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Re-Awakening the CB750c - Part 1

Getting ready for Dyna coils, procom igniters, relay and wire work
It's been roughly 5 or 6 years since I took the suzuki carbs out of my CB750c. Ever since I put the OEM carbs back on, the bike has never run right. There was a high rpm stutter, then the accelerator pump was not squirting then the carbs got clogged from sitting for a few years while we settled into our new house and new life.

Last year I cleaned out the carbs to prepare it for the road and when I filled it with gas, I discovered a leak that sidelined the bike for another season because I couldn't bring myself to take the carbs off after wrestling them on.

This year I decided to give it another shot and removed the carbs to have a look.  Hoping I didn't have to completely tear down the carb bank to replace an O-Ring, I found a loose float bowl which was likely the cause of the leak last year and decided to give the carbs another quick cleaning just in case, even though I never got the bike started last year.

I decided to get a new accelerator pump kit because the last one I got came with a long pump shaft that I ended up trimming to fit but it was a slightly different length than the OEM part.

Order part, wait for delivery.

Carbs went on easier this year. I used a little soapy water to help ease them in and pushed the airbox boots into the airbox for extra room. Filled the bowls and no leaks. Success!

I thumbed the starter button and got nothing.

Tried pumping the throttle to get some gas primed and got nothing.

Tried holding the starter button while pumping the throttle and got nothing but the smell of a flooded engine.

WTF? Time to step back and start with the basics.

Fuel and Spark.

Since I could smell the gas I knew that part of the equation was OK.

Checked for spark and got nothing.

Found the fuse to the ignition coil relay blown. Replaced the fuse and it instantly started but sounded like a twin. Cylinders 2 and 3 were not firing.  Checked the plugs and they all had a weak spark.

Put in new plugs and she started right up on 4 cylinders. Gave it some throttle and it's back to running on Cylinder 1 and 4 WTF?

The non-contact infrared thermometer works great for checking the header temperature!

Swapped coils and cylinders 2 and 3 are still cold. WTF?

Swapped the procom igniters and now cylinders 1 and 4 are cold.  How new igniters could fail after sitting for 4 years is beyond me. Luckily, I found a new set of igniters on Amazon for under $60 with free shipping which is much cheaper than anywhere else selling for $79 plus shipping.

Drawing from my experience working on a free car I now understand that ignition coils can and do fail and since my coils are upgraded OEM honda cbr coils from a used bike, I felt like it's pretty much time to bite the bullet and put new ignition coils on this and the only game in town for this bike is the Dyna DC1-1 Green coils.

More parts to order and more time to wait for delivery. It's a good thing I have a job because it is getting expensive to bring this thing to life again.

With nothing more to do while I wait, I decided to try and finalize the fuel line routing that I've never been happy with. I think I went through 10 feet of fuel line redoing it in different configurations every few months.  I discovered that the yellow tubing I was using was not fuel safe. The gas that leaked out the yellow tube was yellow but the gas that came out of the petcock was clear. CRAP!.

Good thing I had some tygon fuel line from my purchases earlier in the month. I have no idea if the yellow gas in the carbs will clog or leave any harmful residue. I'll find out eventually.

I keep spending money on this bike and haven't really ridden it, not sure where I'm going with it, but we'll see after the new procom igniters and dyna green ignition coils make their way onto the bike. I'll most likely need a new battery while I'm at it since it won't charge past 80%. I wonder if the battery condition might be the root cause to some of my ignition woes.

After sitting for this long, I'm going to need new tires but I'm not buying those until after I get her on the road again. perhaps for next winter's project.

Reawakening the old girl (now 37 years old) has so far been a bumpy pot hole filled road. I hope I don't lose interest again when the weather gets crazy hot.

Coming up for Part 2

  • Dyna coils
  • Ignition wires
  • New relay wires
  • Irridium plugs
  • OEM 4 into 4 exhaust


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