fouling sparkplugs

Ok I have been riding my Honda ( 1966 C110 ) as much as I can lately. But after a half hour or so my spark plug is black. That is even with a new plug.

So what could it be?

I know my airfilter sucks and needs replacing badly

Carb is a little gummed up but not awful, doesn't like to idle but will run.

Could it be carbon build up in the exhaust?

My gas tank is super clean inside no rust.

I have compression, I have gas, and ussually have spark... so what is the fine tune for this ( non 2 cycle ) engine?

Re: fouling sparkplugs

Jason Luther /

its a 4 stroke? air filter would be my guess. try riding with it off for a while and see if its better. and what did you mean by usual spark (other than because of the fouled plug).-jason

Re: fouling sparkplugs

I tried without the air filter and had the same results. I soaked the air filter in gas.. same results.

And I meant ussualy have spark when they arent fouled I have spark.

I was thinking that the cylinder might be dirty and the combustion is knocking the crap around and the heat it adhering it to the plug.

I also added a little Marvelous Mystery Oil to the gas in hopes of cleaning th carb out some.. Could that have caused all this mess? If so i feel like a fool.

Re: fouling sparkplugs

sounds like the air filter, BUT you need to clean out that carb. take it off, clean it out well.

Re: fouling sparkplugs

anyone have any idea of where to get a new airfilter? I haven't found one or a part #

Re: fouling sparkplugs

Don Pflueger /

being an old honda mechanic, ive got some questions, and ideas, andanswers. first, how much compression do you have? 4 strokes should have about 75 lbs to run. second, how many miles are on this bike? third, does it smoke when it runs?

get the marvel mystery oil out of the tank. that will definetly cause plug fouling. as old as that bike is, and being a 4 stroke, the rings may be worn out. if so, it isdrawing the oil from thesump and burning it. a dirty air filter could be the problem. i dont remember if they are foam or not. i think they are and washing it in gas, and soap and water will clean itas good as new. the only time you really need to replace it is if it is disintergrating.

you can getall kinds of parts for this bike from

Re: fouling sparkplugs

ok I checked the site and they have almost every Honda ever made listed except my bike. Unfortunately the ones that are close matches use very different air filters.

I will take the gas out as soon as I get home and spray some carb cleaner in, and if needed remove and manually clean the carb out

Good thing I have another spark plug that isn't caked in crud.

As for how much compression I really don't know, I only did the good old fashioned finger method.

I am highly considering stripping the head and cleaning the cylinder, although I am concerned with the difficulty as it has push rods for the valves. I need to find a take apart diagram, head gasket and piston rings as I would like to do everything in one sitting.

But I will definitely start with emptying the gas out of it and replacing it with new gas.

Re: fouling sparkplugs

Don Pflueger /

there is adrain screw on your carb. lower right side if i remember correctly. you can buy foam air filter material from any bike, auto, or lawn mower repair parts stores and cut it to fit your bike. but as i said earlier, you can wash it if its not falling apart. valve clearances i believe are .006"-.008" on both valves. but i would want to double check a service manual. this guy may beable to help you with parts. i'm not sure how different is the c110 from a ct110. here again i would have to look at a service manual. i think your bike is a ko model. maybe thats what you need to look for on partsfish. <--this page lists theair filters for thec ct110. the owners name is jack and he's a cool guy. carries alot of old honda stuff.

Re: fouling sparkplugs

It has a completely different air filter than the ct110 but thanks for the link.

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