Replies by the paragraphs: It sounds like you are pulling air vs solid fuel and need some fine adjustments. Are all fuel lines possibly new or very flexible, strong (from a good pull and very snug to ensure they are air-tight on ext and int fittings? You are giving this Monster a good effort that I feel will pay off soon. Hang In There!!

# 3. This saw does not have a primer bulb. I have read the Walbro general small carburator theory site and vaguely understand what is going on. Most importantly I know that the choke is imployed initially not just for cold but to bring fuel to the carb. On my smaller saws, with primer bulbs, I have always successfully pushed the chokes to half off after the first indication of firing and gotten the saws to start and run immediately. I am not sure that this is what I should expect with this more powerfull non primer bulb saw.

Once you have fuel or indications, you back off on the choke as needed. If I prime the engine manually by spraying 2-cycle mixed gas (from the tank) or carb cleaner in the carb or spark plug hole I will usually not choke the engine on an 85 + degree day or as needed.

#4. I have used erratic starting sequences that have occasionally given me a half to two or 3 second run. My high and low air adjustment screws are set to one turn out as directed in my manual. There is an idle screw that I don't understand. It appears that it presses on some pin on the carb, but I don't understand what it does or where it should be set. In any case, for starting I have the fast idle device activated.

Did you pull the screws and run fine wire, carb cleaner and air through them to verify they are clean and all passages/ports and under the fuel screen? You might try 1.25 turn out initially on the adj screws to see it the results will change then fine tune. The idle screw is simply a stop on the throttle to keep it from dropping to low and stalling. Turn it in to help you to keep it alive in this situation and back off later.

# 5. I was having little or no success until I recalled that vacuum in the gas tank might depress fuel flow and I loosened or removed the cap. I also remembered that one old saw I had for years, often needed a clean or new spark plug to fire it up and I replaced the old plug too, although the old one looked clean, if a little wet (which would make one wonder about whether fuel starvation was an actual issue).

These were good troubleshooting steps and you saw these were "probably" not issues.

# 6. Anyway with those changes (whether effective or not), I was able to get the saw to rev up strongly several times. I believe I was able to get my hand smoothly around the throttle trigger where I would expect to be able to control the idle, but it always died on me after two seconds or less. Then it would take several (or many) pulls and manipulations of choke setting or whatever until it would fire again.

Good sign and it would have been good to have had 1-2 oz of carb cleaner in the fresh fuel at this point. Remember to run the idle screw up and it will help in this case. The excessive choking and Etc w/o firing is what is leading me to feel you are possibly pulling air vs fuel.

# 7. One last issue. The rope nut adjustment is a little odd. After loosening it a little, it pulled smoothly and then after many unsuccessful start attempts, the rope begain to tighten up again. I assumed that I was going to have to remove the housing and lock the nut down somehow because it was probably just tightening back up. But in a few hours, and again next day, I would find that the rope pulled easily again for 10 or 20 pulls before again tightening up.

Did you see any signs of locking Chem or Mech, a worn lock nut or etc was used to lock the nut? I am not familiar with this direct saw. Can you post a pic of the carb area of the saw?

We'll call the Pros, Ewalk and Etc on their direct lines (LOL) if you are not going soon.

I am still working on this saw. The fuel line and filter was and is fine. I took the carb out again and blew out the holes again (even under the screen because it blew loose with the air), and attempted getting wire through the adjustment ports. I couldn't feed the wire all the way but I could feel air coming from each port so they are clear. I now see that the idle screw does adjust the idle directly via a tapered screw driving a lever. I initially set it to just detectably open to let an idea of light in. I have later adjusted it more open etc. when my initial setting didn't seem to be useful.

I am still not confident of what technique is working because I am still limited by the starter pully stiffining up after approx. 40 pulls. I pass out in the 100 degree weather too. But I am hoping that my impressions might make one of you able to direct me in one setting direction, or suggest another failure point.

I can consistantly get the saw to start by setting it on fast idle and choked. After two or three pulls it pops (or occasionally revs up). I take the choke off and it will rev up in a couple pulls if not already reving. I believe that it might continue running at extremely high speed on fast idle, but usually when I release it but maintain throttle trigger control, it revs faster and abrubtly dies. I have occasionally been able to keep it revving while quickly attempting to adjust something. Perhaps up to 15 seconds, but usually much less.

The abrubt stall after high rev made me think it got briefly fuel starved. I don't actually understand the high speed circuit, but I thought a more open setting might bring more fuel and I doubled its setting. I think that MAY have given me some of the longer runs. I had earlier tried opening the low speed screw, but then I read the manual where it says a turned in setting usually gives better idle so I usually leave it set at on revolution out which is spec. or a little in which didn't improve anything.

Anyway, its hot, I'm tired, any more ideas?

Do you have a local Small Engine Shop or Mechanic in your area? In my opinion, it's time for some local experienced help, with eyes directly on your saw. There is no replacement to having experienced eyes directly on the job when needed. My 70s philosophy was to do some initial jobs with experienced mechanics to see what might not be said or read. I hate you have had the bad experience without some local experienced eyes help. As you have expressed, this is too much to deal with in the heat and Etc. Please post the final find and fix.

I had a proMac 610 and encountered this problem and finally took the muffler apart and the screen inside it was completely stopped up not allowing exhoust to escape. after cleaning the screen it ran great

If back-pressure is the problem from a blocked spark arrest screen, it should be an easy find and fix. Plus, check your oil-mix ratio that can be related to this. Most combustion engines are expected to run with "Fire, Fuel, Compression" and Exhaust is known just as well but not mentioned as often. The average mechanic would see and feel the lack of exhaust if the blockage is bad enough (not as much noise and smoke output and oily mess in many cases).

The easy fix was shared on this board. Heat the small screen read-hot (with a lighter, small torch, a small flame in seconds from etc) wire brush the charred remains with no efforts and the screen is clean as new. Most large mufflers w/n have a fine spark arrest screen. They can have restricting carbon in the exhaust port that needs cleaning during preventive maintenance PM (as the screens). They usually w/n shut you down as a screen that has been cleaned attached that you c/n see through initially

I have gotten some very good professional help with my saw and thought it would be useful, if personally embarrasing, to report on the problems solved. In my defense, even the exploded diagrams usually don't show or textually explain the complete function of the metering system and this is the only one I have needed to work on.

Anyway, I had two problems. Apparently the mounting block below the carb was slightly loose. This surprises me because although I had loosened it before I understood how the carb was attached, I believe that I had tightened the screws back up and I hadn't removed the block at all.

The critical second problem was that I hadn't slipped the metering lever (I didn't realize it was a lever) into the metering diaphram button in the center of the diaphram. I haven't attempted to take the saw apart again to see how I might have missed the appropriate attachment when I initially removed the old diaphram. Anyway, that is a critical error and I can imagine that others might make the same mistake.

I made a third error. Not my best series of judgments on one tool! I had noted that my air filter seemed really clogged up and I removed the crud which turns out to be the actual fine filtering material turning it into a fine screen. I will have to rig something to act as a better filter. Perhaps I can edge glue a coffee filter or cloth over the filter screen.

Fortunately, I am living in North Carolina, otherwise known as good old boy central. They were willing to plow into the carb and only charged me $25. They also tested my 20 inch bar saw in a huge log sitting just behind the shop. I was shockingly surprised that it must have cut perfectly straight because I had been admiring 30 cuts (curfs) from various saws all lined up less than an inch from each other in this log. I had been looking at this log while waiting for the mechanic who had taken a small saw out into the woods to return. For some reason they didn't have a smaller log next to the big one and they needed to make serious test cuts before returning a saw to a customer.

After explaining my various saw issues, the mechanic pointed out that there were places who didn't check the saws they repaired and he couldn't understand how they could let a saw out of their shop without practically testing it. Good old boys. These guys repair farm tractors and Stihl Saws. They did my McCulloch anyway.

Chas045, This Is Good News! Thank you for the follow-up info on the repair. Can you post a link or picture of the carburetor that will show the carb related to your statement below. OR! Is the carb attached your carb and the problem was related to #s 10 and 12?

"The critical second problem was that I hadn't slipped the metering lever (I didn't realize it was a lever) into the metering diaphragm button in the center of the diaphragm. I haven't attempted to take the saw apart again to see how I might have missed the appropriate attachment when I initially removed the old diaphragm. Anyway, that is a critical error and I can imagine that others might make the same mistake. "

Did you see this message below related to possibly finding old filters?

http://forums2.gardenweb.com/forums/load/tools/msg081142342586.html?3

Posted by deano_2010 (My Page) on
Tue, Aug 21, 12 at 11:42
Looking for an old Homelite 550 air filter. Any idea who might have one? Looks very similar to a Homelite XL-12 filter. Are they interchangeable? Great old saw, goes through a 4' x 95' Torrey Pine like butter! Thanks in advance for your help.

�h Posted by ewalk (My Page) on
Sat, Aug 25, 12 at 11:03
You may wish to consult the Chainsawr site for this part numerous older saw parts available .

Well, 10, 12 and most critically #7. Admittedly, as I already said, I can't see inside the carb now, and the center of part 7 above is obscured by part 8. I assume that the center of 7 gets hooked to the lever which here is part of #10. That would make the lever pull on 7 rather than push on it as I had assumed. I have looked closely and now realize that one of the color action drawings from walbro does imply this attachment. The exploded view above shows the hook that attaches to the top of the needle 12, and the other end of the lever though hidden is identical and snags the center button of 7 I believe.

Thanks for the thread about filters. I think I will just find a little piece of thin fine foam and cram it over the filter frame.

Please keep an initial close eye on the foam. Know that it w/n deteriorate due to fuel/oil vapor and heat and get sucked into the carb. I know the wire mesh filter. With filth and w/o my glasses I felt I found a Problem. LOL!