Reading A Used Spark Plug/ Update with Pics

[ScotO]

I generally don't worry too much about plug condition on small engines. It's seldom I pull out plugs that are "normal". The little engines are run hard and the carbs are simple and crude compared to even a 30 year old car's carb.

Really? I guess all those mechanics that say otherwise are wrong......sorry but I disagree. The condition of that plug tells everything, if you got a dirty carb, your engine isn't running to it's optimum.....

 

[thewoodlands]

I generally don't worry too much about plug condition on small engines. It's seldom I pull out plugs that are "normal". The little engines are run hard and the carbs are simple and crude compared to even a 30 year old car's carb.

Really? I guess all those mechanics that say otherwise are wrong......sorry but I disagree. The condition of that plug tells everything, if you got a dirty carb, your engine isn't running to it's optimum.....

Do you run regular unleaded for gas in your saws?

zap

 

[ScotO]

I generally don't worry too much about plug condition on small engines. It's seldom I pull out plugs that are "normal". The little engines are run hard and the carbs are simple and crude compared to even a 30 year old car's carb.

Really? I guess all those mechanics that say otherwise are wrong......sorry but I disagree. The condition of that plug tells everything, if you got a dirty carb, your engine isn't running to it's optimum.....

Do you run regular unleaded for gas in your saws?

zap

Zap, yes I do. I run 92 octane in them. I mix my gas with (drumroll please)......TCW3 oil. I don't care what anybody says, I have never had an issue and I have a PILE of hours on all my saws, most of the ones I use are 35+ years old and still kickin' ass. I run a 35:1 mix, saw is tuned to that mix. Never, ever had a failure either. Oh I foul the occasional plug, as when you run your saws alot (and I know you run yours quite a bit, too) like I do, you tend to run them with the filter clogged, sometimes forget to turn the "off" switch back to "on" before pulling it 4 or 5 times, cursing and swearing at it (been there, done that!) ,trying to start it when it's already warmed up with the choke button accidentally bumped "on" (that really pi$$es me of).... :lol: There are all kinds of variables in making that plug a little dirty. But the biggie is not tuning the carb to the mixture. When I run AvGas in it (occasionally), I have to lean it out a little. And it does scream with more power with the AvGas, but that gas is not totally necessary. I will say that when storing the saw for a really long time, you should run it dry (run all the gas out of it) or store it with AvGas throughout the system. Will be much easier to start, and will not get varnished in the carb like it will if it is stored with this modern junk pump gas in it.

 

[amateur cutter]

modern junk pump gas in it.???????

How can it be junk? They're gettin $4.00 a gallon around here lately. :bug:
BTW glad to here I'm not the only saw junkie around that re tunes regularly, do you tune for ambient temp also? A C

 

[ScotO]

modern junk pump gas in it.???????

How can it be junk? They're gettin $4.00 a gallon around here lately. :bug:
BTW glad to here I'm not the only saw junkie around that re tunes regularly, do you tune for ambient temp also? A C

yeah, tell me about it. With pump gas going upwards of six bucks this summer, wonder how much that AvGas is gonna be?? probably around 10 to 11 bucks a gallon....I usually tune it at the beginning of any job we do, just so it's purrin like a kitten......

 

[MasterMech]

Scotty,

That "antique" line-up probably doesn't mind the TCW-3 oils nearly as much as a modern day 14K+ rpm screamer would. None of them are from the 30wt days tho are they? I think even the 041's reccomend two-cycle specific oil.

 

[nate379]

,,

 

[nate379]

Exactly. Most carbs on small engines are quite crude in making correct a/f mixtures. Provided that the user constantly adjusts it for temp, altitude, humidity, etc I suppose it could run perfect.

Point I was making is don't stress out over a plug that isn't book definition of "normal"

There are all kinds of variables in making that plug a little dirty

t.[/quote]

 

[fyrwoodguy]

I'm curious what the plugs from saws running AvGas look like... Anybody got a pic?

here's a pic of a 357xpg that's being checked over after it's first tankfull of 100LL av gas and mobil 2t synthetic oil.
the arrow points to the automatic decopression valve.(that has a high failure rate)

 

[ScotO]

here's a pic of a 357xpg that's being checked over after it's first tankfull of 100LL av gas and mobil 2t synthetic oil.
the arrow points to the automatic decopression valve.(that has a high failure rate)

Went you your link, you have a nice shop there, Fyrewoodguy! I tinker on the side doing the chains, bars and tune-ups. I have a vintage Stihl collection that I use for cutting on the side. I'm not real familiar with the Husky saws, what's your take on that plug in your picture? Looks like theres some ash on it, and you said that's after one tank of AvGas?

 

[clemsonfor]

OK i have a stihl ms390. All this talk about frequent tuning makes me want to retune mine. I tuned it after a carb rebuild (that wasent necessary, another story) last year and dont remember the steps or the sounds im looking for. I think i need to bump my idle speed up a bit or lean out the mix at idle as it seems to idle low. I also think maybe you hold it wide open and tune the highspeed screw till it starts "2 stroking" or blubbering then back it back in a bit? Does this sound right? Jus tpost the correct stihl tune steps (i dotn have a tach).

 

[fyrwoodguy]

here's a pic of a 357xpg that's being checked over after it's first tankfull of 100LL av gas and mobil 2t synthetic oil.
the arrow points to the automatic decompression valve.(that has a high failure rate)

I'm not real familiar with the Husky saws, what's your take on that plug in your picture? Looks like theres some ash on it, and you said that's after one tank of AvGas?

good observation there,scott
there are 3 types of air filters available.one being a felt airfilter that gabs almost 100% of sawdust & dirt.is washable,but can't get all dirt out+felt goes away w/repeated cleaning.
and 2 that are nylon with 2 micron ratings-80. & 44. the 44 is pictured. i'm assuming the "ash" your referring too-is possibly wood ash that is passing thru the airfilter. the latter 2 are recommended for winter use,and the felt for dusty or summer use. here's that same plug after about 5 gal of av fuel used.

 

[ScotO]

Well the filter thing explains the ash I see. Tell you what, you got that saw tuned pretty nice now! Wish I was closer to your shop, I'd probably be the coffee/donuts guy on Saturday mornings! Great little business you got there, fyrewoodguy!

 

[MasterMech]

OK i have a stihl ms390. All this talk about frequent tuning makes me want to retune mine. I tuned it after a carb rebuild (that wasent necessary, another story) last year and dont remember the steps or the sounds im looking for. I think i need to bump my idle speed up a bit or lean out the mix at idle as it seems to idle low. I also think maybe you hold it wide open and tune the highspeed screw till it starts "2 stroking" or blubbering then back it back in a bit? Does this sound right? Jus tpost the correct stihl tune steps (i dotn have a tach).

Best thing for novice tuners is to get a tach, set it to factory specs and listen to what's going on. Then you can tune by ear once you know what you're listening to.

 

[ScotO]

OK i have a stihl ms390. All this talk about frequent tuning makes me want to retune mine. I tuned it after a carb rebuild (that wasent necessary, another story) last year and dont remember the steps or the sounds im looking for. I think i need to bump my idle speed up a bit or lean out the mix at idle as it seems to idle low. I also think maybe you hold it wide open and tune the highspeed screw till it starts "2 stroking" or blubbering then back it back in a bit? Does this sound right? Jus tpost the correct stihl tune steps (i dotn have a tach).

Best thing for novice tuners is to get a tach, set it to factory specs and listen to what's going on. Then you can tune by ear once you know what you're listening to.

that's a good point, MM.

 

[thewoodlands]

Is this the correct way to use the tachometer?

Place the chainsaw on a flat work bench.

2
Check to see if the spark plug wire is exposed. The spark plug wire is black and is connected to the spark plug. If its not exposed, remove the air filter cover located directly above the carburetor. This will expose the spark plug wire.

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Turn the tachometer into the on position. Wrap the external lead from the tachometer around the spark plug wire.

4
Start the engine and let it idle. Check the reading in the idle position. Most chainsaw operate between 2500 to 3000 RPM's. Check your model's service manual for the proper range.

5
Advance the throttle to the full throttle position. Check the reading. Normal RPM's in the full throttle position are between 11000 to 15000. Check your model's service manual for the correct operating range.


Swampy the Rookie

 

[MasterMech]

It depends on the specific model/type of tach but yes that's generally how it goes. Some are wireless. ;-)

 

[ScotO]

Is this the correct way to use the tachometer?

Place the chainsaw on a flat work bench.

2
Check to see if the spark plug wire is exposed. The spark plug wire is black and is connected to the spark plug. If its not exposed, remove the air filter cover located directly above the carburetor. This will expose the spark plug wire.

Sponsored Links


Turn the tachometer into the on position. Wrap the external lead from the tachometer around the spark plug wire.

4
Start the engine and let it idle. Check the reading in the idle position. Most chainsaw operate between 2500 to 3000 RPM's. Check your model's service manual for the proper range.

5
Advance the throttle to the full throttle position. Check the reading. Normal RPM's in the full throttle position are between 11000 to 15000. Check your model's service manual for the correct operating range.


Swampy the Rookie

that's about right, swampy. The pickup for the tach is a probe that reads out the firing pulses off of the plug wire. The way I do my saws is start the saw. Back off (very slowly) the low idle mix screw til the saw starts to rev. When you hear that revving it is starving for fuel, so advance it around a 1/4 then and check throttle response. For the full throttle you want to hold the saw wide open. You want to turn the hi-mix screw in either direction until the saw reaches full rpm. If you are richening the saw you want to go past the top of the rpm curve and turn the screw (while under full throttle) til the saw starts to "flutter" or "cycle". You want the saw to do that so you are getting good fuel/lubrication when cutting. When you plunge into wood and cut, the flutter will go away. With a little practice and patience you can learn to easily tune your saw on the fly. I've never used a tach before but I could see where it would help someone who has never tuned before as it takes the initial guesswork out of tuning. You'll eventually be able to do it by ear.

 

[thewoodlands]

I'l go back to 50-1 then just check the plug every so often. The plug I took out of the 660 Stihl was a NGK R BPMR7A, the plug they sold me is a Bosch R 10, is there a conversion chart out there.

zap

You CAN reuse your plugs, if you clean them properly (media blast), but you need to do it right. As for the plugs, NGK's are decent plugs but I pick Bosch HANDS-DOWN. That's all I use in my saws, period. As for your mix, I personally would run it at the 40:1, your saw will last longer. Just tune your high idle screw down to where the saw "flutters" a little at full throttle. Take it to a saw shop if you have to, trust me it's easy to do. Google it, maybe you can see how it is done on the 'net. Let me know how you make out. If I was closer I'd tune it for ya, bud.......

Tachs, are all the tachs the same quality or is one better than the other.

swampy

 

[MasterMech]

I'l go back to 50-1 then just check the plug every so often. The plug I took out of the 660 Stihl was a NGK R BPMR7A, the plug they sold me is a Bosch R 10, is there a conversion chart out there.

zap

You CAN reuse your plugs, if you clean them properly (media blast), but you need to do it right. As for the plugs, NGK's are decent plugs but I pick Bosch HANDS-DOWN. That's all I use in my saws, period. As for your mix, I personally would run it at the 40:1, your saw will last longer. Just tune your high idle screw down to where the saw "flutters" a little at full throttle. Take it to a saw shop if you have to, trust me it's easy to do. Google it, maybe you can see how it is done on the 'net. Let me know how you make out. If I was closer I'd tune it for ya, bud.......

Tachs, are all the tachs the same quality or is one better than the other.

swampy

Stihl's EDT Series is very good. Dunno who makes them for them. Refresh rate will be the make/break feature.

 

[ScotO]

Forgot to mention in my last post that after you find your idle mix and full throttle mix you will have to play with both screws to balance the carb. Also, remember do have they air filter cleaned out AND warm the saw up before you try and tune it. If you don't you'll be re-tuning it sooner than you think!

 

[thewoodlands]

I'l go back to 50-1 then just check the plug every so often. The plug I took out of the 660 Stihl was a NGK R BPMR7A, the plug they sold me is a Bosch R 10, is there a conversion chart out there.

zap

You CAN reuse your plugs, if you clean them properly (media blast), but you need to do it right. As for the plugs, NGK's are decent plugs but I pick Bosch HANDS-DOWN. That's all I use in my saws, period. As for your mix, I personally would run it at the 40:1, your saw will last longer. Just tune your high idle screw down to where the saw "flutters" a little at full throttle. Take it to a saw shop if you have to, trust me it's easy to do. Google it, maybe you can see how it is done on the 'net. Let me know how you make out. If I was closer I'd tune it for ya, bud.......

Tachs, are all the tachs the same quality or is one better than the other.

swampy

Stihl's EDT Series is very good. Dunno who makes them for them. Refresh rate will be the make/break feature.

I just ordered through our local dealer the EDT7, should be in next week.

Thanks
Swampy

 

[thewoodlands]

Stihl's EDT Series is very good. Dunno who makes them for them. Refresh rate will be the make/break feature.

Just received a call from our local Stihl dealer, the Tach I ordered is in so I'll pick it up Monday morning.

Swampy

 

[MasterMech]

Suhweeet! Off to tuning nirvana you go!

 

[thewoodlands]

Suhweeet! Off to tuning nirvana you go!

I'll do the 310 first, the low idle was off some before I adjusted it. Starting tomorrow the pine is coming out of the woods to be stacked, once that is done I might start milling.

swampy