# Mc/Culloch Mac 160S chainsaw start question



## Dale1 (Nov 13, 2013)

I'm working on the Mac 160S two cycle that doesn't want to start. I have spark and compression. I've tried spraying starter fluid in the carb and also in the spark plug hole without getting the engine to fire ..which would point the problem to the carb.

In past situations of this kind with two and four cycle engines, I've almost always been able to get the engine to fire at least a couple of seconds, which would indicate ( most of the time) the carb needed cleaning or rebuilding.Are there any other techniques that anyone can suggest I try?

I've adjusted the carb L and H about 1 to 2 turns counter-clockwise from their seated positions without any success. Are there any specific directions for setting the L and H adjustments for initial setting to get the engine started?

A search on the internet didn't reveal where I could get an owners manual for this chainsaw. Is one available anywhere?

I appreciate any feedback/comments.


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## paulr44 (Oct 14, 2008)

Will the spark jump a gap of about 0.150"?
What is the compression?
Does the plug get wet?


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## Dale1 (Nov 13, 2013)

paulr44, thanks for your response.

Compression is 100 psi.The plug gap when I tested it for spark was .025 inches, the recommended gap for running. I'll try it at .150 and see if I get a spark at that gap. 

I'll have to check again as to whether the plug gets wet. I assumed that fuel was getting to the cylinder since there *seemed *to be a damp or wet spot coming out the exhaust muffler after 20 or so pulls on the starter cord. I'll check the plug more carefully next time.


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## Dale1 (Nov 13, 2013)

Tried getting spark with plug gap at .060, the largest of my gauge capabilities. Essentially no spark ....plug would spark occassionlally if the starter rope pulled really fast, but pulling at what I'd call a normal pull rate resulted in no spark at all.

Re-gaping the plug to .035 give a pretty steady spark. I understand the recommended gap is .025. Engine didn't start or fire at .035 either. 

Checked the plug for wetness and it was wet.


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## paulr44 (Oct 14, 2008)

Ok, if you've read my other posts concerning diagnosis, you'll know. If not, then here it is again...for the spark to jump a plug gap of 0.025" UNDER COMPRESSION, you need A LOT more energy than to jump that same gap NOT UNDER compression.
In short, a spark plug IS NOT a SPARK TESTER. It does not impose a sufficient load to properly test the ignition system.

100 lbs. on pretty much any 2-stroke is insufficient. Most micro (25cc or less) require at least 120. Some of the box-store stuff may get by with less, but 120 is pretty much an industry standard.

Typically when a 2-stroke wets a plug but won't run, there can be several reasons I'll review.
1. Bad CC (crank-case) leak. The entire CC on a 2-stroke is part of the induction system, and must be airtight.
2. Scoring of the piston/cylinder, or major wear of either of those components.
3. No or weak spark.
4. Fuel system delivering copious amount of fuel (flooding out).
5. Engine is experiencing an erotic dream...wet dream, get it?

The air-fuel charge makes it's way up to the plug, but either it's way too rich (flooding), or it's too diluted (CC/vacuum leak), AND/OR insufficient compression for the system to work properly, may fart/sputter on occasion but not much else. OR OR OR, weak/no spark.

If spark/compression is ok, what I do is close off the mixture screws (or clamp fuel line) and keep cranking to see if it'll clear out and fire for a few seconds. If the carburetor is fine and a 2-stroke is flooded, usually clearing the cylinder and drying the plug, and then pulling over with choke and throttle wide open about 10 pulls will clear 'em out.

Mixture screw pre-sets vary greatly, but older units typically had pre-sets of 1 turn out.

Hope this helps...


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## paulr44 (Oct 14, 2008)

http://www.mcculloch.com/us/support/owners-manuals/


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## paulr44 (Oct 14, 2008)

P.S. I searched, and found what you're working on. Unless you have a lot of free time and money, ditch that thing and move on. Those were a grade-A headache to work on, and vibrated like crazy. And if memory serves, those have no automatic chain oiler system. RUN, don't walk awayyyyy!!!


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## Dale1 (Nov 13, 2013)

Thanks again paulr44. Your comments are very helpful. I'll keep you posted on any proegress.


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