365 special won't richen up on low side

[Mattyo]

I don't think I'll mod this....saw is just going to be sold locally. ...but if you have a link to how to mod the zama that'd be great

Did you ever get another 394?

no... I have a pile of 372 365 stuff I'm working on now, if it gets sold....who knows

 

[jmssaws]

I've still got a few,holler when your ready.

 

[Mattyo]

Yes! Tx

 

[Poleman]

http://www.arboristsite.com/community/threads/zama-carb-mod-cliff-note-version.275905/

 

[Poleman]

Any questions just PM me....

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[Big_Wood]

http://www.arboristsite.com/community/threads/zama-carb-mod-cliff-note-version.275905/

awesome thread although i don't see how a weak pump can supply a larger fuel supply? maybe it's not weak? i got that theory because every one of those zama's i've had so far a new pump diaphragm fixes them. gonna experiment with this the next one i get. i've drilled a few carbs but never one of those zama's

 

[Mattyo]

Thanks guys for the help....gonna run it s bit and see if it runs consistent. ..if not I'll throw a different carb on. Tx

Nice link poleman...tx

 

[Poleman]

If the jets are drilled larger they will flow more fuel. The drilling helps the low end and will increase fuel throughout the rpm range.....but at top rpm a saw can only use so much fuel and is set at a normal need. The time the fuel is increased through the carb is if it's a ported/performance built saw....law of supply and demand. These modded carbs can supply more fuel to a performance saw.

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[Big_Wood]

If the jets are drilled larger they will flow more fuel. The drilling helps the low end and will increase fuel throughout the rpm range.....but at top rpm a saw can only use so much fuel and is set at a normal need. The time the fuel is increased through the carb is if it's a ported/performance built saw....law of supply and demand. These modded carbs can supply more fuel to a performance saw.

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can't help but wanna try this but i still hate those carbs lol last week i bored a tilly296 to near 20mm and filled the aux jet passage with JB. drilled the nozzle same size as the aux jet was. thing ran pretty good but i think the venturi was to big for that carb as it has a stumble off idle now. venturi is close to the same size as the throttle bore now. gonna try boring the throttle bore a bit and use a bigger butterfly. damn shame cause it ran good at 18.25 but i had to test the limits. next one i won't go any further then the 18.25 on that tilly but i still wanna try salvage the one i went to far on.

 

[Poleman]

Lol,I hated the Zamas too before I started messing with them!! Sounds like you have aa good grasp on carbs!!! Did you try increasing spring tention on the needle for a higher pop off? May be over rich off idle causing the stumble.

 

[Mattyo]

ok, I swapped the carb out for the walbro. I'm STILL getting a stumble at high rpm... machine gunning almost... like its being prevented from getting to full rpm. like something's holding it back. so I swapped the coil. better, but still the stumble is there. i just checked the fuel line and pressure tested it, its fine. new fuel filter as well. plug is new....

could i have 2 bad coils? this is getting nuts to get this thing running.

 

[Poleman]

Did you by chance advance the timing??? I've had timing do that. I did all the mods you did to a 5105 and when it gets cold (0) it would do that. I ended up fixing it by outing in a heavier needle spring(or stretch yours a little). You might try that. Yours just sounds hard to pinpoint because of results with Carb swap and coil swap. Both seemed to help but not 100%.

 

[Mattyo]

No timing advance unless the key has sheared. ..

Just trying to get to the bottom of this. ..such a pain

 

[Mattyo]

It starts nice and seems to idle fine and now it revs without being boggy...but it doesn't seem to want to make full rpm...even if I lean it out....it still wants to stumble instead of getting to full rpm smoothly

 

[Poleman]

Whats the plug look like? Is it dark or cream colored? Will the saw lean out know with adjustment on the H? And my understanding it's still stumbeling at high rpm's??

 

[Mattyo]

It seems like the saw does sorta respond to the h screw...but it doesn't get to full rpm...

 

[Poleman]

Does the saw run good for a bit then act up or act funky from the first start and not rev? Have another Carb to try??

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[old guy]

Got water in your fuel?

John

 

[Poleman]

It does sound like that.....

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[Mattyo]

Fresh mix....used on another saw. Works fine on my 372....that one tuned nice.

The carb is all reday swapped.

It sounds like ignition isn't keepin up. ...because it idles fine. Maybe I'll try a 3rd coil.