HELP! 345 to 346 swap

[Shane¹]

Can someone please try to help me out here and see what the heck could be causing this weird running issue with this conversion. I have changed and swapped a lot of pieces trying to figure it out I was just curious if someone else had any input on what could be wrong. It runs good for 1-2 short cuts then really starts breaking down longer you run it worse it gets. But as soon as you let it idle a few seconds it comes right back to life for 1 cut

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[Powerstroke Cowboy]

Tank vent plugged, metering valve not set right? Sounds like it's loosing power due to running lean.

 

[Shane¹]

Tank vent plugged, metering valve not set right? Sounds like it's loosing power due to running lean.

I have checked tank vent and even took it out and cleaned it. I put new OEM fuel line and new filter. Swapped carb with actual 346 does the same thing

 

[Ketchup]

Coil or pulse line?

 

[Shane¹]

Coil or pulse line?

Swapped coils and pulse lines between both saws this morning same thing issues stay with 345 swap

 

[old guy]

Just a thought, maybe not enough ring end gap, when it warms up the ring binds?

 

[Shane¹]

Just a thought, maybe not enough ring end gap, when it warms up the ring binds?

I did check the gap I think it was .008 I can't even remember anymore I have messed with so much stuff now

 

[old guy]

.008 shoulda worked!

 

[Powerstroke Cowboy]

Am I right in assuming you've done a leak down test?

 

[Shane¹]

Am I right in assuming you've done a leak down test?

I did it a couple times before and it held pressure and vacuum but it kept developing a leak before because the bearing pocket was worn on the PTO side. Now with a new case it was holding fine when I first put it together haven't checked since but been doing this the entire time. No erratic idle, tune doesn't change and doesn't change running speed while spraying carb cleaner at seals. Just starts cutting out the longer you run it and worse the hotter you get it. I pulled the jug and rechecked impulse. Going to run it again with less timing advance and see if I can get aby difference

 

[Powerstroke Cowboy]

I did it a couple times before and it held pressure and vacuum but it kept developing a leak before because the bearing pocket was worn on the PTO side. Now with a new case it was holding fine when I first put it together haven't checked since but been doing this the entire time. No erratic idle, tune doesn't change and doesn't change running speed while spraying carb cleaner at seals. Just starts cutting out the longer you run it and worse the hotter you get it. I pulled the jug and rechecked impulse. Going to run it again with less timing advance and see if I can get aby difference

Have you treid a new spark plug?

Sounds like you have your hands full Shane.

 

[Shane¹]

Have you treid a new spark plug?

Sounds like you have your hands full Shane.

Yup I have tried new and known good plugs, coils, flywheels, carburetors, fuel lines etc. I am just lost

 

[Ketchup]

My gut says coil. If the idle was changing I would think air or fuel.

 

[Shane¹]

My gut says coil. If the idle was changing I would think air or fuel.

Swapped with known good coil off 346xp

 

[Stump Shot]

Seems to me I recall messing around with one of these saws and the cylinder base bolts bottomed out in the adapter on me just prior to tightening.
Otherwise, all I know is to go through step by step and eliminate what it's not. Starting with is the spark plug wet or dry and go from there where it takes you.

 

[Ketchup]

Seems to me I recall messing around with one of these saws and the cylinder base bolts bottomed out in the adapter on me just prior to tightening.

I remember this as well. Definitely worth running with the top off until it’s hot and then spraying brake cleaner around the gasket. Intake boot could also not have the nipple fully aligned.

 

[Shane¹]

I remember this as well. Definitely worth running with the top off until it’s hot and then spraying brake cleaner around the gasket. Intake boot could also not have the nipple fully aligned.

Intake boot was seated properly pulled the jug and checked it again today put a new one on it for the heck of it and resealed cylinder again. Going to try it again tomorrow

 

[huskihl]

If you’re not running a base gasket, the impulse can get plugged up with sealant if you didn’t create a larger groove on the outside of the cylinder extension or on the aluminum bearing cup. Could also be the bolts bottoming out. Pan could be warping. On the right hand side, you may need to clearance the case so that the transfer tunnels will fit down inside it as well

 

[Shane¹]

This is what it looked like when I pulled the jug today

 

[huskihl]

This is what it looked like when I pulled the jug today View attachment 457085

View attachment 457084

Is that impulse hose kinked? They kinda need to be OEM with the loop in order not to