346XP Need Help

[emmerth]

I have a 346XP that is approximatley 5 years old. I have cut about 50 cords of wood with it. About 4 weeks ago it started acting up. The RPM's would jump up and then the saw would die. I discovered that if I relieved the pressure in the gas tank (opening it up) that the saw would run fine for another 5 minutes. Then I would have to repeat the process.

I have been told that there is a pressure release hose that is clogged. Is this true???

As of last Friday, the saw lost compression. I removed the muffler and it appears that I need a rebuild. From what I have read on this site, it is not a big deal. I am fairly handy with tools and have rebuilt many 2-stroke engines (atv's and dirtbikes). I will pull the jug tonight and take a better look.

Could the gas problem of caused the damage to the piston/rings? It did sound like the saw needed to get more gas. To much air???

I need some expert advise.

This is my first post but I have visited a few times. From what I have seen, this is an awesome site. Thanks in advance for the advice.

 

[SWE#Kipp]

Check your Pm

 

[SawTroll]

Welcome to Arboristsite!

I am no expert on this, but the acting up that you described initially, could very well be caused by a clogged up tank vent. Check that one whatever else you do to the saw.

However, I suspect that an air leak could be the cause of all your problems.....

- Now, wait for the experts to join in, they sure will........

Here is a workshop manual, in case you need it.

 

[Hard Knocks]

You have likely got a plugged tank vent. This will create a vacuum in your fuel tank and restrict the fuel flow to the carburetor. When the fuel flow is restricted you get a lean running condition that increases operating temperature and reduces lubrication. That is likely what caused your piston and cylinder damage. You must make sure that you eliminate the cause of the problem when you rebuild the saw or you will be back in the same shape in no time.

 

[1wildthing]

RPM jumps up and saw dies. Sounds like it is too lean. Probably either from an air leak or fuel problem. If the tank vent is plugged, it will lean out the saw because of the vacuum in the tank (not pressure). This sounds like it is most likely the problem. Also check to be sure there are no broken fuel lines, and pressure/vacuum test the crank seals. The piston can definitely be damaged from these problems as too little fuel will overheat the motor very fast.

 

[emmerth]

I'll check it out tonight.

I usually pull the plug and check the color when I clean the saw/filter and it has always been a nice milk chocolately brown. Even when I pulled it to do the compression check it looked good.

I hope that I did not do too much damage. Replacing a saw is not cheap. Justifing a new saw to my wife after I just purchased a new 24 ton log splitter will be impossible. But she does like the money that the wood generates. Who knows???

 

[emmerth]

This is a great site!!!!

SWE just emailed me the manual. Thanks a bunch.

From what the manual says, my vent appears to be clogged and the vyon plugs need to be replaced.

Do we have a site sponsor that sells this stuff?

Thanks

 

[TimberPig]

This is a great site!!!!

SWE just emailed me the manual. Thanks a bunch.

From what the manual says, my vent appears to be clogged and the vyon plugs need to be replaced.

Do we have a site sponsor that sells this stuff?

Thanks

Baileys is a site sponsor, as are others, and they would all be glad to help you out on getting the parts you need.

 

[emmerth]

Update

I tore it apart last night. Here is what I found. The piston had some damage on the exhaust side and the ring was frozen to the piston in the same spot. The cylinder had some piston residue that cleaned up nicely with some HD cleaner and mild sand paper. However, there is a very tiny scratch that does not want to come out. It is above the exhaust port and about a 1/4 inch long. If this was on my ATV I would not think twice about running it but I am sure how finicky the saws are.

What are my options? Since I am new to rebuilding chainsaws, should I replace the cylinder, hone it and run it as is, or ...?

I also did the pressure test on the fuel tank and I am plugged. So this will also need to be fixed. Once I get all together, I will do a complete leak down to see if I have any other problems.

Again, thanks for the advice.

 

[1wildthing]

How "very tiny" is this scratch? As long as it is not through the lining on the cylinder you should be able to hone it and put it back on. Hard to say for sure without seeing it though.

 

[HiOctane]

I think the small scratch wont matter the way you describe it,so keep it.And when you gonna check your air vent,remove the two "dimes "in it and without them, check if air is passing tru,sometimes the passage itself block.

 

[emmerth]

Because of the location of the scratch, I doubt that I can get a pic of it. I will try this evening and see what happens.

The best way to describe the scratch is...with the right light, I can see it but I can hardly feel it with using my finger nail.

I think I will see how a honing will do.

 

[blis]

if you cant feel it well with your finger nail it should be no problem, the oil will seal that small scratches...

 

[Hard Knocks]

Go ahead and hone the cylinder. If you can't feel the scratch when you are done and the rest has cleaned up well than reuse it.

 

[emmerth]

It's Alive

I finnally got all the parts from Randy's and was able to put the saw back together on Saturday. New piston, ring, gaskets, vyon plugs, fuel filter, and fuel line.

It fired on the 6th pull and was running on the 7th. I let it warm up and then I shut it down. I let it cool and then fired it up again (1st pull). It seems to be running great. I did this 2 more times. I would give it a little throttle every so often to get the RPM's up.

How soon do you think that I can sink it into some wood?

thanks again for all your help.

 

[blis]

You should start cutting with it immediatly, nothings better break-in than sawing big wood and pushing the saw hard enough for it break-in properly...