SOHC.co.uk Forums > CB350/400

Many steps forwards, a couple of steps back. Hopefully sorted now.

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gtmdriver:
I've never had a 400. To be honest I was never keen on the styling.

Performance is limited as it's a heavy 350 and I'm a heavy bloke. It's more like riding a 250 really but the sound of the 4 pipes is brilliant. Especially on the overrun

gtmdriver:
It's taken a week but I think I'm back to making forward progress.

I replaced the lost side panel logo with a new aftermarket one from David Silver. Unfortunately it is a stick-on like the one which fell off. Strangely, when I had a close look, the badge had been moulded with the original mounting pins in place then these had been cut off to allow the double sided sticky tape to be used.

I also replaced both coils with new aftermarket ones from DS Spares. These bolt straight on in place of the old ones and have extra long plug leads which you can cut down as required.

I also decided, while I was sorting the ignition, to change to a contactless electronic system. I decided to go with the Boyer Bransden unit. Kit 00089 is listed for the CB400F and CB750F but correctly I assumed it would fit my 350F too.

I managed to mount the electronic box under the frame below the seat nose.



The rotor attaches to the mechanical advance unit AFTER the bobweights and springs are removed and the circuit board replaces the points back plate.



The Boyer Bransden unit has a built in electronic advance curve so the mechanical unit is not needed.

Like all aftermarket ignition systems the BB unit is designed to work with the stock coils. These have a primary coil resistance of 4 ohms. Fortunately I had the presence of mind to check the resistance of the replacements which was just as well as they only had a 2.2 ohm primary resistance which would have drawn far too much current through the BB electronic box. After checking with BB I used a couple of 1.6 ohm ballast resistors, one in the power feed to each coil.



The initial set up gets the bike started then you can use a strobe to accurately set the timing at the full advance marks.

Thankfully it fired up a treat on all four cylinders and drove very well.

An interesting feature of the BB ignition is that, with two pick up coils replacing the contact breakers, and a single rotating magnet replacing the cam each pair of plugs would fire once per crank revolution BUT the BB unit has two rotating magnets so all the plugs fire together twice per engine revolution.

I wonder what that does for plug life?

hairygit:
Probably no different for plug life than Honda's standard set up, which also had the wasted spark system, allegedly it helps keep emissions down.

Sent from my D2303 using Tapatalk

gtmdriver:
Yes but the BB system fires all the plugs all the time. Twice as often as the standard system.

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