Very strange carb problem.

[traffic903]

Poleman, I sealed the welch plug and put a small amount of stretch in the spring. No difference. I then lowered the metering arm again to about 40 thou under top edge and it idles a little bit better. Seems to be getting enough fuel at the top end too but I'm worried that may change mid cut on me at some point and I'll do damage. 40 thou does appear to be a long way below the top edge. Thoughts? Am I living on the edge?

 

[Poleman]

No, you would be on the edge if you lean out the H too much. Your issue is more idle circuit and not High.
Some carbs jets and passages are miss drilled or our of tolerance due to manufacturing issues. I've ran into this and most the time able to repair it.
I'm still puzzled about weather you hold it or its on the ground. I understand the affect on the needle from being on a hard surface but never as pronounced as yours is.
I would say if your idle is better and you have the same working tune your ok and not on the edge. Somewhere your carb is flowing more fuel but your able to slightly control it so it workable with needle and spring adjustment.

 

[traffic903]

Yeah ok. If I am holding the saw (general use) then the idle is pretty solid. But when I put it on the ground (move a log etc) it immediately starts acting up. If I then put my hand on it, and calm the vibrations, it settles down again.
I was concerned that by lowering the metering arm so much I might not let enough fuel through at wot. But it has settles the idle quite a bit. Still nowhere near stable though.

 

[traffic903]

I would just like it to idle nicely when I put it down.

 

[Poleman]

I'e seen the center tab on the diaphram being to long causing a rich condition similzr to what your experiancing but lowering the needl or grinding tbe tab gets thevsame results.
That vibration thing I know is frustrating when your working and movie g wood but what you have going on......I just don' have an explanation.

 

[traffic903]

Yes I checked the tab thinking it might have some extra material, but nope, all good. It has got me stumped. Just gets way too much fuel when vibrating strongly at idle. As has been said earlier, I will look for a used carb.

 

[lone wolf]

If you see one here in the states, I can get it for ya and pop it in the mail, I think the shipping would be @ $15 or so.

Get a hold of Nate.

 

[traffic903]

I know the 390 carbs bolt on, is there much difference in performance? I assume the venturi size differs?

 

[traffic903]

Get a hold of Nate.

Yes I will find one and ask.

 

[lone wolf]

What make and model is that is that carb

 

[traffic903]

The 390 is a Walbro HD 19B or 19C. 044 is 17A (i think off the top of my head).

 

[lone wolf]

Yes I will find one and ask.

Walbro? Is it what is on a 361 also?

 

[backhoelover]

when your testing the carb are you just doing pressure. if so you also need to do vac

 

[traffic903]

Walbro? Is it what is on a 361 also?

The 361 is a different carb.

 

[lone wolf]

The 361 is a different carb.

Well I think you can get one here for 80.00 or less ,what is shipping to OZ from US?

 

[traffic903]

when your testing the carb are you just doing pressure. if so you also need to do vac

I'm quite new to carb testing. Have you got a link to something outlining the vacuum test procedure? I watched some vids on pressure and did as they said. Nothing about vacuum was mentioned.

 

[traffic903]

Well I think you can get one here for 80.00 or less ,what is shipping to OZ from US?

Yes I can get a new one posted for around $115 US, but that equates to $160 Aus. I've got too much into this particular saw to spend that. And having a whole other perfectly running 044 already is making the decision for me. I know I can get an 039 carb, so if it won't be a performance killer I might go that way.