Cylinder temp question

Posted by Jack G on Aug 19, 2010; 10:15pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Cylinder-temp-question-tp1233996.html


1975 Honda CB750K, #4 Cylinder about 160 degrees F cooler than other 4.
Compression all about 135 psig, overhauled the carbs fuel in bowl is clear and levels are
#1 & #3 is 45ml (1.5 oz), #2& 4 is 40 ml (1.4 oz)
Used a Fluke non contact thermometer and got the following temperature on fin at 12:00 position above exhaust pipe, outside temperature  was 25 degrees C ( 77 degrees F), bike brought up to temperature and at idle not moving
#1& 2 read 134 degrees C (273 degrees F)
#3 read 132 degrees C (270 degrees F)
#4 read 44 degrees C (111 degrees F)
Checked spark and was strong, has an electronic ignition system
My best guess is the #4 carb slow jet (it did look ok when carbs overhauled)