'70 rude 25 plugs fouling

[reka12]

All: I have done a lot of work (head gasket, carb, impeller) on this motor but am still having a problem. When running a while in the trash can (full throttle in nuetral) one of the plugs fouls. I can clean it (both) and it will run fine, with throttle for a few minutes. It will foul again. The plugs are B8S NGKs. Is this the right plug? Can I get a "hotter" plug? She seems to run cool.<br /><br />On another note, I have not been able to find a good idle setting. There is only one adjustment, the slow idle screw. I seat it and back it out one turn. Attach the linkage to the adjustment knob. It still wants to backfire and stall. I am not sure that this is unrelated to the above problem or not.<br /><br />Finally, the motor does not have a kill switch. The idle speed adjustment screw near the tiller handle gear is out far enough that it does not touch. To shut off the motor, I turn the throttle all the way till it quits. I noticed that there are two black wires with connectors near the neutral starter safety switch and wonder if they were for a kill button.<br /><br />It is an electric start model.<br /><br />Thanks for your help.

 

[reka12]

Re: '70 rude 25 plugs fouling

One more note, I was able to check the compression: 125 on both! The head gasket replacement did the trick.

 

[Paul Moir]

Re: '70 rude 25 plugs fouling

B8S is not the right plug at all. It is far too cold for your engine, and that's likely causing your fouling problems. Stop using NGK altogether and use the Champion J4C that was originally specified for your engine. Gap should be .030"<br />Hotter or cooler plugs have little to do with the operating temperature of the engine. It has more to do with engine design. <br />If you're not talking about Johnson/Evinrude engines, I'm no fan of Champion over another plug. But they were designed with these plugs, and they do work better with them.<br /><br />It sounds like your engine was once set up for remote operation. Those two black wires are likely for the kill switch then. If they are, they'll ultimately lead up to the armature plate underneath the flywheel. To stop the engine, try connecting them together. <br /><br />Hope this helps!

 

[reka12]

Re: '70 rude 25 plugs fouling

Thanks Paul (once more!) I'll give the J4Cs a try. I got the B8S from the following: http://www.maxrules.com/fixomctunekits.html . He uses the NGK B8s on his tuneup kits for this motor.

 

[Paul Moir]

Re: '70 rude 25 plugs fouling

That is strange. Even the NGK cross-reference tells me that it ought to have a B6S (lower numbers are hotter).<br /><br />Oh, and I'm sorry I never responded to your last post. I was away from the computer for some time. But it was good to hear you got it up and running!

 

[reka12]

Re: '70 rude 25 plugs fouling

Well, thanks and I will let you know how it goes. Mike

 

[JB]

Re: '70 rude 25 plugs fouling

Hi, Reka.<br /><br />Running any 2 stroke at full throttle with no load is a dangerous practice. Thermal runaway is possible and usually results in something breaking.<br /><br />Keep the engine below about 2500rpm with no load.<br /><br />Good luck.

 

[Chinewalker]

Re: '70 rude 25 plugs fouling

Just a personal preference - I run Champion J6Cs in my older 2-banger OMCs. They seem to like a little extra heat in the plugs with today's fuels. They burn a nice light chocolate in color and seem to make for easier starting... Again, this is just my preference. You will not hurt your motor using either plug (the J4C or J6C) and you can experiment if you wish without harming the motor...<br />- Scott

 

[reka12]

Re: '70 rude 25 plugs fouling

Thank you all. I will keep you posted!

 

[reka12]

Re: '70 rude 25 plugs fouling

FYI: See the link below from Champion. For NGK, Lower is hotter. For Champion, Higher is hotter. The '70 service manual says that Champion J4J is the correct plug. Since lower is cooler for Champion, this would seem to be a cooler plug. Of course this engine is 25 years old and may need a little oomph. I think I will give the J6C's a try tomorrow. <br /><br />By the way, has anyone have experience with it common to have leaf valve go bad on these motors? It seems to be a part that could go bad but have not found the part readily available.

 

[reka12]

Re: '70 rude 25 plugs fouling

Forgot Link: http://www.championsparkplugs.com/faqmain.asp

 

[Paul Moir]

Re: '70 rude 25 plugs fouling

It is very, very rare to have a reed go on OMC outboards of this era. That's why you don't see them offered everywhere. The dealer should be able to get you them if you need one though.<br /><br />I would be inclined to follow Chinewalker's suggetion on the J6C. It was the hotter option plug back in the day (J8C is too hot), and between todays fuels and the likely less-than-ideal compression on your engine, it makes good sense. Heat range essentially means ability to burn off carbon build up, so it doesn't add any 'oomph' to the engine. As far as I can cross it, the B8S would end up somewhere around a J3C, maybe less.

 

[reka12]

Re: '70 rude 25 plugs fouling

I got the same thing. Interesting, the book at Advance cross referenced both teh Champion J6C and J8C to the NGK B6S. I guess there are no absolutes to plugs. I also understand that the plugs will not give you more "oomp" as in hp, but a genralization to a little more plug electrode temp to minimize fouling. Kinda like plugs, no realy quantification to the description "oomph". I'll try to be be more technical on the description. B'sides, I think we may have beat this horse enough.

 

[Paul Moir]

Re: '70 rude 25 plugs fouling

Gotcha! You know how people are with spark plugs though.

 

[reka12]

Re: '70 rude 25 plugs fouling

Did not think that I would be revisiting this one. Just got back from Ace. The Champion book listed the J8C as the plug for my motor. Moral of this story? Read the plugs. I think that would be more accurate than all the conflicting liturature out there!