Old Homelite Won't Run Right... Need Help!

[Positrack]

I've got an old Homelite 150 (UT# 10432-B) that I'm trying to get running, but I'm having trouble...

The magneto (or coil assembly or whatever the proper term is) had an intermittent open causing a no-spark situation most of the time, so I replaced that. The saw had also pretty much quit oiling so I replaced the oil pump at the same time. Afterward, the saw started right up and ran GREAT. It also now oils like crazy and actually makes a pretty fair mess (it sure is nothing like the oil stingy saws made today). I figured I was golden and called it a success. However, when I took it out to fine tune the carb and do some cutting, after about a minute of running, it started bogging on the top end. It got worse and worse until I couldn't even keep it running. It would still idle (poorly) and low speed (poorly), but as soon as I'd gun it to the point where the HS side probably took over, it would just die. It would act like it was out of gas. I'd have to choke it to get it started, and then it would do the same thing. It got worse the more I ran it until it wouldn't even stay running. I got ****** and let it sit for an hour. When I came back, it started up and ran like a new machine... for a minute, then slowly started into the same BS again.

I did a compression test: 127 PSI

Plug gap: about .025" (strong spark when ground tested)

Plug was just cleaned, but from the little running it did, it looked on the lean
side; ground electrode was whitish, rest of the plug was clean (probably washed from repeated chokings).

It never seized or seemed to get unusually hot, it just acted like it was running out of gas, particularly on the top end. However, when stone cold, it seems to run PERFECTLY. :censored: One odd thing: it would instantly stall at idle when I turned the HS screw in all the way (seated). Is this normal? I would think it should idle fine without any HS circuit at all.

Also, just for now, I'm running 32:1 mix in it. I'm pretty sure Homelite called for 40:1, but I only had the 32:1 (for weed trimmer) and the 50:1 for my Stihl. I wasn't sure if the 50:1 would be okay, but I figured the extra oil in the 32:1 shouldn't hurt at least. The mixture couldn't cause this could it? The gas might be a little old but smelled good. On a side note, would the 50:1 hurt the saw? It sure would be nice to just carry one can for all the saws.

I did take the carb apart (Walbro) to clean it out. It looked a little on the old and stiff side but nothing was real bad (looked pretty clean really). I blew out the passages with solvent and comp. air. I didn't see anything wrong. The saw's got a new fuel line and filter.

I'm no saw expert and I'm at a loss other than to throw a rebuild kit at the carb and hope that fixes whatever is wrong (generally a poor repair philosophy in my experience, but how many things could possibly be wrong on something this simple?!?!). I don't see using this saw a whole lot, but it is a tough, light, and handy little limbing/truck saw, and it was my Grandpa's so it's got sentimental value and I'd like to get it running. Any of you saw gurus got an idea? Thanks.

 

[sefh3]

I'm leaning toward a cracked fuel line. It idles good, which doesn't call for much fuel but when you hit WOT it stalls out and dies (calling for lots of fuel but sucking air instead of sucking fuel).

Replace the fuel filter when you replace the lines too.

Does the saw start right back up? If so usually a bad coil (one that stops when hot) takes a few minutes to cool down before re-fire.

 

[sefh3]

FWIW, that H and L side of the carb should be about 1 turn out. Yes the saw will quit when the H is turned in. No fuel is being delivered.

 

[Positrack]

I'm leaning toward a cracked fuel line. It idles good, which doesn't call for much fuel but when you hit WOT it stalls out and dies (calling for lots of fuel but sucking air instead of sucking fuel).

Replace the fuel filter when you replace the lines too.

Does the saw start right back up? If so usually a bad coil (one that stops when hot) takes a few minutes to cool down before re-fire.

After it warms up or at least has been run for a minute and has started acting up, it will pretty much start right back up but it will need to be choked. If it is actually cold, it will start great, idle great, rev great, and cut perfect. This will last for maybe a minute or less, and it will slowly and progressively lose top-end power, then stumble when the throttle is opened, then start wandering at high speed, and ultimately stalling completely when the throttle is opened. Like I said, it will always restart, but it's performance won't improve unless it sits for a while.

I replaced the coil before any of this started. It actually was bad (no start period). With the new coil, it starts and runs perfectly but then this started. I hope it's not the new coil, but it really doesn't act like it to me. Like I said, I think it's just not getting the fuel it needs, and it gets progressively worse the longer the saw runs for some BAFFLING reason. I did check the spark immediately after running it until it quit, and it still had strong spark.

I checked the fuel line when I put the thing back together and it looked fine. The line and filter are about a year old. However, I guess I will just replace the line and filter since I have the stuff here. I should have just done it on general principles when I had it apart anyway... You're right though, it acts like it's sucking air. Could I have somehow put the carb together wrong and caused this? I'm no newbie to carburetors, but of course it is possible I did screw something up. I AM fairly new to chainsaw carbs. One other thing; there were two rubber flapper valves in the carb. They seemed pretty stiff and as if they might not seal as well as they should. Could this be a possible cause? It just seems so weird that it runs absolutely FINE for a minute or so and then slowly goes downhill to the point where it just won't run.

FWIW, that H and L side of the carb should be about 1 turn out. Yes the saw will quit when the H is turned in. No fuel is being delivered.

Ahh, that would explain it then... Thanks for the explanation, and thanks for the response.

 

[rmh3481]

Sounds like a vacuum is building in the tank. Did you check the tank vent?

 

[Positrack]

Sounds like a vacuum is building in the tank. Did you check the tank vent?

Yes, it certainly does act like that, but unfortunately that's not it. I cleaned out the tank vent very thoroughly and even ran the saw with the cap removed. It still did the same thing. And of course vibrated gas all over creation.

 

[Little Al]

I had a 150 that had a similar problem finally found the cause the fuel pipe had been replaced with to large OD size pipe where it came out of the case it was compressed to almost blocking it off replaced with correct size pipe & problem solved

 

[hotshot]

No top end

I would definitely replace the fuel pump diaphragm, but I'll bet the seive screen is plugged up from old debris in the line. It's located in the body, under the same side cover as the fuel pump diaphragm on that Walbro.

 

[Positrack]

I had a 150 that had a similar problem finally found the cause the fuel pipe had been replaced with to large OD size pipe where it came out of the case it was compressed to almost blocking it off replaced with correct size pipe & problem solved

That would make good sense but that's not it either. The new line is actually a little looser fit than I'd like (through the case). ID is the same as the original line, but I think the wall is a little thinner.

I would definitely replace the fuel pump diaphragm, but I'll bet the seive screen is plugged up from old debris in the line. It's located in the body, under the same side cover as the fuel pump diaphragm on that Walbro.

That would make sense too, but the screen is clean. It wasn't too bad to start with and I cleaned it out when I cleaned the carb. I didn't realize that diaphragm is actually a fuel pump though. The diaphragm and the flapper valves (on the other side of the carb) looked a little stiff but neither were damaged. Still, I just don't see what else it could really be. Maybe I'll just order a carb kit and keep my fingers crossed but I sure hate to just throw parts at stuff without really knowing what's wrong.

 

[polardoo]

So back to basics. You need three things, compression(127 lbs) spark(you know you have some) and fuel. Compression is easy to check and so is spark with the right tools. Fuel can be a sneaky one. So compression is good. Check for spark with a timing light when it is acting up, even new coils can fail. If you have those two, you have your answer. Might need new diaphrams and verify correct installation. By the way, Homie 150 is a wonderful little saw!

 

[pioneerguy600]

If your metering diaphagrm is old and stiff it will not drop down and operate the movement of the needle valve off the seat far enough to allow enough fuel to flow to allow WOT operation, it will allow idle but even spooling up would be difficult. A carb cleaning and a new kit works wonders on old saws.
Pioneerguy600

 

[poulson01]

+1 PioneerGuy.
My 306A runs like new.

FWIW, that H and L side of the carb should be about 1 turn out. Yes the saw will quit when the H is turned in. No fuel is being delivered.

I just did this on Friday with my MS361 while diagnosing carb trouble. It ran pretty well up to 1/4 throttle with the H screw bottomed out.

 

[Positrack]

That's awesome! And it looks just like my saw (well, sort of...). How big a bar is that and what all did you have to do to the saw to get it to pull a bar that big?

If your metering diaphagrm is old and stiff it will not drop down and operate the movement of the needle valve off the seat far enough to allow enough fuel to flow to allow WOT operation, it will allow idle but even spooling up would be difficult. A carb cleaning and a new kit works wonders on old saws.
Pioneerguy600

That sounds just like what it's doing, but I still don't get why it only does it after being run for a bit. Oh well, maybe it's just haunted by the ghosts of the many trees it's dropped in its long life. :chainsawguy:

Anyway, I guess I'll do some more poking with it, but it looks like I'm looking at a carb kit. Thanks to all for the advice; I appreciate it. If anything else pops to mind, don't hesitate to post up.

 

[polardoo]

The pipe was a just for fun experiment, it runs worse with it than without. The bar is just for show! Hey but sometimes cool looks are all that matters. Anyway if you havent run a good running 150 yet youll be impressed so keep up the work:monkey:

 

[Positrack]

Finally got it running!! :greenchainsaw:
The carb kit did the trick, and it runs GREAT now. Thanks to everybody for the advice!

I also wanted to give props to Chainsawr.com where I got several of the parts. I saw their ad on this site, and figured I'd give 'em a try. I'm glad I did. They had what I needed for cheap, and provided super fast service. Couldn't ask for more.


http://www.facebook.com/photo.php?pid=30860510&l=7c3f47a4b2&id=1618238066

http://www.facebook.com/photo.php?pid=30860509&l=c9d73c0d89&id=1618238066

I was hesitant to put this one up 'cause I know I'm gonna catch it for lack of PPE, but I had to show it cutting eh? Anyway, as you can see, this was the test and tune session after I got it going (in oak).

http://www.facebook.com/photo.php?pid=30860511&l=2e52900406&id=1618238066