QuestionI have run into some recent problems with my 1981 KZ 250 bike. I have about 10k original miles on the bike and have come across a problem where it seems like it is starving for gas. The symptoms are - a long warm up time with choke (about 5 minutes in Florida), some back fire, and loss of power. Sometimes I will be driving along at 50 mph and the bike with start with a few back fire and loss of power where I will have to pull over and wait for it to resume idle speed. It seems like it is choking for gas or is not getting the proper airflow. Other times I will be OK until I get to a stop light - when I pull the throttle it sounds like it is missing / starving and does not have much power (if any). I have changed the spark plug, checked the carb for water in the bottom, pulled out the cockpin and made sure there was not any other dirt. Do you think it is possible there is dirt in the carb? Also, do you know if there are points that can be cleaned? Any help would be much appreciated.
AnswerRyan, you may have noticed that Kawis are not my primary interest and experience, so I had to go to www.bikebandits.com to see some illustrations on your bike.
Apparently, the 1981-D2 KZ250 was the first year for electronic ignition, so all you can do is to make sure that all electrical connections are clean and tight and pray that there are no failing components in the circuit.
I am a little baffled on the "cockpin" reference. There is a petcock on the fuel tank which is the fuel valve, changing from On to OFF to Reserve. You might check the fuel bowl for debris or water. If there were restrictions in the fuel tubes going into the fuel tank, you will have to drain the tank, remove the petcock and disassemble and/or blow air through all the passages, to ensure that fuel is getting through properly. If there is no rust, water or other debris or corrosion in the fuel tank, then hopefully you are okay there. It only take a rogue drop or two of water in the fuel system to start plugging things up and causing misfiring. After 26 years, a carb clean is probably in order. These carburetors have a rubber diaphragm which lifts the slide and they can get some pinholes or tears. If there is any kind of defect hole in the diaphragm then it will never run properly.
The "new gas" with alcohol in it, makes engines run lean and with less power. Kawis were known for lean jetting back then, so this can only make things worse. Check the gas cap for proper venting, so you don't create a vacuum inside the tank and vapor lock the fuel system. Check your intake manifold for any cracks or other sources of intake air leaks.
Have the spark plug cap checked for possible excess resistance.. should be around 5k ohms. Check your air filter for cleanliness and that all the air filter housing connections are intact.
Be sure your charging system is fully functioning and the battery is fully charged, so the electronics are getting full voltage that is required.
If you pull the carb, drill off the idle mixture screw protective cap, so you can make a further adjustment to richen up the idle mixture. That will help the cold start and idling conditions. The parts lists show some optional main jets which may make sense to explore given the fuel and jetting issues facing us today.
Hope that gives you some ideas for solving your problem.
Bill Silver
