Trouble with an 026

[kyle.kipple]

Air filter and tank vent functioning right?

 

[fin460]

Air filter and tank vent functioning right?

Tank vent looks hard and brittle, I have a new one somewhere if I can find it.

How are you suppose to test vents

 

[Duane(Pa)]

Tank vent looks hard and brittle, I have a new one somewhere if I can find it.

How are you suppose to test vents

You can test the vent with vac. Quick & dirty test is crack the fill cap enough that air can seep in if needed. Tank vent trouble is most noticable with nearly full tank. (less airspace)

 

[Duane(Pa)]

I've been around two strokes a long time. I know this: They run like a raped ape exactly 10-30 seconds before they melt...
I had a 372 with a bad tank vent. After I filled the tank, I made a fairly long bucking cut. Half way through, as the saw used some of the fresh mix, it was like someone gave it a shot of nitrous! I mean it flat out ripped. I knew better than to enjoy the experience, and shut it off. Later on, as I was troubleshooting it, I could hear a suction when I opened the fill cap, and I knew instantly what was happening.

 

[fearofpavement]

I just recently had two saws with bad vents. They both acted like they were running out of fuel when the vacuum built up in the tank. ie, bogged down and died, not revved up.
If you've got two running 026's, it's time to start playing musical parts. I've found this to be a surefire way to eliminate possibilities. ie, just because a different carb doesn't run well either doesn't for sure eliminate carb issues unless you can take your carb and run it successfully on a different saw. Replacing a bad part with another bad part can cause you to really expand the search area. Try to verify the parts to the extent you can.

 

[Basher]

Gotta think a bit more on this, but check that the coil hit didn't shear the key.

May wanna try a different flywheel and coil as well. I saw a flywheel magnet go bad once from the polarity changing from a hit.

We also know that advancing the spark timing on these saws will cause an issue much like this. First thing I would check into is to make sure the flywheel is at stock timing, key still in place in crank and flywheel still aligned. If possible swap out the coil, I have found two coil/modules on the hoard of 026`s I have built that have stuck in the advanced timing stage and won`t revert back to the retard timing like they should.

 

[Duane(Pa)]

We also know that advancing the spark timing on these saws will cause an issue much like this. First thing I would check into is to make sure the flywheel is at stock timing, key still in place in crank and flywheel still aligned. If possible swap out the coil, I have found two coil/modules on the hoard of 026`s I have built that have stuck in the advanced timing stage and won`t revert back to the retard timing like they should.

I never knew they did that...what controls the transition?

 

[Basher]

I never knew they did that...what controls the transition?

I havn`t had one torn apart but on other modules its an electronic chip that advances and retards timing, in the retarded position for startup and then advances as the RPM builds. If the advance does not retard when the throttle is let off the RPM`S stay high but the fuel is effectively shut off by the butterfly so I believe a lean condition occurs. On a few saw I have modified and ran this seemed to be the condition when they raced at WOT. Changing the module corrected the problem as the carb could not be enriched enough by adjusting the H to compensate to keep the RPM down. Setting the carb too rich would cause the saw to stumble at spool up and stall at idle.

 

[fin460]

I havn`t had one torn apart but on other modules its an electronic chip that advances and retards timing, in the retarded position for startup and then advances as the RPM builds. If the advance does not retard when the throttle is let off the RPM`S stay high but the fuel is effectively shut off by the butterfly so I believe a lean condition occurs. On a few saw I have modified and ran this seemed to be the condition when they raced at WOT. Changing the module corrected the problem as the carb could not be enriched enough by adjusting the H to compensate to keep the RPM down. Setting the carb too rich would cause the saw to stumble at spool up and stall at idle.

I reset the coil gap, and put some dirko on the seal between intake manifold and back of carb.

Saw would finally run okay on the high side, but the saw would keep racing at an idle, unless the Low screw was screwed in so far that it would run out of fuel before the chain stopped.

I could stop the chain by going out 1 and half turns on the low screw but it would load up and die as well.

I played with it some, checked the throttle linkage was working correctly. The throttle position stop screw was all working, but even with the butterfly completely closed as tight as the carb was allowed, (I looked through venturi and confirmed) the saw would still race at idle.

Since it burbled fine and cleaned up in the cut fine on the high side, I decided it was just the Chinese carb, and it was okay to go try it some at the wood patch. I ran it 5, 10 minutes cutting up some small trees, and it ran as it should, it even started idling better, but I had the chain tighter for safety.

I was planning on putting the original carb back on and seeing if that would fix my idling issues, but now I'm worried my module is stuck in the advanced position since the coil had ran a while in full contact of the flywheel.

I have some other 026 coils, so I will be swapping.

 

[TJ the Chainsaw Mechanic]

Just for the record(unless I missed it), you DID set the gap on the coil at one time and Then there was No gap?

Or you checked it and found no gap?

Cause either something Moved or it wasn't set right. The saw probably ran better once it was scorching hot because everything expanded enough to help seal things and less fuel is required when a saw is hot. Engines like rich cold starts. Have you tried spraying carb cleaner around the engine while it's running? Kinda the red neck way to find a leak but it does work. Just be careful not to get it in your eyes and don't do it when the saw is super hot. If there's an air leak you'll notice a distinct change in engine rpm's. Let it idle and spray around the crank seals and head gasket area. Also you can spray the impulse line as well.

May be different in your case, but I've had several saws with smudge marks on the flywheel and it didn't hurt anything...like said..could be different in your case though.

 

[Bilge Rat]

Some of the chinese carbs tune at 2 to 21/2 turns out. Found this out on a few weedeaters. They run fine with the extra turn.
Chased a similiar issue on a 026 last year. after checking/testing everything and 2 carb cleanings/rebuilds i put a new 194 carb on it. the carb fixed it.

The coil rubbing will cause problems. Readjust the gap and clean any crud, metal filings etc out of flywheel and any rust off the magnet.
Check the wires/connections too. Try a known good coil and if you have another flywheel try it too

Check the crank seals with vacuum test. Go ahead and make some blockoff plates for intake and exhaust.
Aluminum plate and some rubber innertube make good plates that seal well.

Does it have a compression release? They usually leak under pressure but i have one that leaks only under vacuum.

I have a Wild Thing/loaner doorstop that has similar issues.

Good luck and don't throw tools

 

[fin460]

Just for the record(unless I missed it), you DID set the gap on the coil at one time and Then there was No gap?

Or you checked it and found no gap?

Cause either something Moved or it wasn't set right. The saw probably ran better once it was scorching hot because everything expanded enough to help seal things and less fuel is required when a saw is hot. Engines like rich cold starts. Have you tried spraying carb cleaner around the engine while it's running? Kinda the red neck way to find a leak but it does work. Just be careful not to get it in your eyes and don't do it when the saw is super hot. If there's an air leak you'll notice a distinct change in engine rpm's. Let it idle and spray around the crank seals and head gasket area. Also you can spray the impulse line as well.

May be different in your case, but I've had several saws with smudge marks on the flywheel and it didn't hurt anything...like said..could be different in your case though.

while trouble shooting this saw, I found that there was no coil gap, about a week ago, then a few days ago, I reset the coil gap and took the saw out and tried it....

everything before this the saw had zero clearance for coil gap, I put my Miller Mod Saws business card in for the gap clearance, I'm sure he used the perfect size card stock for his cards, lol.

 

[fin460]

Some of the chinese carbs tune at 2 to 21/2 turns out. Found this out on a few weedeaters. They run fine with the extra turn.
Chased a similiar issue on a 026 last year. after checking/testing everything and 2 carb cleanings/rebuilds i put a new 194 carb on it. the carb fixed it.

The coil rubbing will cause problems. Readjust the gap and clean any crud, metal filings etc out of flywheel and any rust off the magnet.
Check the wires/connections too. Try a known good coil and if you have another flywheel try it too

Check the crank seals with vacuum test. Go ahead and make some blockoff plates for intake and exhaust.
Aluminum plate and some rubber innertube make good plates that seal well.

Does it have a compression release? They usually leak under pressure but i have one that leaks only under vacuum.

I have a Wild Thing/loaner doorstop that has similar issues.

Good luck and don't throw tools

I've Pressure tested this saw so many times that the threads in the front of the case on one muffler bolt are very weak. It always passes the pressure and vacuum test. That's while I agree it was probably air leaking at the base of the carb since that's where I block off the intake manifold.

 

[fin460]

And I've used a lot of carb cleaner spraying around this saw as well once the saw gets warm and seems to be air leaking I'll grab a can and spray into as close as I can get to the seals, intake boot, impulse line, and around the length of the case gasket. no distinct changes

 

[Khntr85]

Like @MustangMike said if the flywheel was hitting, the bearing is usually bad, I have seen this multiple times!!!!!!!

 

[TJ the Chainsaw Mechanic]

While vacuum and pressure testing where you rotating the cylinder around to see if it would leak down in certain spots?
Try grabbing a firm hold of the flywheel and see if there is play in the bearing. If it's no good you'll feel movement.

 

[huskihl]

Loosen the idle screw and also the throttle plate screws. Snap the throttle closed a few times to center the butterfly and re tighten the screws

Just thinking out loud

 

[fin460]

Like @MustangMike said if the flywheel was hitting, the bearing is usually bad, I have seen this multiple times!!!!!!!

Brand new oem bearings and seals, I even replaced one seal again because I did a poor job installing it and it was leaking right after I built it.

The coil was hitting the flywheel because I messed up installing it. I set the gap to the wrong side of the flywheel I'm guessing, instead of to the magnet.

 

[fin460]

While vacuum and pressure testing where you rotating the cylinder around to see if it would leak down in certain spots?
Try grabbing a firm hold of the flywheel and see if there is play in the bearing. If it's no good you'll feel movement.

I rotated the crank while pressure testing.

 

[fin460]

Loosen the idle screw and also the throttle plate screws. Snap the throttle closed a few times to center the butterfly and re tighten the screws

Just thinking out loud

I doubt this works here, but I have another 026 that might need this treatment. I didn't know you could do that.