Topic: 74 CB750K won't start

[tx750]

Hi, I'm new here and i have a problem with my CB750. It's getting fuel,Pulled plugs,Getting nice blue spark to all 4.Turns over fine just will not start.Will someone help before i start crying!

[boatsdickson]

Have you checked the contact surfaces on your points, and clearances too? Make sure your battery stays charged with all the crankin...

[tx750]

No, I haven't checked points yet will check shortly! thanks!

[tx750]

OK,I've pulled the carbs & cleaned them,checked points,good.Shot starting fluid into cylinders, still nothing!Ignition switch is on,will it still get fire to plugs if switch is bad?

[boatsdickson]

It sounds like youve already eliminated the switch theory based on your first post, (getting good blue spark on all 4). If the switch is on, and its allowing the starter motor to crank, and producing power to the plugs, I would check your fuel and air delivery on the carbs.

[tx750]

OK ,fuel & air delivery, have to do some research!Should'nt it attempt to start with the carbs pulled and spraying starting fluid directly into the intake rubbers?

[BobbyR]

Spray some carb cleaner into the carb throats and see of she at least farts. Then you will know it is a fuel problem.

[tx750]

Went to Honda got a set of plugs and put them in.Sprayed fluid and still nothing. pulled the plugs again to check for spark.2 & 3 were good,1 & 4 were dead.Graveyard dead!Went back to the points and checked gap again it was good.took an emery board to the contacts.Tried it again and it fired off!So i don't know if i got bad wires or what but it's gonna live! Any ideas on what might be wrong now?

[750goes]

check your points wires from the points plate back to the coils and particularly the connections in the wiring harness where they connect roughly in the same place as the rear brake switch...clean all the connections with some emery paper, and make sure they are nice and firm couplings (two dogs)..

give the points a wipe through with some alcohol based cleaner as well..

[BobbyR]

check your points wires from the points plate back to the coils and particularly the connections in the wiring harness where they connect roughly in the same place as the rear brake switch...clean all the connections with some emery paper, and make sure they are nice and firm couplings (two dogs)..

give the points a wipe through with some alcohol based cleaner as well..

Ditto on that point. I found the primary wires leading to the points plate frayed to vibration. I had an intermitant loss of # 1&4 and then they crapped out. I know for experience you can get about 45MPH out of two cylinders. When I installed my Dyna S I took special  pains with the routing and also added some tubing over the wires.

[tx750]

Thanks guys,
This thing had me worried. I bought it about 6 months ago for a $100 and all I had to do was clean the tank & carbs,fresh gas & a battery, and it started first kick after sitting in a back yard since 99.I'll give it a good tune up along with the instructions ya'll gave me & I think it will all be cool!


Hey, One more thing,Does anyone know what the red light in the nut that holds the triple tree is? I've heard it it that it might be a speed warning light. what little info i've found suggests that my 74 is a jap spec bike.Does anyone know how to tell for sure?
It also had a headlight with this huge bulb and a small orange running lamp in a sealed unit. i had to replace it because it was cracked.When tried to find another one like it i was told it was a U.K. only part. That's when i really got confused!any info would be appreciated greatly.Thank you!