$25 course in 2 cycle engine repair

[bryan]

I picked up a Homelite Timberline 45 cc yesterday of CL. Poster said it had an issue in chain not staying on. I figured it was simply that the chain was broke in it got loose. Got there and got a different story. Husband of the poster said the issue was it wouldn't cut even with a new chain. I figured maybe an issue with the clutch. In either case for $25 I could play with it guilt free and learn something in the process.

Got a chance to fool with it today. After washing out the airfilter (lord it was dirty) and making sure the muffler wasn't choked with carbon I gave her a few pulls and she started right up... as did the chain. After adjusting the idle which was way too high and trying my best to adjust the carb with the limited adjustment it has (darned CA regulations), Try as I may I couldn't find a setting where the motor didn't bog down when I opened the throttle (spark plug?). I tried cutting to see if the motor bogged, chain stalled... No it spins the chain just fine and makes a nice but small pile of dust. The original chain was on there and boy it had seen better days.

After shutting it off for a few minutes to inspect the chain I tried to restart but it didn't want to start right up which was surprising as when I was adjusting the carb I had shut it off a number of times and it always fired right back up without the choke. I went to use the choke and noticed it wouldn't fully choke. Opening it up I saw the choke plate was jambed. Long story short the screw holding the choke plate to the pin it spins on got loose, the plate rotated and being it isn't symmetrical it kept it from moving its full range.

Anyhow while trying to figure out why the choke plate wouldn't close I pulled the carb and detached the two fuel lines what surprised me was how much fuel started pouring out of the line. Is this normal? If the tank was under that much pressure why wasn't the fuel pouring into the carburetor? Is there a diaphragm in there than shuts off flow?

 

[dougand3]

Yes, when you pull fuel lines off carb, gas will spurt out. Loosening fuel tank cap should help. I keep galvanized nails of proper diameter - ready to ram into fuel line. Normally, there are 2 diaphragms - metering and fuel pump. They regulate flow. I'd take carb apart and check fuel screen for debris and varnish. And blow out tubes with carb cleaner. Lotsa videos on youtube on how to do it. Get the carb model # - bet it's a Zama or Walbro. Then you can order a rebuild or gasket/diaphragm kit (if needed). Zama models go like CIQ-H42 and Walbro go like WT-973.

 

[kenskip1]

Personally I would have just removed the low speed limiter cap rich en it up and have at it. All that you have mentioned sounds like a lean running condition.I can't tell you to remove the caps but it would be a very simple solution to your problem. You obliviously have an adequate gas supply so this is not an issue.Ken

 

[dougand3]

Like Ken says...if you have plastic limiters - you can cut wings with box cutter or coping saw. If screws are recessed and no slot for flat screwdriver, you can dremel them in. Note the "L" and "H".

 

[bryan]

Thankfully they aren't recessed....sounds like they are going to get Exacto'd off.

 

[clemsonfor]

Yea u sound lean at idle. Is chain on right? And the needle in the fuel path to Carb is what cuts off fuel flow when gas not needed by Carb.

 

[bryan]

Chain was on right, but was dull as can be. I sharpened it up and its gave me chips when I used it rather than a pile of dust. Tuning it has been a challenge. The proper idle adjustment is so dependent on whether it is warmed up or not. Getting it to idle cold results in a too fast an idle once it is warmed up so I found myself adjusting the idle as I went along. I cut off part of the plastic tab for the Hi adjuster and was able to get it 1/4-1/2 a turn richer, but still not quite right as it still lags/stalls if you open the throttle too fast. I can cut some more off so I can get a richer. It cuts okay (actually great compared to my electric Craftsman, but it does seem like the chain stalls too easily. I took off the spur sprocket and made sure it had a clean mating surface with the clutch but haven't cut since I cleaned it so not certain if that helped or not.

The one thing that freaked me out was at one point I couldn't get the saw to stop running. I hit the toggle for it to switch off, but it continued to run for about 10 sec before it stopped. Not certain what that means. Only did it when the saw had just been heavily run..

And for the record Clemonfor I got my Ph.D at Clemson in 05. New a girl over in the forestry dept. Elizabeth Blizzard.

 

[clemsonfor]

Yea I'm sure Liz likes her name on the net Ha But yea I knew her. We were there same time. I got undergrad in 04 and masters in 06. In forestry.

Sounds like you may need to clean the Carb?? Bit if it hesitates its still to lean?? U want to tune it for Max idle it l screw then back ur idle down. And u tune a saw hot. If it won't idle cold its just cold natured. If it won't shut off it sounds like its deiseling? Is the plug clean?
U can always stop a saw with the choke too if it won't cut off.

 

[clemsonfor]

Will it respond to u turning the L screw? Or is the thing all over the place? How old is this saw u think?? I'm starting to wonder if there may be a crank seal issue?

 

[bryan]

It responds to the "L" just fine and I can go from too rich to too lean with it I assume it was running too lean at WOT under load causing it to overheat,which was causing the dieseling. Sounds like I should just get a carb kit, and a plug just so I know those aren't the issue. Saw itself doesn't doesn't seem that old and I think its the original chain that I'm using. Previous owner claimed it worked fine, and then had issues so he bought a new chain but that didn't solve the "not cutting like it used to" issue. I have both chains and the one on saw must be the original as the other looks essentially unused.

 

[clemsonfor]

To lean at WOT would have to do with the H screw not L. Deiseling or runaway on a 2stroke is from carbon glowing or something hot enough to ignite the fuel without any spark as you have killed that by cutting the ignition. Your h screw won't effect your idle. Will this saw burple or 4 stroke at wot? Like when u rev it up wot out of wood is the saw sound rough and gurgeling wot or is it a clean super high rev sound to the top? It needs to 4stroke at top to know ur getting adequate fuel under load and also the 4stroke keeps the saw from running away and gernading on u. Shoot me a pm I may be able to help.

 

[oldspark]

Crank seals? My stihl sorrta acted like that with bad crank seals, wont pull the gas in like its supposed to.