McCullough Mac 320BV Blower

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  #1  
Old 06-15-08, 01:40 AM
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McCullough Mac 320BV Blower

I recently bought a McCullough Mac 320BV blower. I was told it ran fine, but was hard to start. I was unable to get it going. I changed the gas and spark plug and it started easily. Now it will run fine for 2-5 minutes, then sputter and die as if it's out of gas or being choked. I am then unable to restart it until it cools down. I'm not sure where to start with this since I obviously have gas and spark. Any ideas? I'm also interested in where to get a manual if any one knows. Thanks all.
 
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Old 06-16-08, 09:35 PM
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I've found those to have a tendency toward coil failures. A bad coil will act as yours does. Does yours have spark at the plug immediately after it dies?
 
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Old 06-17-08, 08:43 AM
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I'm not sure. I tried cleaning the carb before you replied and i forgot to note the position of the adjustment screws. I didn't take the limiters off so there isn't a big range, but I can only get it running for about 5 seconds now. I'm using trial and error to find the right settings then I'll test the spark.
 
  #4  
Old 06-17-08, 10:12 AM
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I got it adjusted so I could get it running. I wasn't able to get it off the half-choke though. I also couldn't idle it. I had to have it at full throttle the whole time. I ran it for a few minutes like this. Once I thought it was warmed up I tried letting off on the throttle and it killed it instantly. I couldn't get it restarted and left it for a while. Once it was cold I restarted and tried adjusting the carb to let me turn the choke off. I got about 20 seconds into it and it died again. I pulled the plug and tested for spark. It took me quite a while to find one. I'm not sure if it was because it wasn't there or if I just wasn't seeing it. It was small and easy to miss. I'm taking it apart now to disconnect the kill switch and I'll try again tomorrow. Any hints?
 
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Old 06-17-08, 02:44 PM
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As Cheese said, I'd verify that you have spark first and I'd invest in a gap type tester. These are very inexpensive and available at most auto parts stores.

Let's assume you still have spark. Based on your comments I'd be looking at fuel delivery and specifically, I'd check the fuel filter, fuel lines, and also put new diaphragms/gaskets in the carb. You should be able to blow through the filter easily.

There is a filter screen under the pump diaphragm side of the carb that gets debris in it if the fuel filter was ever off or it had really old gas in it. When you pull the carb apart, just spray all orifices with carb and choke cleaner and it should clean right up. Pay attention to the order that you remove the gaskets and diaphragms on each side of the carb. If you replace them in the wrong order it won't work!

The gasket/diaphragm kit will run $10 or less. I'm not sure whose carbs that Mac used, Walbro, Tillotson or Zama, but you should still be able to find the kit easily. Also keep in mind that a 'repair' kit will also be available for the carb that contains the needle valve, control arm and some other mechanical parts in addition to the gaskets and diaphragms. You need only replace those parts if you believe there are 'a lot of miles' on your unit and they are worn. IMHO, that is probably not going to be necessary.

Keep us posted!
 
  #6  
Old 06-20-08, 11:12 AM
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I haven't gotten the spark tester yet, so we'll see about that soon. I'm sure that carb is clean. I went through it pretty well and I'm sure I put it together right. I also found the head bolts were loose and there was quite a bit of play. I tighted them up. I'll check the spark tomorrow or Sunday. When I do that is it okay to unplug the kill switch at the switch, or is important to do it at the coil. It's quite a bit more work to tear it down to the coil.
 
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Old 06-21-08, 12:12 AM
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The loose head bolts may be your entire problem. Fix that and see what you get, then go from there.
 
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Old 06-28-08, 12:00 PM
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Tightening the head bolts solved the problem. However, I can see a little oil bubbling around the head gasket. I'm assuming that means it needs replacing? Anyone know where I can find one? I also hear an occasional metalic knocking sound. It seems to come and go. Could that mean I don't have enough oil?
 
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Old 06-28-08, 08:51 PM
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If it were mine, I'd run it till it quit and toss it and get a new one. McCullogh parts can be a pain to get a hold of, if you can find them at all, and if it was run a lot with the jug bolts loose, it had an air leak, allowing unfiltered air to enter, causing wear, and allowing the fuel mixture to be too lean, also causing excess heat and wear. It's probably not worth putting a whole lot of effort into it. It may run for a few more years like it is, and that's what I'd do.
 
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