660 clone carb? vacuum? problem.

[Ronie]

Any suggestions on what could cause this, listen right after the cut, in the video I'm trying to adjust it out with the low but it's not working. When I put it together I did a vacuum/pressure check and it was good and right before the video I sprayed around the carb boot with some brake cleaner to see if I had a leak there. Carb is just tuned by ear in the video.

 

[merc_man]

Video says private

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[Ronie]

Video says private

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Sorry, fixed it.

 

[ammoaddict]

Hmmm. I don't have a clue.

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[BuckthornBonnie]

A few ideas-

1. If you throttle up when it’s in that lean state after a cut, does it go way lean on the high side?

2. Tank vent?

3. Fuel filter hanging on the line or plastic piece that holds the cap?

4. My experience… an OEM carb with a fresh rebuild kit solves most wonkey running issues (not all, unfortunately).
5. Is the throttle and plate returning to the correct position on the LA screw? AM 1125 throttle rods are known for being “off.”

 

[Ronie]

I haven't tried to throttle it up while it's doing it, next time I'll see. I did swap the carb a few minutes ago and it still did it.

 

[drf256]

Got a pic of throttle butterfly?

 

[Ronie]

Got a pic of throttle butterfly?

No but I can get one, could it be slow to close all the way? I've tried two carbs on it and it did it with both.

 

[Ronie]

Got a pic of throttle butterfly?

Made a video of it.

 

[popopboat]

No but I can get one, could it be slow to close all the way? I've tried two carbs on it and it did it with both.

We might be cursed
Similar thing overhere (an OEM), except mine goes to excessively rich after WOT, no matter of carb adjustments. Tried different carb, no difference.

 

[srcarr52]

The pulsing after the cut on deceleration is not that concerning, I personally wouldn't worry about it. If you want to fix it you have to increase the pop off pressure of the needle/seat of the carb.

 

[BuckthornBonnie]

It’s doing this with two different carbs, right?

 

[Ronie]

The pulsing after the cut on deceleration is not that concerning, I personally wouldn't worry about it. If you want to fix it you have to increase the pop off pressure of the needle/seat of the carb.

Ok, thanks. So it looks like I have two problems, pop off pressure and most likely a vacuum leak causing it to jump up 1500 rpm after a second or two at WOT.

 

[Ronie]

It’s doing this with two different carbs, right?

That's right, I forgot I had tried two carbs.

 

[BuckthornBonnie]

How does the intake boot look where it enters the box and aligns with the carb? Anything “off” there?

OEM carb for one try, right?

 

[Ronie]

How does the intake boot look where it enters the box and aligns with the carb? Anything “off” there?

OEM carb for one try, right?

Boot is new OEM, it is a litle oval looking but I sprayed brake cleaner around it while it was running and the rpm didn't change. Both carbs are AM, to cheap to buy an OEM one unless I have to.

 

[Ronie]

I was going to wait until this weekend to vac test it but I think I'll have some time later today to do it and check the pop off pressure in the carb.

 

[Ronie]

I was just thinking that when I sprayed the boot I did it from behind the carb box, I'll put the carb on without the pre filter so I can get to where the carb and boot go together and spray it again. I should have thought of that before.

 

[huskyboy]

Aftermarket carbs are *s-word. I would try it with a oem carb and see if it does the same thing.

 

[Ronie]

Aftermarket carbs are *s-word. I would try it with a oem carb and see if it does the same thing.

I know, they are crap and you have a 50/50 chance of them working right but one of the carbs I tried came off a good running saw. If I have to I'll by an OEM one but I really don't want to put another $70 into this kit saw.