Spark plug fouling repeatedly - LTZ 400
 

Howdy- I'm trying to figure out why the spark plug on my 2004 Suzuki LTZ 400 has begun fouling.

I had the quad in the shop a few weeks ago, and they replaced the plug and explained that the spark plug was fouled. Great, it was back running tip-top.

I rode last week each day Monday through Saturday. Then, Saturday afternoon, it wouldn't start. Upon removing the plug, we found that the new plug was fouled -- all carbon-ed up. What's up w/ that?

The machine is stock except for some nerfs. What ideas/suggestions do people have?

Grassyass

D-Day

Spark plug fouling repeatedly - LTZ 400
 

You are either running to rich, or you are burning oil.
Check your air cleaner, clean if dirt. The carb could be sticking and making it run rich also.

Does it seem to be losing oil and has no leaks. Oil could be getting past the rings and into the combustion chamber, or leaking thru the valves.

Does it seem to be smoking? White-ish gray would be running to rich. A black/dark gray would be burning oil.

Rob

Spark plug fouling repeatedly - LTZ 400
 

Well what octane gas are you running in your quad and are the spark plugs gapped corectly...Rob if what you suggested doesn't make a difference wouldn't you think the cdi could be on its way out or some other short electrically.

Spark plug fouling repeatedly - LTZ 400
 

OK, I'll clean the air filter, and try to check/clean the carb...
Naw, it seems to be doing well on the oil... no leaks that I've noticed, and no smoke. I'll keep a close eye on the oil level to be sure that it is not dropping...

Thanks for the reply!

Spark plug fouling repeatedly - LTZ 400
 

Hey- well, it's gas from the tank that the owner of the land uses (several hundred-gallon tank). So, I don't know what he gets, but I assume that it's 87 or something standard like that (he uses it for his farm equipment, 4-wheelers, snow-mobiles, etc.).

Hmm, well, I dunno what the "cdi" is... I suppose it could be going out, but, what is it? Yup, it is quite possible that there is an electrical short on that thing, too. I'll give it a look-see for any obvious electrical issues (bare wiring and what-not).

Thanks for the suggestions!

D-Day

Spark plug fouling repeatedly - LTZ 400
 

You should clean the air filter every few rides. Get some hot soapy water and was it really well in it. Don't ring it out but use gentle squeezing to clean it. Rinse it well and shake out as much water as you can. Place it infront of a fan till dry. Oil it after it is dry with a good quality foam filter oil. I put alittle bit of oil in a ziplock bag then put the filter in and squeeze the oil into the filter. I would recomend going to the gas station and getting some fresh gas also. The gas in the tank may be alittle old. Try all that first before messing with the carb.

This would also be a good time to do a full maintanence check on the whole machine. Get good quality Motorcycle oil and a new filter, grease it and just check it out. I wouldn't worry about the CDI or anything like that until you check out what I said first. Always check the little things first.

Rob

Spark plug fouling repeatedly - LTZ 400
 

like what was said before it sounds like a jetting problem to me

Spark plug fouling repeatedly - LTZ 400
 

Mucky shoudln't the z's use a high octane gas such as like a 92...give the gas and electrical system a look at and see if they are performing correctly...the cdi pretty much lets the quad rev out and gives it a certain amount of spark

Spark plug fouling repeatedly - LTZ 400
 

the manual says you can use 87 but recomend using 91 or higher. as for the cdi it controls the spark timing and revs,but if the timing chain is stretched it could change the way it fires, if it has a bad spark it could be the igniton coil, the generator, the pickup coil or the cdi, does the quad use any oil? might be valve seals leaking, but to me it still sounds like s carb problem

Spark plug fouling repeatedly - LTZ 400
 

Make sure your choke is not sticking, and you do not leave the fuel valve in the prime position.