Carb Guru? WJ-69 and Clone comparison

[Mattyo]

I have 3 of the 69 clones,at wfo they might make a little more power than a oem one but they hunt at a idle. They idle ok but it drives me crazy to here it going up and down.

I'm no carb pro so I'm sure someone can get that out of them.

Ya...
Carbs with 2 idle levels. Annoying for sure.

I wonder if the needle spring is not set strong enough....ie too much possibility for a resonance at idle....making it cycle up and down?

 

[Terry Syd]

The metering spring pre-load, rate and size of the metering orifice are all elements of the idle and ramping in of the low speed circuit. If you start shimming up the metering spring, the idle will get a bit leaner and the ramp is slightly more delayed - in other words you change the tune of the carb. I'm thinking that working with the 'pulse chamber' may be the best way to approach the problem.

It is going to be a long time before I wear out another diaphragm, Hell I haven't cut wood in two months and probably won't be for another two months (medical operation and recuperation). I've wanted to see if the metering spring between the lid and the diaphragm in the pulse chamber would smooth out the idle, perhaps someone with a carb that is giving an erratic idle could try it.

In order to center the metering spring over the center of the diaphragm, you could drill a small indent inside the lid that the metering spring would sit in. Then holding the carb upside down, you move the lid 'up' into position so the metering spring stays in position. I don't know if the mod will work, and if it actually does, what kind of spring pre-load would be required - that's something a modder will have to work out.

If the mod did work to create a more consistent idle, I expect a lot of guys would like to know about it.

 

[Adirondackstihl]

Gluten free funnel cakes?

 

[jmssaws]

The metering spring pre-load, rate and size of the metering orifice are all elements of the idle and ramping in of the low speed circuit. If you start shimming up the metering spring, the idle will get a bit leaner and the ramp is slightly more delayed - in other words you change the tune of the carb. I'm thinking that working with the 'pulse chamber' may be the best way to approach the problem.

It is going to be a long time before I wear out another diaphragm, Hell I haven't cut wood in two months and probably won't be for another two months (medical operation and recuperation). I've wanted to see if the metering spring between the lid and the diaphragm in the pulse chamber would smooth out the idle, perhaps someone with a carb that is giving an erratic idle could try it.

In order to center the metering spring over the center of the diaphragm, you could drill a small indent inside the lid that the metering spring would sit in. Then holding the carb upside down, you move the lid 'up' into position so the metering spring stays in position. I don't know if the mod will work, and if it actually does, what kind of spring pre-load would be required - that's something a modder will have to work out.

If the mod did work to create a more consistent idle, I expect a lot of guys would like to know about it.

I will add that the 3 I have all were ran on ported saws with big ignition advances with 200%+ muffler mods.
They don't tune for a great idle anyway but don't have any problems with the oem carbs.
The am carbs would tune easily and idle fine for just a second then go lean or fat then you could tune it back right but only for a second. I couldn't get one to stay tuned of the high either.
I put a kit in one but didn't change anything.
I want to fix one but ain't sure how.

 

[Mattyo]

Would love to have that answer too j

 

[jmssaws]

If I make 10 consecutive cuts and stop to check rpm between cuts I'd have to adjust the low for either lean or fat and almost always fatten up the high.

 

[Mattyo]

Did you try oem component kit in the am carb? ..needle....diaphragm etc?

 

[Mattyo]

I was just thinking....the needle itself spins in its hole. If it's out of round
....or the hole is out of round...or off center? Then the fuel delivery would be erratic

 

[jmssaws]

I put a oem kit in it.

 

[Terry Syd]

I'm wondering if the check valve in the main discharge nozzle may not be seating correctly. At an idle there isn't enough low pressure at the venturi to draw fuel. Under those conditions, the nozzle then provides a passage for air into the wet side of the carb. What happens is that instead of pulling the metering diaphragm down, it is easier to suck air through the nozzle - thus we need the check valve in the nozzle for idling.

Maybe after a while idling the check valve shifts around and seals again and the result is a variable mixture ratio at idle. If you have a good carb, you could try swapping the discharge nozzles and see if that fixes the problem.

 

[jmssaws]

I'm wondering if the check valve in the main discharge nozzle may not be seating correctly. At an idle there isn't enough low pressure at the venturi to draw fuel. Under those conditions, the nozzle then provides a passage for air into the wet side of the carb. What happens is that instead of pulling the metering diaphragm down, it is easier to suck air through the nozzle - thus we need the check valve in the nozzle for idling.

Maybe after a while idling the check valve shifts around and seals again and the result is a variable mixture ratio at idle. If you have a good carb, you could try swapping the discharge nozzles and see if that fixes the problem.

I'll give it a try. Thanks

 

[GoBigBlue1984]

Dave, I still couldn't get mine (wj-69 clone)to tune correctly on the ported 660. Idles fine but the H is closed and it's still too rich. I swapped out an OEM wj-69 rebuilt carb for now. I tried positioning the washer/o-ring but to no avail. Everything else internally looked good though to me.

 

[Terry Syd]

If it has an auxiliary high speed jet, then you can block off the jet with some GB Weld and just use the High speed needle to tune. If you want to test the idea, just use a dab of silicon gasket sealer over the jet for the test. If it works, then go back in and block it off with the GB Weld.

 

[Moparmyway]

If I make 10 consecutive cuts and stop to check rpm between cuts I'd have to adjust the low for either lean or fat and almost always fatten up the high.

Your ear is very sharp, and you're probably dialed in to a saw better than most. I will say that the two stock saws that I put the carbs on are still being used without any complaints.

I'm thinking that the tree guys running my two either don't have the problem or just can't tell if it's hunting

 

[Mattyo]

The hunting is obvious. ...to any ear

 

[jmssaws]

What I'm having at a idle 90% of people wouldn't think about it but I tune saws everyday that are difficult to tune and I can't keep these tuned,they run great but don't stay put.

If I cut 5 peices of wood today I'll tune the saw before I do,if I use the same saw the next day for 5 more I'll tune it again,I'm not so much tuning as checking and the am carb might be way off.

I said before that it will hunt idling but it's more a little lean then 5 seconds later it's a little fat which could be tolerated but the high is more the problem,tune it to 14k and run it a minute then check it and it will scream lean way past 4 stroke, slow it back down to 14 and it will do it again and again. All 3 I have are like that on multiple different saws.
They will tune around 1 and 1 and always be there close but I always have to turn on it a fuzz one way or the other.

I'll say it again,there good running carbs and I whish I had a couple more that haven't been tampered with by me to see if it's them or me being to damn picky.

If it doesn't tune perfect I go to looking for at problem,probably is me. Lol

 

[GoBigBlue1984]

This one I've got Jason the high is completely closed and still smoking, putting mix out of the face of the muffler.

 

[GoBigBlue1984]

4 stroking like a sunuvabitch lol

 

[jmssaws]

Mine will tune very fast just won't stay there. I would call it a airleak but it does it on the 10 or more saws I've had it on.

I can put a kit in one and it changes nothing. Acts like a carb with wore out needles.

 

[Definitive Dave]

The weird needle shape makes me wonder if they just ran out of the right needles and stuck something else in there. the prior batch of 20 I had gotten seemed perfect after going to a fourth vendor to find a decent 066 replacement carb.
I thought I was home free and ordered 100 and now it seems like about 1/3 of the ones that are out there tune all funky