TOPIC:

Hi Guys, and possibly Gals? I have a 1980 kz 1300 A2 and I am having problems with the engine stuttering and missing when pulling away from a standstill up to about 2000 revs when it clears and runs normally. It only happens when the engine is warm , it is more noticable after a long period of overun for example slowing when coming up to traffic lights and then pulling away. I have changed my coils , thinking this was the problem ( they were split and the ht leads were shot) but the problem persists. The problem is not there when cold. Any help would be appreciated.
Jabee

Sure sounds like blocked idle transition ports. At the brass butterfly valve in the carbs are 3 tiny holes. At dead idle, probably one and part of the second are feeding fuel to the engine. As you open up the throttle more of the second and the third are starting to feed the engine with fuel as the vacuum increases in the main venturi and starts to open up the main circuit. What you are describing is a classical blockage of the transistion ports. Scotch has written up a method of cleaning these transition ports and if you follow his write up, you should suceed. Better yet, buy Scotch's transistion port cleaning tool. Scotch has put a lot of thought and consideration into this tool design and manufactures the tool specifically for this problematic issue with these carbs found on the KZ1300.

This problem will reoccur due to the ethanol that is now being blended into the fuels of today. Prior to ethanol blending you could store gas up to 5-6 months before it went stale. If you added fuel stabilizer you could extend that period to one year. Ethanol fuel will not stabilize with standard fuel stabilizer. The chemical compostion is not suitable. you now need to use fuel stabilizer specifically designed for ethanol blended fuel and it's not cheap. Standard stabilizer is about $8.00 a bottle. Same size bottle of fuel stabilizer for ethanol blended fuels is around $18.00 a bottle and treats around 300 liters of fuel. Ethanol blended fuel without stabilizer has a shelf life of 6-8 weeks maximum. 6 weeks in a vented fuel tank and possibly 8 weeks in a sealed jerry can

Kawaboy , thanks a lot , I will burn some midnight oil and check this out, the bike was an import from the good old USA and I recon its been standing around with old fuel in it for quite some time.
jabee

I have had self same problem on mine. As well as clearing those ports I found new pilot air screw O rings improved things no end (I also found 2 of the diaphragms slightly see through)

Haggler wrote: I have had self same problem on mine. As well as clearing those ports I found new pilot air screw O rings improved things no end (I also found 2 of the diaphragms slightly see through)

How or what do you mean by "slightly see through" Did they have cracks in them? I don't think I've ever seen diaphrams so thin you could almost see through them. Curious by what you mean here.
KB

there were parts where the rubber had come away leaving almost like a fine mesh. Will try and take a photo later. It was strange as I had missed it first time