Topic: CB400f wiring harness with a CB350f

[camshaft1991]

I've been having electrical problems with my bike and I think I have deduced down to two possible problems, my coils and wiring harness. I have had issues with cylinder #4 misfiring even with new points. I also had a fire while tweeking my bike in fall, but the wires for the most part seemed ok after i re-wrapped them with electrical tape. I was wandering if wiring harness  32100-377-030 from a cb400f is compatible with a cb350f? The cb350f wiring harness is 32100-333-000. Is there really a difference in the two? The cb350f harness i have found are more expensive than the cb400f

[calj737]

The misfiring is more likely due to one of the following: bad condenser, spark plug cap/wire. If you swap 1/4 spark plug leads, does the issue travel? If not, look at your ignition. If so, check the resistance in the caps and inspect the wire very carefully.

An electrical fire?!?! The only reasonable explanation there is improper grounding/polarity. Unless the harness is vastly different and uses completely different routing, I would dismiss that. Inspect the actual grounds and insulation for evidence of where the fault occurred for best results.

[camshaft1991]

I have sawpped the caps and the wires, or one of the wires is too short to swap. And the fire was a combination electrical gas fire . The floats were offset so the carbs spilled out and the battery terminals were not secure. Gas fire but electric started it. but luckily i had nothing like my gas tank or side panels on. i read something about sniping the end of the coils.. it might help. I just bought a brand new pair of points and condensers that helped the bike idle but it still ran on three cylinders. It ran smooth for a week with the wrong ignition timing, but it could only be noticed with an inductive timing light. Then after that week it did not want to ride smooth at all. My bike is currently disassembled so i can replace worn gaskets and a broken cam chain tensioner bolt as well. Also before i started with my disassembly, my points for 1-4 gave off a big blue spark while 2-3 had a minimal spark and this was the same with my old pitted points and old condensers that i replaced.

[calj737]

The description you provide now sounds more carb/fuel level related than igntion. While you have the motor down, it would be a very good idea to fully and obsessively clean and adjust the carbs.

[camshaft1991]

The carbrs pass the vacuum test, but not with flying colors. I've taken them apart and reassembled them almost half a dozen times. I can take them off, take apart, clean, put them back together and back on in a hour. My point is i know these carbs and my 4th carburetor looks like one of the nicer ones compared to some of the others that run fine. When I adjust my air screw for carburetor 4.. as I limit air flow or tighten the screw, which increases the vacuum.. the idle increases. The other three carbs' air screws lower the idle when you screw in the air screw and limit air flow. Could my carburetor boot on the engine be bad? I can't see visible cracking/dry rotting but the carburetors are hard to get on the boots even with the hose clamps off. My floats lock up most of the time after draining carbs and turning the petcock back on, but the back end of screwdriver is enough to fix that or the heel of my shoe. My carbs are completely rebuilt with all new gaskets jets and needles and none of them show any ware beyond functionality, especially carburetor 4.  I heard something about spraying carb cleaner or igniter around carbs while the engine is running to see if any gets sucked in and increases the idle..   

[calj737]

Vacuum synch: adjusting the vacuum pressure will effect the idle while doing this. Try to get all 4 carbs equalled in pressure, regardless of the volume.

Carb clean: if you have persistent sticking floats, you need to address that. Either you have a fouled float or valve, or debris is regularly infiltrating your carbs.

[camshaft1991]

I'll get some carb cleaner for the floats. I even bought new float pins that helped a little. When they get stuck it's  like the valve jet switch inside is about to fall out. If I take my bowls off, hold my carbs ride side up then flip them upside down.. Most of the time they all lock up. It's like the switches are partially out and tapping floats/carbs settles them back in. But I'll clean and check my valve jets more extensively


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[camshaft1991]

To follow up on this, and to bring closure, there is a considerable difference between the two. First off the 350f wire harness utilize one fuse while the 400f utilizes 5 fuses. Thus both airboxes are configured differently. The 350F air box holds one fuse and the 400f air box holds 5 fuses. Everything else electrical related is identical: coils. regulators/rectifiers, points, pushstart, alternator, etc.