I recently rebuilt a 70s era 076 for a milling saw. I replaced all gaskets, crank bearings, seals, piston, rings, cylinder, worm gear and the drive for the pump. I am running it on 40:1 mix. I have had the normal vibration issues and air leaks that are so common with these saws and think/thought/hope that I have them sorted out. When the saw is cold it starts 1st or 2nd pull, I let it idle for a few minutes to warm up a little before I start to cut. It runs and cuts perfectly for around 5-10 minutes, revs build and fall nicely, it idles well and does not stall out. However, after about 10 minutes it starts to behave like there is an air leak, the revs will rise and fall with no change in pressure on the trigger (I have the trigger lock on as I am using it on a mill and don't always have my hand on the saw handle). I have let the saw stay running when it does this to it see if it sorts itself out and it does not, it always dies within a minute. After such an episode I cannot get the saw started again until it has cooled down completely and unless I let it sit overnight it will not run correctly if I can manage to get it started. Also if I can manage to start it it runs like the choke is on and pours white smoke for around 20 seconds and then will die if I let off the throttle.
I have loctite on the decomp valve, the little M4 bolt perpendicular to the decomp and check them to make sure they don't move. They don't. The intake manifold bolts don't come loose and neither do the nuts holding the air filter base onto the top of the carb. However, I can tell that something is screwy because if I take the air filter and its base off right after the saw stalls the first time the gasket between the carb and the filter base is SOAKED and the filter is very wet if not soaking too. All gaskets from the cylinder up to the carb were replaced again today just to be sure and the same thing happened.
I have not done a vacuum test as I do not have a tester but think that I can rule out an air leak as the saw runs nearly perfectly for the first 10 minutes. I have not replaced the carb or done a rebuild. I have thoroughly cleaned it but reused the diaphragm and other parts. Again not sure that this is the issue as it runs well to begin with. I am running the L set screw 2.25 turns out and the H set screw out about 0.75-1 turn out.
Any help would be greatly appreciated, thanks!!
I have loctite on the decomp valve, the little M4 bolt perpendicular to the decomp and check them to make sure they don't move. They don't. The intake manifold bolts don't come loose and neither do the nuts holding the air filter base onto the top of the carb. However, I can tell that something is screwy because if I take the air filter and its base off right after the saw stalls the first time the gasket between the carb and the filter base is SOAKED and the filter is very wet if not soaking too. All gaskets from the cylinder up to the carb were replaced again today just to be sure and the same thing happened.
I have not done a vacuum test as I do not have a tester but think that I can rule out an air leak as the saw runs nearly perfectly for the first 10 minutes. I have not replaced the carb or done a rebuild. I have thoroughly cleaned it but reused the diaphragm and other parts. Again not sure that this is the issue as it runs well to begin with. I am running the L set screw 2.25 turns out and the H set screw out about 0.75-1 turn out.
Any help would be greatly appreciated, thanks!!
