@#%#$#% Plugs

[tecatecrazy]

I need some help from some of you super tuners. I am fouling plugs pretty regularlyand I need to know where to start (i think its carboration) My plugs are always wet and black, engine smokes like crazy and there is a nice greasy black coating on the inside of my exhaust. I just installed new rings and I have kiehin PJ carb with a 155 main jet (not sure what size carb is) and I now mix my gas at 30:1 per the service manual. The original Mikuni carb (32mm) had a 240 main jet in it, should I have the same size jet in my current carb or are they unrelated. I have never had a plug foul out at any time other than idleing. In the two months that I have had the bike I have gon thru approx. 10 plugs. The bike is an '84 tecate, come on guys work your magic.-----Joe

[tecatecrazy]

:?:

[tecatecrazy]

c'mon guys, this should be easy for you pros to figure out, please help---Joe :-D

[Lots_Of_Nothing]

umm...i dont realy know, sounds like the carb is adjusted wrong, or else your coil isnt making enough spark for it, the ignition coil could be worn out, or the air filter could be choking it out, but if it has just all of a sudden started this then i doubt its the air filter, but check just to be safe, are you getting the right kind of spark plug?

thats all i can come up with

[tecatecrazy]

The ignition is new (PVL) and I clean the air filter regularly. Ill check the spark tomorrow but I think its the carb, just not sure what. Could timing cause these problems, just a thought sinc the ignition has been replaced. I dont know what to do , but I tired of changing fouled plugs

[Lots_Of_Nothing]

well...sorry but i have no idea with that stuff, it should say in a manual what the carb should be set at

[TimSr]

It sounds like you have ruled out mechanical problems, maintenence, or problems caused by mechanical wear, so I would be inclined to lean towards carburetion too. First thing I wonder is what type premix oil, and at what ratio it was set up for. The manual may say 30:1 for their specific OEM oil, but the actual ratio is determined the type oil used. Most people now run synthetic premix oils at from 32:1 to 50:1. The key is select your oil, decide at what ratio, and stick with it, otherise youll be messing with carb settings everytime you refuel. My personal choice is BelRay MC1 at 50:1. Once you figure out what your going to run in the tank, and start running it, then you may have to address rich carburetion which can mean dropping jet sizes.
One other statement you made that caught my attention was that it only happened while idling. With cold weather here, a common problem is that a cold engine runs very rich until it reaches operating temp after which cold air in a hot engine makes it run leaner. If you decide to start it, then let it reach operating temp, before shutting it down. Even 4 strokes commonly have problems in winter from guys who will start them just to move them in and out of the garage and then shut them back off. Also let it reach operating temp before you start reving it up. Reving a cold motor feeds fuel faster than its burned. When I first got my TriZ I went through plugs a lot because I had the idea you needed to rev the heck out of it to warm it up right after starting, when I was actually flooding it. I lter learned to start it, and rev it only slightly above idle until it was warmed up. Hope this helps.

[Jeb]

First off, I think that 155 main jet is too small!! :shock: You had a 240 in the stock 32mm mikuni, I don't have the manual in front of me now, but 240-260 range is stock. I'm not sure what size Keihen you have, but I'd change the main, pilot, and needle back to stock Tecate and go from there.

Rich factory recommended mixing is even worse on the 84 Tecate. The service manuals, owners manual, and even sticker's on the trike say to mix at 20:1, which as TimSr has pointed out is way too rich for good racing oils. That rich is a waste of oil and bad on plugs, but good for spraying mosquitos and producing that black tar :-D . Lean the mixture out some. I personally wouldn't go any leaner than 50:1. As TimSr said, BelRay (which I use MC1 also) recommends one bottle to 5 gallons, which is 50:1. My 84 Tecate ran great at 32:1 with a 38mm Mikuni Flat Slide carb. I can't remember the jet settings, I'd have to tear into the carb to see.

There's a pretty simple test you can do. I hope I tell you right, if I'm wrong about this, someone please post. Or if there's an easier or better way please post also.

Put your helmet on :-D , get in a wide open area, and wind the Tecate all the way out in 5th gear. then kill the motor, don't shift out of 5th gear and let the compression bring you back down to a stop, the whole time holding the throttle wide open. Then pull the plug and look at it. You want a chocalate brown color on the end. If it's black, your too rich. If its a whitish yellow, your too lean.

Let me know what you find out! If anyone can add, please do.

[tecatecrazy]

As far as the mixture is concerned I used to run about 70:1 with suzuki oil because I thought that the initial problem was too much oil in the mix, but this really didnt help things. I have also turned the air screw or what ever it is on the side of the carb out an extra half turn to allow for the cold temps. With the fouling occuring at idle, could it be that the idler jet is too big? Tomorrow Im going to put in a 170 main jet to see what that does for me. Oh yeah Jeb, I haven't found a place to run it wide open in 5th gear yet, our atv park in town doesn't have any straight aways long enough and smooth enough to do so, its 4th gear full throttle and then lock up the breaks or you'll be picking bark out of your teeth. Thanks for all of the suggestions though fellers----Joe

[OldSchoolin86]

Hey Joe, it doesn't matter what gear your in. Here's what you do, warm it up by doing a little riding and then run her up in like 2nd or 3rd and hold it there for a few seconds. Just get the RPMs up but not in the total red just so your on the top end. After that kill it, get it out of gear so the motor isn't turning and stop the machine. Now you can pull your plug and check what it look like. Don't hold the throttle because you'll ruin your sample on the plug and don't use engine drag to slow it down it can do the same thing. You want the truest sample you can get. The idea is to see what it looks like when it's running at those RPMs.

good luck

[tecatecrazy]

Thanks OS now I got a good reason to take back to the park tomorrow, at least a good reason to tell the wife. hehehe

[tecatecrazy]

I also forgot to add one small detail , my exhaust has a pretty good size dent on the bottom just before the expansion chamber

[Jeb]

Thanks Oldschooling for posting that follow up on the plug test!

Joe, an exhaust dent will change the volume and effect tunning somewhat, but is it noticeable for everday riding, probably not. My 84 Tecate has a dent in the bottom of the pipe (same place sounds like yours is) and if it effected the tuning, I never noticed. :-D

Also, your running plenty lean on your mixture :shock: . Work with the tuning on your carb.

[tecatecrazy]

at the advice of dirtcrasher I am finally posting what I found to be wrong with the carb on my tecate ( dont quite have all the bugs worked out yet due to lack of riding) . I found that the main cause of fouling plugs in my case was due to the float being set to high which is adjusted by bending the tang on the float mechanism. Plugs are now a nice caramel color. I still however have a slight bog problem when running mid throttle ,but works out of it easily by slightly thumbing the throttle. Any imput on this problem would be greatly appreciated. Thanks---Joe 8)

[theeechozen1]

Switch to a good synth oil (bel-ray, power plus, golden spec) and run at 50:1 for a good ride to clean out your cylinder- that should clean up the bog down low and crisp up your performance quite a bit, but keep an eye on your plug!!! :shock: