AM WJ 69 mods

[Deets066]

Ok carb guys, I have here this After Market carb from definate Dave For my 066. It's not too far off but I want to get a little more fuel for long cuts. It doesn't have a removable jet like a 69 does.

What's my next step?

 

[Deets066]

I've thinned the shafts as much as possible and tapered the edges of the butterflies. I took a small amount off the Venturi also

 

[Deets066]

The metering arm was very high, I lowered it to sit flush after this vid, I think that will fix my lean idle but I want a little more fuel on top end

 

[jmssaws]

I've yet to have a carb on mine that wouldn't run out of fuel on a long cut so I'm all ears to deeter.

I've tried drilling every hole i can drill without success.

 

[Deets066]

Where's @Terry Syd at?

 

[GoBigBlue1984]

Anxiously awaiting........

 

[Terry Syd]

Are you guys saying that the carb will eventually lean out as the engine drains the fuel from the wet side of the carb? (fuel flow problem)

If that is the symptom, then it could be the fuel filter, perhaps it may need a cleaner/bigger filter. If the tank is clean, then try running without a filter.

It may also be the diaphragm in the wet side reaching a maximum flex and unable to lift the metering valve all the way. Try raising the metering lever to get more travel (we can fix the idle issue later by shimming the spring). Raising the arm will reduce the seat pressure on the metering valve and make the idle a little richer.

The next test would be to see if the pump diaphragm is impeding the flow. You will have to pull the pump diaphragm out of the carb. Then start the saw with the choke on and once you get it going, don't let the revs drop to an idle or the engine will stop. Do your long cuts and see if the problem has cleared. If the pump diaphragm valves are impeding the flow, there is a mod I'll explain how to do.

Oh yeah, check the tank vent to.

 

[CR888]

Terry is the 2T carb King! His posts have completely changed my understanding of how a carb operates. There is so much more to improved carburation than simply adjusting 2 screws. The gains in torque and throttle response when a carb is giving its max potential are jaw dropping. When many think of improving saw power and performance cylinder porting is what first comes to mind. Now I see the picture different and realise its certainly important but only one aspect of the whole story. I thank him for that.

 

[Stihlbro]

I have a few questions. Some will require some measuring.
1.) where are the H/L screws at when you have it tuned? (Turns out)

2.) Do you have spare Welch plugs?

3.) Pull the pump side of the carb, does the sealing surfaces for the check valves look smooth?

4.) Measure the diameter of the needle and seat opening, compare that to the fuel pump circuit, what is the difference?

 

[Deets066]

I have a few questions. Some will require some measuring.
1.) where are the H/L screws at when you have it tuned? (Turns out)

2.) Do you have spare Welch plugs?

3.) Pull the pump side of the carb, does the sealing surfaces for the check valves look smooth?

4.) Measure the diameter of the needle and seat opening, compare that to the fuel pump circuit, what is the difference?

1. This AM carb tuned at 1 and 1 for about 13,800 rpm. It was just a hair leaner in the vid.

2. No spare Welch plugs, that is what I believed to be wrong with my Walbro 69.


I'll have to get back to ya on 3 and 4

 

[Mastermind]

I'm here to learn too.......

 

[jmssaws]

The carb on my saw tunes perfect. Just shy of 1 and 1,idle is great.

Anything longer than a 30 second cut it will begin to run out of fuel, I can let it come back to a lean idle for a few seconds then go again and the cycle will repeat.

I've had a bunch of carbs on it with the same results. It will keep running but it's lean.

 

[Deets066]

Are you guys saying that the carb will eventually lean out as the engine drains the fuel from the wet side of the carb? (fuel flow problem)

If that is the symptom, then it could be the fuel filter, perhaps it may need a cleaner/bigger filter. If the tank is clean, then try running without a filter.

It may also be the diaphragm in the wet side reaching a maximum flex and unable to lift the metering valve all the way. Try raising the metering lever to get more travel (we can fix the idle issue later by shimming the spring). Raising the arm will reduce the seat pressure on the metering valve and make the idle a little richer.

The next test would be to see if the pump diaphragm is impeding the flow. You will have to pull the pump diaphragm out of the carb. Then start the saw with the choke on and once you get it going, don't let the revs drop to an idle or the engine will stop. Do your long cuts and see if the problem has cleared. If the pump diaphragm valves are impeding the flow, there is a mod I'll explain how to do.

Oh yeah, check the tank vent to.

About the metering arm, it was quite high to start with, and the stem on the diaphragm is longer than a Walbro one.

That being said I lowered the arm last night and put the AM diaphragm back in so I'm only changing one thing at a time. I'll run it first, but if it didn't help I will raise the arm and put the Walbro diaphragm in.

I may also try an 880 filter to see if that has anything to do with it.

Saw runs pretty good for the most part but just want to make sure I'm feeding it plenty of fuel on them long cuts or stumping

 

[jmssaws]

My mind is on the fuel filter now,it's very possible it's from 1993. Lol

 

[jmssaws]

I have raised the arm but it just seemed to make it fat at a idle.

 

[Deets066]

The carb on my saw tunes perfect. Just shy of 1 and 1,idle is great.

Anything longer than a 30 second cut it will begin to run out of fuel, I can let it come back to a lean idle for a few seconds then go again and the cycle will repeat.

I've had a bunch of carbs on it with the same results. It will keep running but it's lean.

I notice that with this AM carb but not near as much with a Walbro

 

[jmssaws]

I have raised the arm but it just seemed to make it fat at a idle.

Instead of tuning 1 on the low it would just tune less and run the same.

 

[jmssaws]

I notice that with this AM carb but not near as much with a Walbro

You remember how mine ran when you was here,even after a short cut it was lean so I've had 3 carbs on it since and there not as bad but still the same problem.
I put a walboro kit in the aftermarket carb and it changed nothing.

On a side note the carb from dave makes the most power but after a 5 second cut the carb needs to catch up.

Terry has me thinking fuel filter.

 

[Mastermind]

I had to gut the filter on the pipe saw. Just left the outer mesh.

 

[Keith Gandy]

The carb on my saw tunes perfect. Just shy of 1 and 1,idle is great.

Anything longer than a 30 second cut it will begin to run out of fuel, I can let it come back to a lean idle for a few seconds then go again and the cycle will repeat.

I've had a bunch of carbs on it with the same results. It will keep running but it's lean.

My 390 was doin that in a long cut. Ended up I partially painted the tank vent up when painting the handle!!