Carb Guru? WJ-69 and Clone comparison

[srcarr52]

Every carb I have the notch is in line with the hole closest to the intake boot not the hole by the nozzle

Well they are pretty close. Back to the AM carb, it has no notch at all? Does it have idle holes in the bore?

 

[jmssaws]

Well they are pretty close. Back to the AM carb, it has no notch at all? Does it have idle holes in the bore?

Yes,I put everything I could off a oem carb on it.
The needles are different but that's all.

It runs perfectly cold but after a minute it's either idling over 3000 or fat enough that it dies,no in between.
La backed all the way out it will stay idling over 3000 and it's tuned ok for power,not lean or fat but I can barely turn the low out to slow it down and it will but only for a second then it loads up and dies.

 

[jmssaws]

It's completely un tunable. The saw is a hard one to tune anyway but I'm beginning to think I got a saw problem too. It will tune ok with a different carb but still not perfect.

Acts like a airleak but everything is new twice over and been in a bucket of water
Had 3 flywheels and umpteen coils and plugs. Every now and then it has a moment of clarity and runs like a mfr but it's rare. Wtf?

 

[jmssaws]

The carb doesn't tune right on any saw but my 066 doesn't tune good no matter what carb.

It's been in a bucket of water twice with 6psi in it and will hold vacuum forever.
It's just fussy

 

[jmssaws]

Here is what it does,idles to fast,almost 3200 then will load up and almost die then gain rpm back and do it over and over. Throttle response is good and it stays tuned on the high side. What in the hell is causing this?

 

[Mattyo]

by analysis... its erratically getting either too much fuel ... or too little air.

we can surmise that the air flow is constant for all intents and purposes....so therefore, it has to be fuel related, some how, it starts randomly running rich,...nearly dying, and back up... etc.

 

[Mattyo]

I've had it happen w/ the AM 372 carbs...boy is it annoying....and there HAS GOT to be a real explaination

 

[Adirondackstihl]

Have you tried running it without the v-stack?

 

[jmssaws]

Have you tried running it without the v-stack?

I've tried everything.
Out of 10 or so carbs I've had on it the wj34 that's on it in the video is the best idling one,I've never seen a saw go from lean to fat and recover then do it again.
The am carbs are worse but every carb does it.
If I richen it to slow the idle it will load up and die. It's tuned pretty good cause after a 30 second idle throttle response is crisp and if one is even a little fat it will bog,it's at 13.8 and stays dead on but the idle is wearing me smooth.
I just don't get it

 

[1990Husky262]

At first it sounded like it was only the after market carbs you were having problems with but if your saying it does it with all the carbs you have tried and its doesn't have an air leak. Your probable going to disagree with this but how about trying to put a stock muffler back on it and see how it idles with more back pressure if you haven't all ready tried it.

 

[srcarr52]

It could be low back pressure but I mostly think you are being overly critical. Almost every 2 stroke will idle high for a few seconds after being run WOT, then the fat idle circuit will cause a little loading up and it will come down. But they have to be fat to have good throttle response.

It seems to loop nicely once it comes down off the high cleaned out idle and has great throttle response from there. Seems like everything is fine to me. As long as the WOT tune is consistent and it can low idle for a few minutes without dying I'd say its doing really well.

 

[Mattyo]

I really don't think everything's fine. srcarr52 ....you have way more exp than me, but seeing an idle like this doesn't make any sense, especially because these types of idle DO tend to load up and die, or be spinning the chain erratically.

the muff doesn't make sense that its a problem because its a completely static item... the carb is not static, and likely where the issue lies... the question is what... is the hole for the butterfly in the wrong spot, etc??? needle abberrantly not seating properly etc

 

[Adirondackstihl]

 

[jmssaws]

I am picky but it's not right,I'm gonna try a muffler later.

 

[Mattyo]

i'm ok w/ low idle... as long as is sound healthy....so it isn't gonna die... these carbs make idles that sound like they're just barely hangin on

 

[srcarr52]

I really don't think everything's fine. srcarr52 ....you have way more exp than me, but seeing an idle like this doesn't make any sense, especially because these types of idle DO tend to load up and die, or be spinning the chain erratically.

the muff doesn't make sense that its a problem because its a completely static item... the carb is not static, and likely where the issue lies... the question is what... is the hole for the butterfly in the wrong spot, etc??? needle abberrantly not seating properly etc

Its pretty normal for a ported saw with easy flowing muffler to have a lumpy idle. With large ports and large durations the vacuum draw at idle to the carb isn't as strong which causes fuel puddling, poor atomization, inconsistent fuel delivery and thus the lumpy idle. You could put a smaller bore carb and get it to idle better but you'll sacrifice power.

The variation in the idle RPM is still below the clutch engagement so there is no worry of spinning the chain. Most saws wont load up and die, they'll deal with the extra fuel spurts which causes the idle to drop, then the loss of RPM will lessen the fuel dramatically and RPM will raise and start the cycle all over again. If they load up and die then you need to change you ignition timing or stiffen the metering spring and lower the pop off pressure to get more consistent fuel flow at low demand but maintain it at high demand.

 

[jmssaws]

I have tuned a couple ported saws and never had one do like it does,it also just started doing it is why it's bothering me.

 

[Mastermind]

Have you tried stock ignition timing and a stock muffler Jason? We might learn something here.

 

[jmssaws]

Have you tried stock ignition timing and a stock muffler Jason? We might learn something here.

The ignition is stock in the video but the muffler is far from stock.
Why I'm so puzzled is one day it just started doing it and I can't make it stop.
I put a new piston in it when I got it and I even switched back to the old one trying to figure it out. Only thing I haven't changed is the muffler but it's always been on there so I don't know what could have changed but I'm going to switch it.

The saw is incredibly strong but it comes and goes,it's always stout but every now and then it's insanely strong for no reason. It just started that to.
I might make 10 cuts and shut it off for 10 min and go again and it will be noticeably stronger. Something is off because sometimes I can beat it and sometimes I can't even get close,I notice when it's off it looses a little pop out the muffler,it has a different exhaust note

 

[srcarr52]

The ignition is stock in the video but the muffler is far from stock.
Why I'm so puzzled is one day it just started doing it and I can't make it stop.
I put a new piston in it when I got it and I even switched back to the old one trying to figure it out. Only thing I haven't changed is the muffler but it's always been on there so I don't know what could have changed but I'm going to switch it.

The saw is incredibly strong but it comes and goes,it's always stout but every now and then it's insanely strong for no reason. It just started that to.
I might make 10 cuts and shut it off for 10 min and go again and it will be noticeably stronger. Something is off because sometimes I can beat it and sometimes I can't even get close,I notice when it's off it looses a little pop out the muffler,it has a different exhaust note

Is this the saw I built?

I've seen partially plugged impulse barbs on stihl cases that cause all sorts of wonky issues. Next time you have it that far down poke a drill bit through it and make sure it's clean.