my 3tj keeps fouling up 1 of the 4 spark plugs and running on three cylinders . does it sound like a major problem?. it sits around a bit if that is of concern. it seems to be cylinder 2 that fouls up .what can i do?

When you say it's fouled is it oily ... ???? If so it could be the piston rings which is a big job.

If it's just black and sooty then it looks like the mixture is to rich - take the carbs off and clean them all, do it one by one so you don't mix the parts up. The two inside cylinders have different size main jets to the outside ones.
If the plug has a hard white deposit then it's running lean - agian clean the carbs but look for something in the jets. Don't stick anything metal through them, use carb cleaner to blow them through.
After either of these you should balance the carbs - you might want to get a garage to do it because it's fiddly and you need a carb balancer.

It might also be an electrical thing, this is less likely because each coil feeds two cylinders but have a look at the HT lead and plug cap just to make sure.

The last thing might be the valve clearances, again not so likely and it takes a bit of savvy to do them.

the plugs are always looking oily. is that not so good?
I have had a replacement top end fitted which was 1mm oversized rings and barrels . it doesn't blow any smoke.
So you think it could even be electrical? I have had the bike for 7 years and has always had oily plugs and fouled them up the carbs have been recently balanced and is running smooth. i will check the jets and make sure the right jets are on the right cylinder.

If the plugs are oily then it isn't good. There are only 3 ways it can happen: Going past the rings, but you had it rebored; Tracking across the head gasket - see if there's a brown foam in the top of the radiator or the oil looks grey; The oil seal on one of the valves has worn, look for a puff of dark smoke on start up.

It doesn't smoke on start up but it does spit out through the exhaust small droplets of oil while on the choke as soon as i take it off the choke it is fine. The head gasket is new but i will check the radiator and oil like you said and get back to ya.

I have checked the radiator and there is no brown foam, the oil looks normal and the bike doesn't smoke. I checked the rest of the spark plugs and they are all oily too. You say it might be the rings but wouldn't it puff out blue smoke now and then?

Yes.

It's a bit of a knotty one with no smoke blowing but I reckon you should have a compression test on it. You need a "dry" and "wet" test. A low dry reading will indicate a leak past either the valves or rings. Then they put a bit of oil in the barrels which seals the rings, so if you still get a low reading it's probably the valves and if the reading is higher it's the rings.

hey thanks so much for your help.

No problem I hope you get it sorted