What happens if I run saw without tank vent valve (MS250)

[MMFoF]

Hi, I know that's a dumb question in the sense that I should just run it with the proper part. But I have ordered one and am waiting for it to arrive, and am wondering what would happen if I tried to run the saw without it? I know the idea is to let air in and not out, but I thought that would be to provide atmospheric pressure and avoid a vacuum build up in the tank. So what happens if there is no valve there? There would be no vacuum build-up, but what's the down side - would I have fuel spewing out of the hole where the vent is supposed to connect to?
Thanks

 

[Mad Professor]

Hi, I know that's a dumb question in the sense that I should just run it with the proper part. But I have ordered one and am waiting for it to arrive, and am wondering what would happen if I tried to run the saw without it? I know the idea is to let air in and not out, but I thought that would be to provide atmospheric pressure and avoid a vacuum build up in the tank. So what happens if there is no valve there? There would be no vacuum build-up, but what's the down side - would I have fuel spewing out of the hole where the vent is supposed to connect to?
Thanks

Yes. Not sure if you can rig up a vent using fuel line and grub screws like Stihl did with it's older saws.

 

[ballisticdoughnut]

It will leak fuel if rotated clutch side up but other than that it will run fine.

 

[cscltd]

Fuel leaking out would be first problem-second would be dirt getting into tank
So best to replace it

 

[Mad Professor]

It will leak fuel if rotated clutch side up but other than that it will run fine.

Fire hazard too

 

[David Ellis]

It will leak fuel if rotated clutch side up but other than that it will run fine.

This is exactly true for my Husqvarna 350.

 

[David Ellis]

The saw will run but it will shut down eventually because of tank vacuum.

Hm, no.

I think you failed to read the entire query. The author asks what happens if the vent "valve" is missing. If the vent valve is missing, the saw will leak some gas while laying on it's side.

If the vent hole is plugged, the saw will indeed shut down due to tank vacuum. Yup.

 

[Khaos]

Hm, no.

I think you failed to read the entire query. The author asks what happens if the vent "valve" is missing. If the vent valve is missing, the saw will leak some gas while laying on it's side.

If the vent hole is plugged, the saw will indeed shut down due to tank vacuum. Yup.

Yeah relized that after posted and assumed he would plug it untill he got the part.

 

[stihltech]

Find a short sheet metal screw (#4 or #6 would be the one). Insert it into the end of the hose, but do not bottom it out. Now you have a similar vent to old style. Temporary use only.

 

[MacAttack]

My emergency fix would be a cotter pin with a piece of felt, like McCulloch vented oil tanks on their old saws.
My McCulloch 450's oil tank literally has a hole with just a cotter pin stuck in it for a vent haha. Oil just runs right out of it if it's tipped with the clutch side facing toward the sky.