]

Keep in mind that a used grommet and intake boot are prime areas for air leaks. If you have any running issues you will want to do a vac or pressure test to test this area.

Good info........after I fixed the problem(not the grommet) it idled well and ran strong......I think my mild MM helped a bit.

 

[MtnHermit]

The port, as I understand it, directs a vacum/pressure signal from the crankcase to the carburetor. This signal is what makes the diaphragms in the carb function and deliver fuel to mix with the air that is being sucked thru it by the piston going up and down in cylinder.

That's helpful. So whether its internal, like this, or an external line to the crankcase, diaphragm carburetors need feedback from the crankcase. Didn't know that, only knew they worked in any position. That little diaphragm gets busy at 10K rpm.

Thanks

 

[Roanoker494]

Glad to hear someone has brought another 50 series Husqvarna back to life, I have a 1990 50 special here that will be getting a closed port 45mm top end shortly.

Husqvarna sure does not deserve any pats on the back for the design of these intakes....... On top of the intake boot and impulse grommet issues you have to be very careful to not strip the threads out of the carb flange, oddly enough the Jonsered 490/590 has the same setup but they used carb studs in place of the coarse threaded screws.

Diaphargm carbs do require a impulse "line" to function. Most use either a external line or it comes driectly through a bolted on intake, though there are a few like the 50 series Husqvarna that try to merge the two.......

 

[XPLRN]

The end of this troubleshooting saga..........

Good info........after I fixed the problem(not the grommet) it idled well and ran strong......I think my mild MM helped a bit.

Sounds like you're on track. Don't forget the check valve if it has to be primed after it sits a few hours. Also, I'm not sure how your filter is made but I recently had a Poulan fuel filter that caused a problem. The alcohol in the fuel probably lead to the issue. The zinc portion of the filter grew a white corrosion. This corrosion sucked up into the fuel line. The fuel line plugged where it squeezed through the fuel tank. I used a syringe filled with fuel and pushed out a 1/2 inch long plug of white powder. Yes, the saw was improperly stored with ethanol fuel. I know the white Husky filters are weighted, but I haven't taken them apart to see the type of metal or if the metal is encapsulated.

Just wanted to confirm that after all the stuff I encountered with getting this saw running the problem turned out to be what 'dsell' had mentioned in the above post. Thanks, 'dsell' for your info contribution.......I'd rebuilt the carb and that didn't change anything......sooo I fished out the fuel filter and changed it........sure was a moment of happiness when it started, idled and ran strong after that missing piece of the puzzle was replaced!!!

I'll post up some pictures of the old fuel filter later.........Thanks again 'dsell' for your info contribution!!

 

[dsell]

Glad you got it running good!:biggrin:

 

[Zippy]

Interesting Thread

Nice to see a solution. Good pics too.

I'd be interested to know what was wrong with the fuel filter - do they really foul up to the point of not working under normal use or has it broken down inside and blocked the nipple ... or what?

 

[tomdcoker]

Nice to see a solution. Good pics too.

I'd be interested to know what was wrong with the fuel filter - do they really foul up to the point of not working under normal use or has it broken down inside and blocked the nipple ... or what?

When I work on a saw that has the white porus filters I replace them. I rebuilt one that the screen in the carb. was full white power. Tom

 

[MtnHermit]

I'll post up some pictures of the old fuel filter later.

I for one would really appreciate those pics.

Thanks