Fresh 394xp build losing power in the cut

[Mattyo]

Did a fresh build...month long ...to put this 394xp together. Started fine this am...190 compression. ..ran for a few seconds...the stupid decompression valve rattles out.
Shut it off...torque it down . Start it...revs fine...hi and low are fine....again only running for a few seconds... 4 strokes at the top.

Stick it in wood. No power....nearly stalls.

Fresh mix...sharp new chain...it's not the clutch....what else could it be?

 

[strtspdlx]

New intake boot? With or without base gasket? Any machine work?


Regards-Carlo

 

[Big_Wood]

New intake boot? With or without base gasket? Any machine work?


Regards-Carlo

394 uses an intake block. if it's 4 stroking at high speed it should be getting the fuel it needs. fact it has no power and nearly stalls would point me at the metering lever being set to high or gasket and diaphragm mixed up for starters. if the air filter is clean, free flowing, and spark arrestor isn't clogged it's gotta be carburation. i would also be sure your plug gap isn't opened right up or closed up to tight. heck, you might even check to be sure your flywheel key didn't shear allowing the flywheel to move just enough to cause that loss of power. many things it could be

 

[Mattyo]

New muffler and spark screen. Just had one clog on my 350...not that.

The carb has been kitted....but pump diaphragm is impossible to mess up because it grabs the lever..
Not possible to swap pump diaphragm for some thing else.

Air filter is high top...should be good though I can try without filter and see if that helps.

New fuel line and filter. ..it's an am filter but I didn't have this issue with the other 394 I did.

When my 385 had slipped timing it would t start at all....

Hmm

 

[Big_Wood]

New muffler and spark screen. Just had one clog on my 350...not that.

The carb has been kitted....but pump diaphragm is impossible to mess up because it grabs the lever..
Not possible to swap pump diaphragm for some thing else.

Air filter is high top...should be good though I can try without filter and see if that helps.

New fuel line and filter. ..it's an am filter but I didn't have this issue with the other 394 I did.

When my 385 had slipped timing it would t start at all....

Hmm

sounds like you think you have reasoning for everything. i got news for you, it is something LOL JK. when something slips timing it can be alot or very little. the hooked diaphragm can still be screwed up to by the way. also the pump diaphragm only has flaps, you are talking the metering diaphragm. being a prick here LOL get it together matt. you've been here long enough.

 

[super3]

New fuel line and filter. ..it's an am filter but I didn't have this issue with the other 394 I did.

Put an OEM filter on it.
Just because you put a kit in the carb doesn't mean there is not a problem there.

 

[Mattyo]

Man I really thought i knew something. This has got me thrown for a loop.

Super, i hear you.... I just can't understand why a filter would be bad ... its like there is a total loss of compression in the cut.

I'll check the flywheel, though I think this is unlikely it sorta makes sense, or the spark plug maybe... its brandy new though

i'll take apart the carb again, and see whats up there

thanks for the ideas.... keep them comin

 

[super3]

I have no trust in aftermarket filters.
#1 problem that I replace on most saws brought to me for repairs.

Fuel line collapsing?

 

[Mattyo]

Oem brandy new line...

I'll get a oem filter like ya,said

 

[jmssaws]

Does it starve for fuel or just no have any power? 394 is a favorite of mine and I've built more than one,video of it would help. Intake block upside down?

 

[Mattyo]

That might be it! ....the intake partition was not fitting perfectly. ...

 

[jmssaws]

It can b done. It's the only thing I can think of where it would run but play out in the cut.

 

[jmssaws]

The sloped part goes to the top.

 

[Mattyo]

I was wondering why the partition fit better upside down but thought little if it....how come it still runs? Is the issue the impulse line...err....tract?

 

[jmssaws]

Yep impulse. It can pull enough fuel until you hike it's britches up.

 

[Mattyo]

If this isn't the issue I'll eat my hat... very astute...thanks!!! I may even do an addendum to my video series.

 

[jmssaws]

I done it on a old dolmar once and it wore me out trying to fix it. I also own several 394's and have almost done it myself.

 

[Mattyo]

I'll check it late tonight. We will see what I did. I thought it was a pretty good build otherwise

 

[jmssaws]

Terrific saw

 

[Rx7man]

Just one thing to check that I can think of.. the decomp valve does pop ou when it's running?