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Hi everyone, i am new to this forum and need help getting my 1993 L model zxr400 import running right. Firstly the carbs won't balance properly, carb 1,2 & 3 will all sit nicely around 2 on the gauge but carb 4 is always closer to 3 and the needle is never steady, and you can hear this when reving the bike as it sounds like it may not be running properly on cylinder 4. The bike has new spark plugs, inlet manifold rubbers, carbs have been cleaned out, running standard jets, piper cross air filter element in air box, and an after market exhaust pipe. I was told to run 102.5 main jets to suit but am still not convinced this will see the bike running right, and was wondering what was other peoples opinions on the matter? will upload video soon so you can hear for yourself.
many thanks, Joe


http://www.youtube.com/watch?v=XqyfYZpW ... e=youtu.be

thats only running on 3 cylinders

id try the ignition side of things first

yep she's not firing on cylinder number 4!! but there is no corrosion on the coil contacts i am guessing the coil could be packing up?

it's likely to be not the coil, as it supply's no1 cylinder as well. Check/replace your ht lead on no 4, and also check that the vacuum rubber part of the carb slide on no4 is not split/punctured. Lastly swap no 4 spark plug with another. That should get you running.

detach the spark plug cap from #4 spark plug and then remove #4 sparkplug. then put #4 sparkplug back into the cap, touch part of the metal threaded part to the frame or engine, hold the spark plug cap (rubber, so its insulated) and without touching any bit of the metal parts of the bike (or you might get a shock) hit the starter button...if the plug is ok you will get a blue spark, if not you have either 1. dead plug, 2. dead HT lead, 3. a connection break between the coil and the plug, 4. a dead spark plug cap.

if you DO get a spark then you might have a fuelling issue with just #4 cylinder, check all your pilot air screw settings and check to see how much your carb adjustment screws have been previously set.

On the not balancing properly try resetting all the screws, sometimes people tighten them too much, to do this, remove the idle screw, look down the carbs and with the slides up, loosen the adjuster screws till they seat on the carb and try again

While one wouldn't like to contradict such expert advice.......................just swap the HT leads from 4 to 1 if the problem moves then it's likely to be ignition fault if the problem remains it's likely to be a carburation issue.

thanks for all your help and thoughts on the matter, i will be spending this weekend trying to get her running right now i know what direction to go in! will keep you all posted on how i get on