SuzukiSavage.com - Spark Plug help

Yellow96 Junior Member Offline Posts: 67	Spark Plug help 06/08/07 at 13:05:02 I have a modified bike that seems to always run lean at idle even though my edelbrock carb is tuned all the way rich. A guy I know asked me if I had considered a different spark plug to solve the problem. Anyone ever try that? Not sure what the thought is behind it, looking for ideas.
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Savage_Rob Serious Thumper Alliance Member Offline Mechanically Inclined Amateur Posts: 6972 Texas (Dallas area) Gender:	Re: Spark Plug help Reply #1 - 06/08/07 at 13:17:52 If your talking idle only, have you changed your pilot jet size? Can you increase it?
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Yellow96 Junior Member Offline Posts: 67	Re: Spark Plug help Reply #2 - 06/08/07 at 14:19:33 The edelbrock doesnt have a pilot jet. it's a flat slide with an adjustment knob to run it leaner or richer by drawing out the needle or running it deeper in the slide. kinda cool set up unless it doesn't go far enough.
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BornOnFire

Ex Member

Re: Spark Plug help
Reply #3 - 06/08/07 at 17:17:52

I think what he was implying is what controls the pilot circuit on that carb? Is it a needle with an adjustable clip under the diaphram or something? Maybe it needs to be moved up a notch. Sounds like a pilot issue to me as well, but I don't know if a hotter plug will solve that. Nonetheless, it's a cheap remedy to at least try out. I'd be curious to know if it helps you out at all.

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thumperclone Serious Thumper Alliance Member Offline PGR rider riding with respect Posts: 6044 Grand Junction Colorado Gender:	Re: Spark Plug help Reply #4 - 06/08/07 at 17:21:25 is the plug wet???
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Yellow96

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Re: Spark Plug help
Reply #5 - 06/08/07 at 21:02:54

Right, On the edelbrock the pilot part is controlled with a knob that can be adjusted by shutting the bike off, rolling on the throttle and twisting the knob right for rich and left for lean (controls idle to 1/3 throttle). The rest of the mixture is set by the needle size. I have the idle mixture set at full rich and it still backfires after I shut it off.

I am running a new stock NGK. What plug do you recommend? I don't have much background here.

Not sure what you mean thumperclone, is the plug wet? Do you mean gas soaked?

The strange thing about this is that the full open part of the needle is too rich. I have tried other needles but havent had any luck, I have one more size to try. Good that they aren't too expensive.

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Savage_Rob Serious Thumper Alliance Member Offline Mechanically Inclined Amateur Posts: 6972 Texas (Dallas area) Gender:	Re: Spark Plug help Reply #6 - 06/10/07 at 09:34:11 Ahh, I completely missed that you said it was an Edelbrock. I've never used one though I've considered it as I'm generally a fan of simplicity. I believe Lancer has some experience with them. If he doesn't see this thread anytime soon, you might try sending him an email or a PM.
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Yellow96 Junior Member Offline Posts: 67	Re: Spark Plug help Reply #7 - 06/10/07 at 17:59:59 So can someone help with how to pick a hotter/cooler plug? Which one makes it richer. How does that work? What number plug should I try?
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justin_o_guy Ex Member	Re: Spark Plug help Reply #8 - 06/10/07 at 19:37:25 I step gingerly onto the limb. I would guess I would go with a cooler plug if I was lean & a hotter plug if I was rich.
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Reelthing Serious Thumper Alliance Member Offline Fish or ride that is the question Posts: 5397 Houston,Tx Gender:	Re: Spark Plug help Reply #9 - 06/10/07 at 20:59:11 Yellow96 wrote on 12/31/69 at 16:00:06: So can someone help with how to pick a hotter/cooler plug? Which one makes it richer. How does that work? What number plug should I try? ??? which sparkplug will change the mixture ???
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justin_o_guy

Ex Member

Re: Spark Plug help
Reply #10 - 06/11/07 at 05:04:21

I know a plug wont actually change the mix, but IF I am lean, then I wouldnt want a hot plug, too. Right? Or would it matter to the piston at all? Once a lean mix fires, its hot in there. If it's gonna hole the piston, no cooler plug will stop it, I'll be betting.
But, if I am rich, then shouldnt I be running a hotter plug?

I know the real answer is to get the jetting right, but that wassnt the question.

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Yellow96

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Re: Spark Plug help
Reply #11 - 06/11/07 at 06:13:21

Exactly what I hope to learn Justin. If I run a cooler plug for a lean condition, then what I'm doing is trying to have an incomplete burn in the cylinder, right? I know its not the right way to solve the problem, but the guy who put this edelbrock on (long ago and a few owners back) probably used the wrong one and I really don't want to drop carb money in this bike.

If I run a cooler plug though, won't it effect the burn at all rpms? That would be a problem since the carb runs a little rich from 1/3 to open throttle. I could fix that with a new needle, which is pretty cheap.

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barry68v10

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Re: Spark Plug help
Reply #12 - 06/11/07 at 07:39:21

Ok, I'll wade in here now...

A cooler plug or a smaller spark gap will cause a lean engine to act "richer." The reason is the burn will happen slower, especially a smaller spark gap which will act like retarded timing, and basically has the same effect. If you're running too rich at WOT, then either of these "fixes" will make your WOT problem worse and much more pronounced.

Hope this helps. BTW, what exhaust are you running? Stock backpressure will greatly simplify tuning, and cover a multitude of "tuning sins" Grin

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petc0ck mod, white spacer removed, 150 main jet, 12.5" shocks, 16" turnout muff, oil cooler mod, chain conversion, Tkat brace, external fuel filter, fuel screen removed...

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Yellow96 Junior Member Offline Posts: 67	Re: Spark Plug help Reply #13 - 06/11/07 at 14:55:22 I have the Dyna muff and the drop-in K&N, Lots of flow on the bike and that carb is pretty free flowing.
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barry68v10

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Re: Spark Plug help
Reply #14 - 06/11/07 at 16:56:26

Ok, that's not that radical. You may not like the unintended consequences of completely eliminating "backfires after I shut it off." You may experience poor "hot weather" performance and greatly reduced MPG. Backfire, or more accurately "post ignition" is part and parcel with an efficiently tuned single. My bike gives a modest "poof" on shutdown and is turning in just under 70 MPG on the highway.

You might try 1 heat range cooler plug, or decreased spark plug gap of .005-.007 inches, and see how you like it.

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petc0ck mod, white spacer removed, 150 main jet, 12.5" shocks, 16" turnout muff, oil cooler mod, chain conversion, Tkat brace, external fuel filter, fuel screen removed...

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