346xp top end rebuild - wont start / not getting fuel

[TreeMe]

Hi all, Hoping you can help me out here.

First time I have ever attempted anything like this so bear with me...I am a complete noobie.

So I replaced the Piston + Cylinder , fuel line, fuel vent, impulse line, intake boot(old one had a ripped nipple going to the impulse line), exhaust gasket and cyl gasket.

I put it all back together fairly confidently and now saw wont start. I only got it to start and run for a split second after putting a tiny bit of mix fuel under the spark plug hole. It is quite apparent I am getting no fuel. However I am stuck as to how to proceed from here because everything is hooked up correctly.

 

[Duce]

Start with simple things first, pinched fuel line under carb support, cleaned carb (stuck needle valve), plugged vent.

 

[TreeMe]

So far all things I have noticed are the primer bulb will not fill up with gas and seems to do nothing. Is this a clue ? Also when I take the gas cap off, the fuel vent hisses quite a bit (brand new fuel vent), not sure if this says anything.

I suppose I need to figure out how to take apart this carb and check it out/clean/replace it ?? This is intimidating. xD

 

[Duce]

Pull that line off of carb and pump primer bulb, gas should come out. If not it's bad bulb, pinched line, hole in new line. I would start there.

 

[huskihl]

I think the short line needs to remain from the carburetor to the purge bulb. The purge bulb should pull fuel through the carburetor, into the bubble, and then back to the tank

 

[popopboat]

Does pumping primer bulb build pressure in the tank?

 

[full chizel]

 

[TreeMe]

ok so I messed with the primer bulb, it now fills with fuel. and yes the bulb now builds pressure in the tank I believe because the vent hisses when I keep pumping it. The carb worked fine the last time the saw was run 6 years ago.

hmm lol

 

[popopboat]

Primer bulb check valve sticking, replace the bulb and you should be good to go.
Had the same issue.

 

[Benwa]

If your primer bulb has different length nipples, the longer one is discharge and the shorter is the suction. If the check valve is bad, it'll cause issues. Pretty easy to check off the saw with some fuel line and small dish of fuel to verify its working properly. For the price, I don't even mess with them anymore. They cause too many headaches. I just put a new one on every saw I'm into. The other place I'd look is to your impulse line. Have you inspected it after install? I know you said you replaced it, but those little horseshoe impulse lines can get bent & pinched off if they're the wrong length. I've also seen some aftermarket base gaskets that don't have the notch cutout for the impulse in the bottom of the cylinder. Not sure if it's possible to get the gasket turned around on those or not.

 

[Benwa]

After rereading your post, I realized you haven't been into the carb. That's the FIRST place I'd go, especially after sitting for 6 years. There should be plenty of videos on the YouTube to help you out with the rebuild. If you can't find one, give me a shout and I'll make one up for you.

 

[popopboat]

*Correction
Bad carburetor jet check valve causes primer bulb to build tank pressure, as benwa said rebuild the carb first

 

[Benwa]

I've seen the check valve in the primer bulb go bad as well. Usually the return line to the tank is only stubbed into the tank a short amount. When the check valve in the primer bulb fails, it'll try and pump air (pulled from the return line to tank) back into the carb. They'll usually start & run though, albeit sporadic and not well. If the primer bulb properly fills up with fuel this probably isn't the case though.

 

[SOS Ridgerider]

I moved this thread to the general chainsaw page. It’ll see more action there.

 

[Wood Doctor]

I suppose this is a low blow, but I do have to ask. Why did you replace the top end (piston and cylinder)? Could be that was OK and the carb or fuel system was the only problem. Usually it's one or the other but seldom is it both at the same time. Just MHO.

 

[Ketchup]

And did you pressure test?

 

[Mattyo]

Sounds like a carb issue like the guys already mentioned...

But first things first... what was the original diagnosis of the reasoning behind the piston and cylinder replacement? If whatever that is ..is still going on....you are just gonna cook a new top end.

I've kitted a lot of carbs to try to bring em back to life. Easier most often to just throw a new carb at it. Oem only here. Best of luck

 

[TreeMe]

Thanks everyone, I bought the saw used years ago as a dumb new climber in my low 20s looking to get into weekend work. Looking back I think he sold me a saw that needed work but I truly am not sure because I knew even less back then about all of this stuff . I used the saw just one day and it started the day good but by the end of the job it was clear something was wrong. I brought it to a local shop who told me the Piston+Cyl was toast at least. It would be too expensive to have them replace parts and fix it for me so the saw sat on a shelf for many years never to be used again.

Now I am a dumb climber in my 30s - Home from work for some odd weeks with a newborn baby and I decided I want to try to fix this 346xp as a fun project. Plus I want to add a saw that size again to my arsenal.

I started by watching every 346xp rebuild video I can find ( Basically, Thanks Mattyo lol ) and after I discovered the ripped intake boot nipple I decided to go for a top end rebuild myself. Ordered everything offf HLSproparts. No pressure or compression tests have been done. If it turns out the bottom end was no good ill probably just call this a lost hand of blackjack for now until another day. Sorry if this hurts to read I never do anything in life the easy way <3

Thank you so much for the input guys, very soon today I will be cleaning the carb and trying again. In between making baby bottles of course.....

 

[Ketchup]

Don’t give up. You need to pressure test the saw. It’s not that hard, just a little tedious and you’ll need one of these…

https://www.tooldiscounter.com/prod...1Iue4_7-GlLmVErpu498MUqZKXEInAq4aAkc7EALw_wcB

Look up some videos about pressure testing a 346xp.

Keep at it and you’ll have a sweet saw and the knowledge to solve most pro saw problems.

Ultimately you may end up rebuilding or replacing the carb, but first you need to make sure there aren’t air leaks. They could be from your work or the original problem that smoked the saw.

Also, dig that old cylinder out of the trash if possible. It may be salvageable and will provide clues to the original failure.

 

[Mattyo]

On a saw like this i wouldn't have hesitated to tear into the bottom end. I wouldn't have thought twice about it. Fresh bearings...seals...rubber and carb go a long way towards reliability. Feel free to contact me if u need a hand further.