PIONEER 1074 CHAINSAW FUEL TANK PRESSURIZING, NEED HELP

[pcheffernan]

I own a Pioneer 1074 chainsaw that has recently sprung a spraying fuel leak out the front side of the split of the tank. I rebuilt this chainsaw a few years ago, had the case halves split due to a fuel or oil leak (can't remember). I resealed the case halves with an aviation sealant, worked good for a while, now it has sprung a spraying leak out the front of the tank.

A little history: Originally had a pressurizing fuel tank shortly after the engine was rebuilt, now that the case halves were resealed using Aviation sealant that used for sealing fuel tanks. Never understood why. Replaced the fuel cap (these are non vented caps). Could not find any vent for the fuel tank, so I assumed it was built this way. The original carburetor never worked correctly and would idle bad and flood, I replaced the carburetor (I believe with the 1073 carburetor) and had it rebuilt. The cylinder, and piston assembly has been recently replaced too. The saw runs fantastic like a new old one, but I believe blew the sealant out because of the original tank pressurization problem that I never corrrected.

Looking for an old Pioneer chainsaw mechanic that has some advice on where I can go from here. Unfortunately I will be tearing the saw back apart to reseal the case halves again, I will be using either Permatex no 2, or Yamabond.

My buddy looked up and seen something about a Vernay valve. Is there a problem with these?

I will check the vent tube under the bar side to make sure it isn't clogged.

If there is a better way to vent these things, would like to know if someone has had these issues, and found a full proof way to fix it. Thank you.

 

[b fish]

Never heard of that problem! And probably any old mechanic that would know , doesn’t use the Internet! Just a guess.... I know on my old Husqvarna 61 Practica, that it uses a vented gas cap. Hope you find the answer!

 

[HarleyT]

Have you looked for a gasket?

 

[ray benson]

Take a look at this post and thread about the 1074 tank vent
https://www.arboristsite.com/community/threads/pioneer-chainsaws.70698/page-610#post-6509515

 

[pioneerguy600]

There is plenty of members that can work on Pioneer chainsaws, just click on the link below and ask your question on the Pioneer thread,

https://www.arboristsite.com/community/threads/pioneer-chainsaws.70698/page-647

 

[WoodchuckNorris]

Got a free 1074 a few weeks ago and it also has the problem with gas tank leaking from tank vent tube.
It runs fine and when it gets hot, the 2stroke mix leaks from tank vent tube into the chain clutch area as the gas tank gets hot and builds pressure.

Vent valve is underneath the soft aluminum??? plug below ingnition magnet flywheel. Used a die grinder to drill a hole into the plug and then used screw diver to pry it out by sticking it into the hole made by die grinder, so to not damage the cast magnesium casing.

Below there is a check valve, which I think should only allow air to get into the tank, but no fuel to leak out. Futher analysis showed that the rubber plunger/valve material inside that check valve got destroyed by age/fuel and had consistency of bubble gum.

I'm now trying to somehow fix that valve. Otherwise I probably just install a cheap check valve from ebay onto the fuel vent tube.

 

[WoodchuckNorris]

Removed the internal check valve/tank vent valve, installed new aluminium plug, so the hole is closed again and put on an external check valve from ebay. Pack of 10 costs like $7 or so, much easier than fiddling with the factory check valve underneath the alumiunium dead plug.