357XP idle help

[stihl025]

Okay, got my auction bought 357XP up and running with a new oiler hose to seal the previous leak. Went out today to test it and everything seemed to be fine, at first. It fired up right away, ran good, cut like a dream, but after about 10 minutes of good, hard cutting it would not return to idle. At first, I thought the throttle was stuck, but that was not the case. When I released the trigger, it ran at an accelerated rate, not full bore, but maybe 1/3 throttle. Throttled it back up and released the trigger and it still would not return to idle. I stopped the engine, looked everything over and it seemed to be okay mechanically. I opened the gas tank to find an unusual amount of tank pressure (I can only compare that to my Stihl). I closed the fuel tank and restarted the engine, and voila, it idled again. What should I be looking for?

 

[blis]

from your description i'd say you got stuck air vent in gas tank...

 

[stihl025]

Where do I find that?

 

[Hard Knocks]

Hi Stihl025, I am glad to hear that you got your oiler problem sorted out. I agree with Bils that it does sound like a plugged tank vent. The vent is located on the right hand side (opposite side of the fuel cap) of the fuel tank/rear handle assembly. If you look into the crack between the body of the saw and the spring mounted tank assembly you will see a small round white plug. You may not see it if it is covered with sawdust. These vents are a two part unit consisting of an outer circular dust filter and an inner vent. We are usually able to clean them without removing them by blowing out the sawdust with compressed air and spraying them with brake cleaner. If you can not locate the vent I will try to attach a pic of the location.

 

[stihl025]

I am on it. I'll let you know what I find... Thanks again....

Oh, btw, that part number for the updated oil hose worked like a champ. Not a single drop of oil. Saw runs great, better than I had expected with the exception the vent problem (I think).

Do you use brake parts cleaner or carb / choke cleaner??? I thought the brake parts cleaner would be a little harsh on the plastic, or not?

 

[stihl025]

Ok, I cleaned it with the carb cleaner. Looked pretty good to begin with though. Just tested it out and after making a few cuts with some small stuff, no problems. BUT, I just did full cut through a 20" log and the problem came back. As the saw was running at fast idle, I opened the fuel tank and the saw immediately went back to normal idle. So, I think that we are correct with the plugged vent valve, but I am not sure that cleaning it will cure it.

How hard are they to replace, and what does the part typically cost?

 

[Hard Knocks]

we use brake cleaner and sparingly. It may be fine but I am reluctant to use carb cleaner on plastic parts. They recommend testing brake cleaner on plastics first and not using on rubber parts. We use the brake cleaner because it leaves no residue and is mainly isopropanol and co2. If anyone knows of a reason not to use it for cleaning tank vents please post.

 

[stihl025]

Hmm, back outside I go. I'll give the brake cleaner a try. WTH, the carb cleaner didn't work. LOL

 

[Hard Knocks]

The tank vent is part#501 62 98-01 and the filter is 503 60 04-01. I remove the handle/ tank assembly from the saw to replace the vent. You can probably do it without removing it but I find it easer to get into the hole to dig out the actual vent. I use a dental pick to remove both the filter and vent. Just make sure that you have clean hands when installing new parts.

 

[Hard Knocks]

If you have a hand pump/carburetor pump you can test the tank vent. Just plug it into the fuel line and pump it up to .5 bar. It should drop to at least .2 bar in 60 seconds.

 

[stihl025]

I cleaned the valve with the brake parts cleaner. It seems to have helped quite a bit. Went out and cut up some large red oaks. Seems to "want" to idle a little faster after a big cut, but settles back down fairly quickly. I will keep hitting it with the brake parts cleaner in the next few days to loosen anything else up that may be stuck.

Once again, thanks for the info Hard Knocks

 

[Hard Knocks]

Try to drain the fuel tank (to avoid spilling fuel) and remove the fuel cap. Then hit the vent with brake cleaner followed by a gentle spray of compressed air. This will help the brake cleaner to back flush the tank vent. I have seen these vents give problems with just the inside tip dirty. Being a two part system (vent and filter) it is hard to get at the actual vent to clean it without removing it. If you have to remove it you might as well replace it due to the cost being so cheep. Be careful running the saw if the vent is not working 100%. This will cause lean running and possibly do engine damage! Have you removed the muffler and checked the piston? Not that there is anything wrong, it is just good to know when you acquire a used saw.

 

[stihl025]

Looks as if I am going to have to replace the vent valve after all. I tried everything that was suggested here and, at first, it seemed to be okay. Used it on a fire call today when 2 large pines crashed across the roadway adjacent to the dept. Ran good for the first few minutes, but after it warmed up and the fuel got shaken (not stirred), the built up pressure was causing havoc. Thank God for chain brakes to control the chain, or else, I may have caught my fire gear once or twice. It's hard enough trying to watch for downed wires amungst the trees, let alone handling a not so perfect running saw. What I find to be odd is that it only did that for about the first 20 minutes and then it settled down again. Moral of the story: time to visit the Husky fairy.

 

[Lakeside53]

Tank pressure is normal... your carb needle valve will hold that back easily.. Tank vaccum will cause the saw to run lean and speed up.. If you have pressure then you have other problems causing your symptoms.

 

[stihl025]

Hmm... never thought of it that way...

Okay, based on that, what kind of problems could I be looking at? Just some examples to help troubleshoot...

But, I have a question or an observation... The pressure when I open the tank seems unusally high, very forceful. When I was having the problem today, all that I had to do was crack the gas tank and then it would be fine... immediately. Still seem normal?

 

[Lakeside53]

Are you sure it's pressure? and not vacuum?

 

[stihl025]

Well, I am pretty sure, the gas cap "pops" outward when I open it as opposed to sucking inwards...