OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Trimmers and Brushcutters McCulloch Trimmers & Brushcutters fuel problem on Mcculloch chain saw

McCulloch eager Beaver 3.4ci Model 60013416 Unable to get saw to run at anything except full throttle, saw is surging and trying to die, unable to help by adjusting L and H jets. Set jets per Bruces write up, 1-1/4 open on L, 1 open on H. compression test: 110 psig Cleaned Fueltank, fuel line and filter, disassebled carb and blew out all jets, carb was clean. Thought might have a vac. leak, put automotive high temp sealant on all gaskets below carb except very last one at cylinder, this one was really stuck and was afraid to try to pry loose (this saw has 2 plastic spacers under carb with a total of 4 gaskets). reassemled and saw ran as described above. Prior to this could not get saw to pick up any fuel to carb and could only get it to hit and run briefly by spraying starting fluid in carb. Any advice would be appreciated. Thanks, Geno

Hi Geno, welcome to Outdoorking.

Since the saw can run at high speed but not at low speed, and it surges as you lower the speed, it sounds as if the mixture is lean at low speed. Because the compression is good, there are two most-likely causes of this. One is that the carburetor is producing lean mixture at low speed, and the other is that there is an air leak into the intake system. Because the intake vacuum is high at low speed and low at high speed, an air leak tends to have its greatest effect at idle or light throttle.

I suggest you begin by confirming the lean mixture diagnosis. To do this, partly close the choke as you drop off from high speed, and see if there is some choke setting at each speed that gets it to run well. (If it doesn't have a choke, remove the air filter and partly obstruct the intake opening with a piece of plate. Be careful doing this though, in case it spits - wear safety glasses, and keep yourself out of line with the carburetor's air intake.)

The results of this test will tell us whether it is a lean mixture problem. Once we know that, we can move forward to curing it. Please post pictures of the saw, and of the carburetor, as well as the carburetor brand and type number.

Grumpy, I think your "Lean fuel" mixture was Spot On for the problem. With a combination of almost full choke and opening the Low meter jet about 2 more rounds, I did get the saw to idle, not a real smooth idle, but idle it did! Two of the bolts holding pull rope assembly to saw main frame had been twisted off in the past and I had to crank so much on the saw that one of the two remaining bolts sheared off rendering the crank inoperable (not to mention the same thing to my 70yr. old arm....LOL. I attempted to drill out 2 of the bolts and made a mess of that. This saw was an old family heirloom and nearing 30yrs old with parts availability limited. I had hoped to get it running with minor expense and pass it on to a friend. I decided to just abandon the project. I learned several things about chain saws from tinkering with this one and reading yours and others posts, so, its not all bad. Here's a Texas "Thank You" to you guys across the pond. I look forward to visiting Outdoor King in the future. Thanks Grumpy for the quick response.... Geno PS: I am curious about what you would have advised to cure the lean problem.

I'm sorry to hear about the multiple twisted-off bolts, Geno. If they are tight in the threads, they are difficult to fix at all, let alone without damage, so I understand your decision to scrap the saw.

Having confirmed that the problem is lean mixture, I would have wanted to investigate two possible causes, at a generic level. First, the one intake gasket you haven't checked could be leaking. To test that possibility without wrecking the gasket, I'd have suggested that you place a temporary bead of silicone sealant around the perimeter of the joint (that is, around the edge-line of the gasket, which is the only part you can see). Then, after letting the silicone set, you could see whether it produced an improvement. If it did, you'd know the gasket was leaking, and you'd have had to remove it, and track down or make a replacement. For what it's worth, I think leakage of that gasket was the most likely cause of the problem you had.

If it weren't the gasket, it would be a carburetion fault. The most practical way to deal with that is to just overhaul the carburetor, involving stripping it, cleaning it out by blowing carburetor cleaner through all of the passages (especially the idle progression holes), inspecting the two diaphragms and replacing them if necessary, inspecting the metering needle, checking and adjusting the metering lever height, putting it back together, and checking that the passage through the engine's crankcase that provides pressure pulses to the carburetor's fuel pump is clear. All that is a bit like watchmaking, but it isn't difficult work unless it turns out that you can't clear the idle progression passages or the nozzle check valve without removing the welch plugs. If you have to do that you'd need a more advanced carburetor kit than you'd be likely to be able to get, for that old machine.

If it makes you feel any better, I did the same overhaul on my line trimmer's Walbro WA carburetor last night. There were no difficulties except when I lost the metering lever spring for a while. The problem in that instance seems to have been a leaky intake pipe gasket - the pressure pulsation passage passed through that gasket and it appears to have been leaking to the intake pipe, making the mixture highly inconsistent and the machine sometimes difficult to start. To fix it without new parts I simply put the not-very-flat hard black gasket between two heavy steel plates under the press, and applied two tons force. That flattened it out nicely. Unfortunately the nett result was that the neighbours were serenaded by a line trimmer in full cry at 10 a.m. on Good Friday.

Thanks for coming to us at Outdoorking, Geno. By all means come back if we can help you in the future. I'll close this thread.