I wont go by spark plug as guide anymore!!!!

I have done as many if not most by checking the fuel air mixture by looking at the spark plug after doing a speed run and shutting down etc etc....

Well there are much more accurate ways to check you setup and I was lucky enough to do that yesterday after being told over and over again that my plugs showed a critical lean condition.

I went to a race car builders shop and he welded a sensor bung after the collector of my 4 into 1 exhaust, best welding I have ever seen by the way, and he hooked up his fuel air mixture prob and portable computer to my bike and took it out for an extensive set of tests at all speeds including red line shifts through 4th gear. Here is what he found:

(perfect fuel air mixture for a gas engine without any boost like a turbo should be in the 13.5 to 1 area. He ops for a slight rich burn in the 12.5-13 range for most situations.

Red line full throttle 12.8 to 1
Cruising 12.6 to 1
Low speed 13.1 to 1
Idle 19.1 to 1 (Very Lean at Idle)

He adjusted the idle mixture screw to get a 12.3 to 1 ratio. he recommends a hair richer to stop take off hesitation as the fuel circuits open up.

My plus look like this, see picture. That was a 65mph 8-10 mile run hitting kill switch and coasting to a stop to read plug so the idle circuit lean condition was not any affect on the burn read.

The mechanic also said that trying to read the mixture through plug reading is accurate at all. I have to agree after seeing this.

Now I know people have done it this way forever, as have I but in my opinion you can't trust a spark plug to tell you the truth.

Now for the backlash

 

Re: Wont go by spark plug as guide anymore!!!!

No backlash here, I have 2 FI bikes and they look like that and thats what a modern cars plugs look like. I'm thinking the brown color was from the days of lead and no ethinol

 

Re: Wont go by spark plug as guide anymore!!!!

None here either, but it would be nice to have a sensor on each downpipe so you know the mix of each pot since they are individually set. Logically you would probably need to block the YICS channel to get a totally accurate read even then.

I've used the plug method but have always opted for the almost white state since I prefer the mpg and less pollution. Also although unscientific, if you are blowing smoke out of your mufflers upon heavy acceleration after warm up, then that's pretty rich. One other thing is most plugs are read wrong, you can't go by the end of the insulator, you need to look down the insulator where it meets the plug body.

 

Re: Wont go by spark plug as guide anymore!!!!

I put 4 screws in my kerker header 4 into one at the bottom of each down tube just before the collector . My mechanic used them to tune my bike . It worked great just like the stock testing method .

 

Re: Wont go by spark plug as guide anymore!!!!

i tried to put a wideband O2 sensor in my muffler once and read it with a meter, it was a miserable failure

 

Re: Wont go by spark plug as guide anymore!!!!

Dano59, Cool info. Do the rest of the plugs look the same as the one you posted?

Polock, Spill it... What happened with the backyard wideband attempt?

 

Re: Wont go by spark plug as guide anymore!!!!

You need to take into consideration that the Bike has a High-revving, AIR-cooled, ALUMINUM Plant.

Even if the Bike was Liquid-cooled, ... a Plug that clean means you are running too Lean.

If the BURN is too Lean because you believe the results of a "Sniff-Test" and disregard the Tried-and-true Method of Reading the Plugs, ... you are quite possibly setting yourself up for welding a hole right through the top of a Piston Crown.

We're trying to help you prevent a catastrophe!

Please, ... don't try to tell us that we are wasting our time reading our Plugs.
I think you will find that there are a great many of us who rely on what our Plugs have to say about how well our bikes are performing.

That Plug in your photo indicates that you are running too Lean.
I think there are others who will say so, ... too!

 

Re: Wont go by spark plug as guide anymore!!!!

i used a heated wideband sensor a battery and a digital meter, the meter was all over the place, like off the scale rich to off the scale lean, never even trying to settle. i turned the mixture screws 1/2 turn in and 1/2 turn out, no effect......?
thought my setup was bad so i stuck it in my kia with only a few thousand miles and it was rock steady where it should have been. then in my ranger with over 100k and it was steady within a point or two.
it's in a box on a shelf somewhere now

 

Re: Wont go by spark plug as guide anymore!!!!

Not messing with a good idea either - but - -

If your exhaust gaskets were even slightly leaky -
You would get a high idle reading, and it's gonna mess up your thinking about all this. 19.1 is on the hairy edge of not burning.

You would need to pressurize your exhaust with white smoke in it, and see if it puffs out at the head.
If any of the 4 gaskets leak - exhaust puffs out and pure air puffs in.

 

Re: Wont go by spark plug as guide anymore!!!!

Well RickCoMatic,
First I never tols anyone to not read the plugs. I in fact said that many if not most have beenrreading plugs forever as I have.

Secondly I never said you were waisting your time reading plugs. I only reported what I found and what has happen in the testing I did to check my setup.

Please, ........Don't try and tell me not to share information gained through sound mechanical testing by an ASE Certified mecanic and a builder of both top fuel race engines and drag motocycles. He has also tunned and set up 6 motocycles the same way (that I personally know) over the past couple years who have put thousands of miles on all of them.

If I am wrong in trusting a more scientific way of testing for proper air fuel mixture and end up melting a piston or other failure I will be the first one to say so but until then I will shsre the process I have gone through snd let people make there own choices. After all that is what this forum is all about, right?

 

Re: Wont go by spark plug as guide anymore!!!!

The reading works good on a car because you only have 1 carb for multiple
cyls you really need 1 for each cyl you could have 1 running much leaner then the others. . It really takes a while with the new gas to get any color at all unless your way rich. Ethanol keeps everything spotless cleans great just really bad for motorcycles and small engines. Check tour plugs really well if you have any little specs on the electrode insulator that is aluminum melting.
If you can find a station without ethanol fill it up then try your test chops again you will have more color

 

Re: Wont go by spark plug as guide anymore!!!!

Yes agreed thst 19.1 in almost off thr readable range of the tool also that is why it was corrected buy backing out the idle mixture screws a touch at a time until set properly.

 

Re: Wont go by spark plug as guide anymore!!!!

Yes you correct that the best situation would be a four channel set up but that is why everything was gone through from valves and complete rebuild of carbs, bench sync etc etc new plugs air cleaner before testing done. Obviously the idle mixture screws were not set correctly and the screws were kept equaly adjusted.

Thanks

 

Re: Wont go by spark plug as guide anymore!!!!

This is Rick's major point that is unwise to ignore. Water cooled and large displacement motors have a much larger margin of error when it comes to cooling. Rick knows this from mucho experience I can assure you. Even though I prefer to lean towards lean (forgive the pun), I respect his advice and experience immensely, as he is one of the major reasons my bike is in top tune.

If you aren't absolutely sure about your motors mix or you ride long or hard EVER then you should play it safe and lean towards rich-I constantly monitor my temp, oil, and other signs for any issues and honestly if I was going to hit the road for a cross-country trip I would crank my screws out about 10-20minutes worth to add some cool. It would be a shame to melt a classic.

This is in no way a flame, but honestly Dano your threads title does suggest that one shouldn't check plugs and your second to last sentence in your first post also suggests that it's a waste of time. Still a worthy topic and important subject for longevity for sure.

 

Re: Wont go by spark plug as guide anymore!!!!

This is Rick's major point that is unwise to ignore. Water cooled and large displacement motors have a much larger margin of error when it comes to cooling. Rick knows this from mucho experience I can assure you. Even though I prefer to lean towards lean (forgive the pun), I respect his advice and experience immensely, as he is one of the major reasons my bike is in top tune.

If you aren't absolutely sure about your motors mix or you ride long or hard EVER then you should play it safe and lean towards rich-I constantly monitor my temp, oil, and other signs for any issues and honestly if I was going to hit the road for a cross-country trip I would crank my screws out about 10-20minutes worth to add some cool. It would be a shame to melt a classic.

This is in no way a flame, but honestly Dano your threads title does suggest that one shouldn't check plugs and your second to last sentence in your first post also suggests that it's a waste of time. Still a worthy topic and important subject for longevity for sure.[/quote]

Thanks for the input. I changed the heading to include "I Wont" as that was my intention by saying Wont.

 

Re: Wont go by spark plug as guide anymore!!!!

Thanks Polock

Huh. Interesting. Sounds like the concept was fine but it just didn't work on the bike for some reason.

Wonder if you were lean misfiring... Would indicate lean when firing and rich on a miss. Maybe a full turn rich would have smoothed it out.

Cool and imaginative in any event. :idea: