Tell me about this plug

[2broke2ride]

This came out of an old Mac 380 that I restored, I put new crank seals in but didn't touch the p&c. It shows 120psi on my compression gauge. I am struggling to tune it. I get a good fourstroke unloaded but it seems to not have much power in the cut. I pulled the plug and this is what it looks like......... Looks a little scary to me. The gray is a buildup almost like ash. I can't say that I've done much plug reading on a saw.... Always just tuned till it four strokes unloaded and clears up in the cut.

 

[backhoelover]

look like it getting to hot

 

[backhoelover]

check this out

 

[backhoelover]

also maybe to much mix

 

[2broke2ride]

I have that chart hanging on the wall in my garage lol, it doesn't look like any of them. It is almost like an ashy buildup. If I scrape it off with my fingernail it is a nice tan underneath. I was running some outboard premix instead of my normal oil because I had it laying around, maybe that's it. I have since switched back to my normal 32:1 I ran in all my 2-stroke equipment. I put a new plug in it tonight and I seem to have it running pretty good. Will keep an eye on the new one.

 

[HarleyT]

Too rich.

 

[grizz55chev]

120 compression is low.

 

[2broke2ride]

Too rich.

Might be, I'm still learning on the tuning thing. If I tune for max rpm "in the cut" it is a bit leaner then where I'm set right now but I don't get a noticeable 4 stroke unloaded but maybe that's ok for these old saws? Not really sure. I really wanna get it running good and I don't want to burn it down.

 

[2broke2ride]

120 compression is low.

I believe the manual for these oldies says anything over 100 is fine, I'll have to double check.
I think 150 is a "new" saw according to the manual.

 

[grizz55chev]

If it runs it must be ok, most saws won't run or hold a tune at that comp. if you are having a tough time running at idle that comp would be suspect. You could pull the muffler to be sure.

 

[2broke2ride]

If it runs it must be ok, most saws won't run or hold a tune at that comp. if you are having a tough time running at idle that comp would be suspect. You could pull the muffler to be sure.

It'll idle all day, starts 3 pulls cold, one or two hot.

 

[2broke2ride]

Right from the shop manual minimum compression is 90[emoji50]psi

 

[grizz55chev]

Run it! Better yet, trade it for a German saw, lol. Just kidding, seems you like the old iron and I can appreciate that. These old Macs can be a bugger to figure out, have some fun and learn something while you do, keep us posted.

 

[2broke2ride]

Bump to the top for marshy

 

[Marshy]

Put a new plug in your saw and give it some run time then check its color again. Without going into a lot of detail, you want to give it a fairly good amount of cutting time before you check it again and try to minimize idle time, especially when you go to shut it down and check the new plugs color.

 

[2broke2ride]

No time to mess with it tonight, just got home. I did put a new plug in it yesterday and I think I have it running pretty well. Although I'm still not sure I can hear it fourstrokeing, I tuned it to have good power in the cut.

 

[stihl041avhog]

look like it getting to hot

or not hot enough?

 

[Marshy]

Even though this isn't a chainsaw you get a good chance to hear the difference, just skip to 3:10 mark.


Here's a how-to on tuning. He shows you what to listen to.



Pay attention at the 8:00 mark. As he's cutting he lifts the saw a little while in the cut which takes the load off the saw and you can hear the saw 4stroke (burble) which is what you are shooting for.

 

[lone wolf]

It'll idle all day, starts 3 pulls cold, one or two hot.

Gauges are known to be wrong a lot.

 

[2broke2ride]

Gauges are known to be wrong a lot.

That's why I paid big money for a good name brand gauge instead of buying a harbor freight cheapie. As an auto technician, having quality tools is a necessity.