Leaking hi side valve??

[outdoorsman88]

hello all

I’ve got a Stihl saw (can’t remember the model, I’ll have to post the model when I get into my shed tomorrow) It’s been running rough sometimes recently and a buddy of mine took a look at it and determined “hi side check valve is leaking” he told me if I run it for to long it will lean the saw out or stall it Is this true? it seems to run fine (my hearing is hit and miss with my old age lol) so I don’t know if it needs to be repaired immediately as I need to get some trees cleared on my land over this weekend

I just want to know what issues this hi side leak might cause me if I continue to run the saw as is

I’m not smart when it comes to engine stuff so I feel dumb for asking but I am worried a little

Any input is appreciated

- Dave

 

[Jasent]

I’m assuming your talking about the decomp valve? Simple and cheap fix

 

[Old2stroke]

d “hi side check valve is leaking

Meaningless terminology. Could be talking about the main jet nozzle check valve, need to ask him about clarification.

 

[outdoorsman88]

Jasent thanks for the reply Is there a decomposing valve in the carburetor? That’s where my problem lies

old2stroke I remember him telling me something about a jet in his explanation I’m sorry as like I stated I am clueless when it comes to this stuff what would a leaking main jet cause the Saw to run like? Would it run lean? Or would it stall? I’ve been reading different threads and don’t fully understand what this problem would cause with my saw

 

[pioneerguy600]

When I get asked a question like the one the OP presented my take on it is its best to get any problem fixed correctly if one wants to be safe and save the saw from future damage. Sure, some of us more experienced mechanics can and will run a saw with certain problems because we have a deeper understanding of what makes them work. If you are not sure if a problem will damage your saw further it would be best to get that problem corrected before using the saw again. A high side check valve is not a correct terminology for a carb problem so at best the members here would only be guessing at the real problem the saw has. It does sound like the carb is feeding too much fuel to the engine but that`s just a ,guess.

 

[Jasent]

Jasent thanks for the reply Is there a decomposing valve in the carburetor? That’s where my problem lies

old2stroke I remember him telling me something about a jet in his explanation I’m sorry as like I stated I am clueless when it comes to this stuff what would a leaking main jet cause the Saw to run like? Would it run lean? Or would it stall? I’ve been reading different threads and don’t fully understand what this problem would cause with my saw

Now things are making more sense.

I’d recommend taking the saw to a competent saw mechanic. Carb work isn’t necessarily difficult but if you don’t know the ins and outs you can damage the saw. If it’s leaning out do not run it till it is repaired

 

[Vintage Engine Repairs]

By high side check valve, one presumes a nozzel check valve in the high speed circuit of the carb. It stops air entering at idle. If it bleeds, depending on how much, you’ll have a saw that’s lean at idle, may not idle at all, may have transition issues from the L to H circuit. However if you can get to above 30% or so throttle, it’ll run fine as the nozzle check valve is open anyway to let fuel out. You won’t burn a saw up with a leaky nozzle check valve, but that’s dependant on if that is the issue or not. Ask for clarification and take a picture of the part he’s referring to. The only way to confirm if they are functioning properly is a vac / pressure gauge and check for bleeding.