camer_1107
ArboristSite Lurker
Hi guys I have a problem that seems strange to me but maybe some of you have encountered it before.
I have a McCulloch Super 250 with the McCulloch carburetor (not the tillotson) that I have been trying to tune after doing some carb work due to the saw running rough (original problem was not enough fuel). That in itself is a long story, but in brief: the diagrams were dried up, but I ended up replacing the top section of the carburetor along with the seals/diaphragms, only because I screwed up the tiny internal check valve and the needle and seat on the old one, as well as that the throttle linkage on the old one broke due to being so worn.
After much screwing around with the new and improved carburetor, I have been able to get the saw to rev up really nicely and to what sounds like top rpms. The problem is, once I let off the throttle, it will idle ok for about 5~10 seconds, then you can visibly see an overflow of fuel shoot into the carb before it sputters and drowns itself in fuel. If I give it some throttle (air) before it dies, it will pause then rev up, I'm guessing because the air has time to match how much fuel the carb is suddenly putting into the intake. This problem also sometimes makes starting it a pain, even when warm.
Here are some details on what I have currently replaced and what it is currently set at:
1. Top of carburetor replaced with other used one.
2. Carb gaskets and diaphragms replaced.
3. Didn't mess with needle and seat settings on new carb top because that is part of the reason I messed up the other one.
4. L screw turned 0.40 turns out.
5. H screw turned 0.50 turns out, haven't gotten far enough to start adjusting this one yet since I believe you need to actually be cutting to do it.
6. Idle governor screw is currently set to a more higher idle position because I was testing the current fuel issue to see if it would still happen at this high of an idle.
7. Compression is 133 psi.
8. Spark plug was replaced with a Champion J8C which has much better spark than the old worn out one.
9. Running 91 non oxy at 40:1 for oil with just a bit of sea foam in the mix.
After 2 hours I have decided to stop messing around because I am baffled and although I do have experience with 2 strokes in general, I am still pretty new to chainsaws and might be missing something. Therefore, I figured I'd go to the experts on this one, so if I missed anything, dont hesitate to ask/mention it.
Thanks in advance for any help, it is very much appreciated.
I have a McCulloch Super 250 with the McCulloch carburetor (not the tillotson) that I have been trying to tune after doing some carb work due to the saw running rough (original problem was not enough fuel). That in itself is a long story, but in brief: the diagrams were dried up, but I ended up replacing the top section of the carburetor along with the seals/diaphragms, only because I screwed up the tiny internal check valve and the needle and seat on the old one, as well as that the throttle linkage on the old one broke due to being so worn.
After much screwing around with the new and improved carburetor, I have been able to get the saw to rev up really nicely and to what sounds like top rpms. The problem is, once I let off the throttle, it will idle ok for about 5~10 seconds, then you can visibly see an overflow of fuel shoot into the carb before it sputters and drowns itself in fuel. If I give it some throttle (air) before it dies, it will pause then rev up, I'm guessing because the air has time to match how much fuel the carb is suddenly putting into the intake. This problem also sometimes makes starting it a pain, even when warm.
Here are some details on what I have currently replaced and what it is currently set at:
1. Top of carburetor replaced with other used one.
2. Carb gaskets and diaphragms replaced.
3. Didn't mess with needle and seat settings on new carb top because that is part of the reason I messed up the other one.
4. L screw turned 0.40 turns out.
5. H screw turned 0.50 turns out, haven't gotten far enough to start adjusting this one yet since I believe you need to actually be cutting to do it.
6. Idle governor screw is currently set to a more higher idle position because I was testing the current fuel issue to see if it would still happen at this high of an idle.
7. Compression is 133 psi.
8. Spark plug was replaced with a Champion J8C which has much better spark than the old worn out one.
9. Running 91 non oxy at 40:1 for oil with just a bit of sea foam in the mix.
After 2 hours I have decided to stop messing around because I am baffled and although I do have experience with 2 strokes in general, I am still pretty new to chainsaws and might be missing something. Therefore, I figured I'd go to the experts on this one, so if I missed anything, dont hesitate to ask/mention it.
Thanks in advance for any help, it is very much appreciated.