Reading A Used Spark Plug/ Update with Pics

[thewoodlands]

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

Since I'm changing the spark plugs on the Stihl Chainsaws I thought this was appropriate.

zap

 

[smokinj]

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

Since I'm changing the spark plugs on the Stihl Chainsaws I thought this was appropriate.

zap

Good stuff!

 

[thewoodlands]

I take a quick look when taking them out but will pay more attention to what they are saying, the 310 & 390 will get changed tonight then I'll throw the pics up of the old spark plugs.

Zap

 

[ScotO]

Great info there, Zap. When I tune or rebuild a saw, I use the spark plug as one way to get the saw tuned properly. Everybody that does serious firewood cutting or logging should know how to watch their spark plug and tune their saw. Thanks for sharing!

 

[Bocefus78]

Good info for sure! I just got done giving the local shop almost $55 for those stupid bosch plugs for all my stihl stuff I clean and keep the old ones as spares in case of failure on a job.

 

[HittinSteel]

Good info for sure! I just got done giving the local shop almost $55 for those stupid bosch plugs for all my stihl stuff I clean and keep the old ones as spares in case of failure on a job.

Yikes, I'd be scared to death to see the mark up by stihl for a sparkplug........here's a cross reference list if you want to tell your dealer to take a flying leap.


http://www.angelfire.com/extreme4/skidoolympique/SPARK_PLUG_CROSS_REFERENCE.htm

 

[thewoodlands]

Good info for sure! I just got done giving the local shop almost $55 for those stupid bosch plugs for all my stihl stuff I clean and keep the old ones as spares in case of failure on a job.

Just bought three Bosch plugs for the saws from our local Stihl dealer, cost was $5.00 plus tax.


zap

 

[smokinj]

Good info for sure! I just got done giving the local shop almost $55 for those stupid bosch plugs for all my stihl stuff I clean and keep the old ones as spares in case of failure on a job.

Just bought three Bosch plugs for the saws from our local Stihl dealer, cost was $5.00 plus tax.


zap

Yea, but he got those ones that gives it extra horse power! :lol: So 10.00 a plug and you can add another 7 percent to the bottom line. ;-)

 

[ScotO]

Good info for sure! I just got done giving the local shop almost $55 for those stupid bosch plugs for all my stihl stuff I clean and keep the old ones as spares in case of failure on a job.

Just bought three Bosch plugs for the saws from our local Stihl dealer, cost was $5.00 plus tax.


zap

Yea, but he got those ones that gives it extra horse power! :lol: So 10.00 a plug and you can add another 7 percent to the bottom line. ;-)

a 40% power increase fer sure Who needs porting! Lol....

 

[firebroad]

WoW! What a great list of info. I am going to print that out.

$55 spark plugs?! And to think I yelped at $7...

 

[backpack09]

I always end up with yellow tips on my plugs.... All that leaded race gas I use.

 

[thewoodlands]

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

Since I'm changing the spark plugs on the Stihl Chainsaws I thought this was appropriate.

zap

Good stuff!

Pic 4744 is the plug from the 660 and pic 4745 is the plug from the 390.

The spark plug in the 310 was new,the plug from the 390 is the one on the right in picture 4742 and the 660 plug was horrible. Mixing 50-1, the 660 plug was in for all the milling. Is the 660 plug dry & wet fouling or running hot?

zap

 

[ScotO]

That 660 plug looks like it is being run a little rich, leading to dry fouling. I am assuming you keep it running at high throttle, being you are milling with it. When you adjust your high throttle screw, is that being done with the air filter cleaned out and installed on the saw? Sometimes a clogged up air filter can cause your plug to get like that too! Looking at that plug that's what I would say is going on. Just a hair too rich...hold 'er at full throttle, tune the high screw down a little and that should clear it up...

 

[thewoodlands]

I posted that my mixture was 50-1, but when I stopped by our local Stihl dealer in late fall he mentioned I would be better off mixing 40-1 so I had about 4 gallons mixed that way, would that cause that?

zap

 

[ScotO]

I posted that my mixture was 50-1, but when I stopped by our local Stihl dealer in late fall he mentioned I would be better off mixing 40-1 so I had about 4 gallons mixed that way, would that cause that?

zap

That could lead to that, absolutely. When you adjust your oil/fuel ratio, or even changing from one octane to another (or from pump gas to AvGas) you will need to tune your saw to run with the changed mix.

 

[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

 

[ScotO]

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.......

 

[Hogwildz]

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.......

I'm close, when do I get my tuneup? LOL

 

[ScotO]

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.......

I'm close, when do I get my tuneup? LOL

Bring 'er on over and we'll tune it up bro. Heck, while we're at it, we'll clearcut some of the mountain behind the house!! ;-)

 

[ScotO]

Zap, here is one cross-reference chart I found. This isn't all of the saws out there, but this does have some cross-references for many plugs still used today.

http://www.acresinternet.com/cscc.n...e39d1995d7ddc91588256e0c00029d0f?OpenDocument

 

[MasterMech]

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

 

[wkpoor]

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

I've taken pics in the past but don't have any handy right now. They stay pretty darn clean on AvGas which is all I run in all my 2 cycle hand held stuff. I also run it in my Farmall H that has 225 lbs cranking compression. They stay spotless clean in that machine. I would say they have more of a bone color than tan like pump gas.

 

[Hogwildz]

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.......

I'm close, when do I get my tuneup? LOL

Bring 'er on over and we'll tune it up bro. Heck, while we're at it, we'll clearcut some of the mountain behind the house!! ;-)

You gimme the directions, I'll be there.

 

[ScotO]

You gimme the directions, I'll be there.

I'm between State College and Altoona. My one buddy used to work at the Nuke Plant up there in Berwick!!

 

[nate379]

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.