This feels like another “Weak Spark” help thread but I’ll go ahead anyway because Ive ran out of knowledge.
In short I’m having trouble with my 1980 cb750f not running on all four cylinders. 2/3 seem to get to temp pretty quickly while 1/4 are cold.
So far I’ve tested :
-Primary and secondary resistance on coils - within spec for 3ohms coils.
-Swapped coils to cylinders
-12v to Black / white wire when ignition on. Yellow on RHS blue on LHS (while sitting on bike)
-Swapped cdi spark packs with each other and with another set of known working ones. Also tested 12v to 0 test in workshop manual. Mine test drop to 1v not 0 ?
- Tested resistance across yellow and blue wires on pickup harness 530 ohms on each
-Sprayed Aerostart product into 1 and 4 with now bang.
- all 4 Plugs have blue spark when grounded on rocker cover bolts
-D8ea plugs with new leads and Ngk 5ohm resistor caps
Bike is running brand new rs34 balanced mukinis
I can find timing Marks for 2/3 when timing light is connected to 2/3 leads. I cannot find 1/4 mark when connected to 1/4 - it’s not even close. I only screw/spring on auto advance unit .
With a little throttle assistance ( cracked open a little) I can get bike to run 2/3 but then dies as soon as let go.
Mukinis were purchased from Mukini OZ and are jetted for dohc cb750f
I’ve searched and searched for previous help that everyone here has previously posted so I apologise if this is another one of the same threads.
Any help or instruction? I’m happy to learn
In short I’m having trouble with my 1980 cb750f not running on all four cylinders. 2/3 seem to get to temp pretty quickly while 1/4 are cold.
So far I’ve tested :
-Primary and secondary resistance on coils - within spec for 3ohms coils.
-Swapped coils to cylinders
-12v to Black / white wire when ignition on. Yellow on RHS blue on LHS (while sitting on bike)
-Swapped cdi spark packs with each other and with another set of known working ones. Also tested 12v to 0 test in workshop manual. Mine test drop to 1v not 0 ?
- Tested resistance across yellow and blue wires on pickup harness 530 ohms on each
-Sprayed Aerostart product into 1 and 4 with now bang.
- all 4 Plugs have blue spark when grounded on rocker cover bolts
-D8ea plugs with new leads and Ngk 5ohm resistor caps
Bike is running brand new rs34 balanced mukinis
I can find timing Marks for 2/3 when timing light is connected to 2/3 leads. I cannot find 1/4 mark when connected to 1/4 - it’s not even close. I only screw/spring on auto advance unit .
With a little throttle assistance ( cracked open a little) I can get bike to run 2/3 but then dies as soon as let go.
Mukinis were purchased from Mukini OZ and are jetted for dohc cb750f
I’ve searched and searched for previous help that everyone here has previously posted so I apologise if this is another one of the same threads.
Any help or instruction? I’m happy to learn