Newbie with motor issue 80' 250 LTD

So I am learning to ride on a 1980 KZ250 LTD. The bike has just over 7K on it and seems pretty solid. Bike starts good, idles good, and when it runs, well that is the problem. The bike hesitates, sputters, backfires, and feels underpowered when I am riding it out. The motor is getting mega hot. Smoke comes out of the cam where the points are. I put in a new spark plug and battery, and the new spark plug is white and not "tan" at all. It is clearly not running properly. The gaps on the plug and points is correct.

My neighbor seems to think that it is running "too lean". Please HELP!

Should I have the jet opened up? Should I also change the points and put in a new plug?


Thanks Guys!

whats the center electrode look like? possable causes preignition,overadvanced timing,incorrect advance,fuel octane rating not right,incorrect plug heat range that gives you a start, oh if I havent said it welcome to KZR,pics please

Welcome aboard. Before "opening up" anything I would give it a thorough tune-up, make sure the timing advancer is lubed and moving freely, clean the carb, etc. Also, have you changed the oil/filter and made sure it isn't overfilled? Is the exhaust and airbox stock? Ed

Has the bike sat for an extended period of time? You say it idles fine but runs kinda sluggish. Maybe your carb needs a good cleaning.

Your 250 was set up from the factoery to run on the lean side, so if there is any build up in the jets engine will be very lean. I would clean and inspect the primary and secondary main jets and the pilot system (which may or may not have a rubber plug installed in it). I would also reccomend the factory manual becasue it has very detailed drawings of the carburator passages and a great section on "Theroy of Operation" that makes cleaning an inspection a breeze. I owned one of those bikes for over 10 years and the carb has to be kept very clean or they get temperemntal. I opened up the both the primary and secondary jets to get just a little more fuel and my bike ran much better, but its VERY touchy and easy to run super rich. Also verify the diaphram on top of the carburator is not torn, that will casue all sorts of problems. The rubber intake manafold and air box need to be in good condition as well because air leaks have a big effect on such a small displacement engine.

Thanks, I'm going to get the carb ran through as soon as possible!