Author Topic: Plug Reading (Read 12194 times)

Pricecheck · « **on:** February 17, 2014, 09:27:41 PM »

Here's what I have going on. It was about 45* 1,100' elevation out today and I decided to finally do some plug chops. I did the normal warm up and the whole sequence that is called for. I'm running 32:1 VP C12/Castor 927 mix, 39mm PWK, 330 +4 stroker and an 01 cr250 ignition. No advancements or retarding of timing. Also running a B8es plug gapped at .018.

My first setup today was dgh 2nd clip, 50 pilot and 185 main. It looked like the pictures below but lacked the blackish ring the whole way around the plug top (whatever that is called). It was a chocolate color but only near the strap.

The pics below are from my adjustment run of dgh 2nd clip, 50 pilot and 188 main. As you see, the top area is a uniform color the whole way around. Both runs resulted in the electrode being barely brown and the strap anneal line being near the base.

I'm trying to understand how I can get that nice paper bag/chocolate brown shade to the electrode and that nice anneal line around the bend of the strap. B9 series plug? Increase the gap? Retard or advance timing?

Note: It does feel very slightly lazy on the top end. I know it wants to pull more but it just doesn't seem to be all the way there. It does move out but just seems ever so slightly flat up top. Maybe I'm just expecting more since I love going fast!

Please help. I know there are hundreds of threads on this stuff but I'm just trying to find a solid answer quickly.

fearlessfred · « **Reply #1 on:** February 17, 2014, 11:32:34 PM »

I have read that you can read the plug by looking at the soot around the ground base ,most people cut the treaded part off and look at how high the ring comes up the porcelain,'i believe it should be 2 mm high,as far as the tan color goes,jt will happen with time on the plug but isn't used to read it,try a 9 and see if the blueing moves to the midway point.most 250r guy believe that .018 is the way to go but I only think so if it is needed because of misfire

Pricecheck · « **Reply #2 on:** February 17, 2014, 11:48:20 PM »

I was recommended an 8 series but I might try some 9 series to see what it does. Everywhere I'm reading says that my plug is too hot. I know my idle is rich as well. I'm getting plenty of smoke, almost too much. If I ride normal my plug gets a black coating all over everything but no clumps of anything. Just rich. I'm already running a 50 pilot but I think I might double check my air/fuel mixture once I get this plug thing fixed. Overall it pulls great across the board so it might be safe to keep it rich down low to mid since I run in that range.

By the way, thank you for responding!

fearlessfred · « **Reply #3 on:** February 18, 2014, 12:17:27 AM »

you should probably start with the slow jet,move to the needle and then main.I really don't think you get a good main reading when the motors trying to clean out all the extra fuel

mx250r91 · « **Reply #4 on:** February 18, 2014, 08:22:55 AM »

Sounds like you are on the right path:

Be careful with a 'G' length needle, it is pretty lean in the midrange. Going with a 'D' or 'E' length (DDH, DEH) might help darken up the plug. See if you can cut the threads off to see the fuel ring at the base of the plug.

Jerry Hall · « **Reply #5 on:** February 18, 2014, 11:19:09 AM »

I am see a large number of customers burning pistons as a result of following published misinformation about reading spark plugs. There are some beliefs that are wrong and becoming very popular on the internet. A spark plug is NOT an device that can read air fuel ratio. An O2 sensor will not accurately read air fuel ratios from a high performance two stroke engine. I would like to dispel some of the misunderstanding that laymen have about reading spark plugs. I do not want to offend those that have taken considerable time to publish/pass on this information unless the members here want me to pass on some of my experiences with tuning engines and reading spark plugs.

havinnoj · « **Reply #6 on:** February 18, 2014, 11:24:50 AM »

Quote from: Jerry Hall;25942

I am see a large number of customers burning pistons as a result of following published misinformation about reading spark plugs. There are some beliefs that are wrong and becoming very popular on the internet. A spark plug is NOT an device that can read air fuel ratio. An O2 sensor will not accurately read air fuel ratios from a high performance two stroke engine. I would like to dispel some of the misunderstanding that laymen have about reading spark plugs. I do not want to offend those that have taken considerable time to publish/pass on this information unless the members here want me to pass on some of my experiences with tuning engines and reading spark plugs.

By all means Jerry.. please post your insight.

Mr250sx · « **Reply #7 on:** February 18, 2014, 11:26:14 AM »

I'd like to hear Jerry's expert opinion and technical advice on plug reading for sure..

rsss396 · « **Reply #8 on:** February 18, 2014, 12:35:17 PM »

always good to hear the experience of others, please share Jerry

rsss396 · « **Reply #9 on:** February 18, 2014, 12:42:42 PM »

The way I read plugs for gas is to read the insulator ring like shown in the picture, but the strap reading has not been very consistent IMO on gasoline

For alcohol I look at the flat surface of the plug exposed to the combustion chamber and look for about half of this surface to have the zinc plating to be discolored

fearlessfred · « **Reply #10 on:** February 18, 2014, 06:51:52 PM »

Jerry, please share

mwiley · « **Reply #11 on:** February 20, 2014, 07:13:44 PM »

I would also like to hear Mr. Hall's thoughts on the Gordon Jennings 2-stroke articles/book.

Pricecheck · « **Reply #12 on:** February 20, 2014, 08:56:00 PM »

Jerry, please inform us.

As of now I picked up eight B8ES plugs to try out. I might just have to pick up a new needle. If not for use, at least to try out and/or have options. I've actually heard that the dgh needle could never be fine tuned easily with my engine. Maybe this was for people who wanted peak hp in every bit of the throttle. Do I want this? Hell yes I do! I would just rather be running just a little rich to be safe. Tomorrow I'll be working the chops again to see what they yield.

Jerry, to give an update here's what I'll have tomorrow to work with: 330 stroker, 39PWK (50 pilot, 188 main, 1 1/4 turns air/fuel, 3 1/2 slide screw, dgh 2nd clip), TRX5 pipe and silencer, k&n with outerwears in lidless stock box, 32:1 VP C12/Castor 927, 01 CR250 ignition no advance/retard, and riding in Kansas weather at 1,100' altitude and about 45*-50* weather. Misc crap that affect cooling and drag.... pwk radiator, 14/36 gears, o-ring chain, 20" rears. I know it isn't needed but it's what is going on.

Allison#51 · « **Reply #13 on:** February 20, 2014, 09:11:19 PM »

I would also like to be informed! I'm very curious about this stuff.

Pricecheck · « **Reply #14 on:** February 21, 2014, 05:13:17 PM »

Here's a quick two WOT runs with the 9-series plug. No jetting or needle changes....

You can ever so slightly see the line on the strap. Down at the base of the ceramic I could see what looked to be a couple millimeters of darkness. You can see that the ring is covered at about 3/4 of it. The top of the electrode will still not get any darker.