Tuning

[StihlEchoingHusky]

First i apologize I don't know part names exactly but hopefully you can follow along.

I'm having trouble tuning my 372 xtorq. The idle is rough and some times when I accelerate it will fall flat on its face and die. other times returns back to "idle" fine. The idle is horrible and will die if I don't feather it. I've pressure and vacuum tested it twice on the last test it held vacuum for I believe it was an hour. It passes a dump test 98% of the time. The carburetor is the OEM xtorq walbro.

I've gone through the carburetor with a ultrasonic carb cleaner solution,replaced everything that I can myself which includes diaphragms, gaskets, metering lever assembly(set to walbro w tool) mixture screws and the filter screen.

I have recently watched a video by vintage engine repair? I believe was the YouTubers name. In the video he talks about a little valve/ seal kinda shaped like the metering lever bobber. The carb he is showing in the video I believe came from a ms180 or maybe a 250. The valve thing is located behind the butterfly valve pivot bar literally beside the bore of the carb itself. Is there a possibility that little guy could be causing the problem?

 

[FederalQ]

I would seat both jets gently then back them off per the illustration on the cover, be it 1 or a partial full turn. If it starts see what the idle rpm is and let warm up and check max rpm. Adjust accordingly then run it under load cutting and listen for the 4 stroke sound when you ease it up a bit in the cut. Something to try in the here and now.

 

[StihlEchoingHusky]

I would seat both jets gently then back them off per the illustration on the cover, be it 1 or a partial full turn. If it starts see what the idle rpm is and let warm up and check max rpm. Adjust accordingly then run it under load cutting and listen for the 4 stroke sound when you ease it up a bit in the cut. Something to try in the here and now.

Ok I'll give it a try. I can tune the OE version of this saw (hd12 carb) with absolutely no problems. Granted if there isn't a air leak but I have a hard time with the xtorq

 

[Ronaldo]

I’ve heard the xtorqs sound different and it’s more difficult to hear the 4 stroking.

 

[StihlEchoingHusky]

I’ve heard the xtorqs sound different and it’s more difficult to hear the 4 stroking.

I think it's got to do with the limited coil. I don't know how much of a difference it will be on a xtorq with high jet to low jet adjustments compared to normal non xtorq. I know generally when you adjust high side you need to fine tune low afterwards. And from what I gather the xtorqs are finicky to tune but can it really be that sensitive? the idle it was rough.

 

[HumBurner]

Obvious question:

Do you have the limiters on the screws still, or have you removed them?

 

[cus_deluxe]

seems like ive heard rwjs can be a little finicky, but ive never owned a saw with one. as said above, remove limiters if present, set screws to factory settings. do you have a tach? either way, tune it so it just stops hitting the limiter, so its regular four stroking, when u find that spot youll wanna tune it in the wood, lean it out slowly until it behaves.

 

[farminkarman]

I used to think I couldn't tune an RWJ carb when I had an xtorq. Then Kevin built me a 2165 with an RWJ carb...I have had no issues tuning the RWJ on that saw. I think it has to do more with the ignition coil they put on the xtorq 372's that makes it difficult to get them tuned right.

 

[StihlEchoingHusky]

I used to think I couldn't tune an RWJ carb when I had an xtorq. Then Kevin built me a 2165 with an RWJ carb...I have had no issues tuning the RWJ on that saw. I think it has to do more with the ignition coil they put on the xtorq 372's that makes it difficult to get them tuned right.

I've tired swapping the coil out before with a non limited black one and this isn't the only rwj-4 I've had for this saw. The one on it is original to this saw from 2012 the other one is the newer style that uses a spline type screw. I've bugged Kevin a few times with other problems and I don't want to over do it with bombarding him with questions. I don't know maybe I just really suck at tuning in general

I can tune the non strato of this saw just fine. I've successfully tuned other 2 stroke products (ms250,260 pro,271,fs56c husky 435,450,460 a 330lk,a pinkway from Amazon and a neo tec bc520) the 400 series are xtorq and I believe the 330lk is aswell but for some reason this 372 has been a real pain.

 

[farminkarman]

I've tired swapping the coil out before with a non limited black one and this isn't the only rwj-4 I've had for this saw. The one on it is original to this saw from 2012 the other one is the newer style that uses a spline type screw. I've bugged Kevin a few times with other problems and I don't want to over do it with bombarding him with questions. I don't know maybe I just really suck at tuning in general

I can tune the non strato of this saw just fine. I've successfully tuned other 2 stroke products (ms250,260 pro,271,fs56c husky 435,450,460 a 330lk,a pinkway from Amazon and a neo tec bc520) the 400 series are xtorq and I believe the 330lk is aswell but for some reason this 372 has been a real pain.

All I can say is that the RWJ on a non-torq needs to be tuned on the edge of too lean. And there is no such thing as part throttle…idle or wot are all it will do well for me.

 

[Stump Shot]

Always tune the high side from a rich condition, this way you can sneak up to the correct tune without the ignition coil interfering with things. So what you will be doing in your log is tuning it leaner until the four stroking finally goes away when cutting and returns when you lift out of the cut.

 

[EFSM]

The idle is rough and some times when I accelerate it will fall flat on its face and die. other times returns back to "idle" fine.

I would suspect that something else could be wrong. The carburetors on them are great for the most part and if it's hard to adjust it could be there is an air leak. I would check out the intake boot clamp and make sure it's tight. Also if it's a high-hour saw check the crankshaft for play--the bearings tend to get loose in the case on them because the case has no steel inserts, just alloy bearing pockets.

I’ve heard the xtorqs sound different and it’s more difficult to hear the 4 stroking.

As noted, this is from the rev-limited coil (something like 13.3k).

I don't know maybe I just really suck at tuning in general

95% of the time someone gives up on tuning, there is something wrong. Someone recently brought in a Poulan because he needed me to adjust the splined screws. Turns out he put an aftermarket carburetor on it, which came with 2 gaskets, and he had put the wrong one between the engine and carburetor and blocked the pulse channel. He admitted his eyesight isn't what it used to be (he wasn't driving himself). He's 84 and spent about 40 years of his life as a head mechanic for United Airlines after working as prototype test engineer for GE turbojets. I hope my eyesight never deteriorates like that.

 

[StihlEchoingHusky]

Also if it's a high-hour saw check the crankshaft for play--the bearings tend to get loose in the case on them because the case has no steel inserts, just alloy bearing pockets.

Brand new bearings. Also I know I said the carb on it is original to the saw but the case itself is new. Id post some pictures but this saw in question is a project/custom saw and I don't want to show it off to the group until is complete. I'll have to look over the boot again. This is technically my second 372 xtorq and the non custom one I had trouble with tuning as well just not as much. Maybe I messed up the pockets when assembling the case halves. I did spin the crankshaft when pressure/vacuum testing it. But that didn't show any problems even when I sprayed soapy water around the crank seals. maybe the introduction of heat from combustion is causing the leak

 

[StihlEchoingHusky]

95% of the time someone gives up on tuning,

Also that's not going to happen I'm to determined to get this one done. This one will more than likely be the saw I use the most.

 

[StihlEchoingHusky]

Is there a possibility that you can damage the mixture screw seats without causing damage to the screws themselves?