SOHC.co.uk Forums > CB350/400
400/4 is popping & banging with poor mpg where to start?
Oddjob:
It's not vital Ted but it's common to fit the coil for 1 & 4 on the left hand side of the bike and 2 & 3 on the right. You've clearly got them the other way round. TBH it's so common to do it that way that if you'd have said 2 and 4 weren't firing I would have suspected the leads on the wrong cylinders right off as I've seen that a few times, 1 and 3 not firing just didn't set off the warning bells for some reason and it really should have.
It's no wonder you thought the engine was underpowered ;D ;D ;D be careful when you get it right or you may be pulling wheelies ;D ;D ;D
K2-K6:
Thought the leads for these are resistance in the carbon lead and their favoured setup to go with the complete system. It may be wise to get new std spec (for dyna) leads to install to their technical specification.
It can impact the load on switching transistor (and looks to me one scource of unreliability in some of these electronic system) as debate about them often doesn't include that nuance.
McCabe-Thiele (Ted):
--- Quote from: Oddjob on June 18, 2022, 10:22:54 AM ---It's not vital Ted but it's common to fit the coil for 1 & 4 on the left hand side of the bike and 2 & 3 on the right. You've clearly got them the other way round. TBH it's so common to do it that way that if you'd have said 2 and 4 weren't firing I would have suspected the leads on the wrong cylinders right off as I've seen that a few times, 1 and 3 not firing just didn't set off the warning bells for some reason and it really should have.
It's no wonder you thought the engine was underpowered ;D ;D ;D be careful when you get it right or you may be pulling wheelies ;D ;D ;D
--- End quote ---
I connected my coil wiring as it was when I bought the bike taking a photo plus a note of the wiring colours & ignition wire runs so I duplicated the previous back to front arrangement.
That's the best defence I have your Honour.🫣
McCabe-Thiele (Ted):
--- Quote from: K2-K6 on June 18, 2022, 10:29:21 AM ---Thought the leads for these are resistance in the carbon lead and their favoured setup to go with the complete system. It may be wise to get new std spec (for dyna) leads to install to their technical specification.
It can impact the load on switching transistor (and looks to me one scource of unreliability in some of these electronic system) as debate about them often doesn't include that nuance.
--- End quote ---
My plan is to get some lead from the original source of my kit if possible.
Failing that The Green Spark Plug Co they seem to have a lot of options.
McCabe-Thiele (Ted):
Yes finally 4 hot down pipes - running on all four cylinders, Yes all 4 cylinders - I have a massive grin on my Mush even though I can't ride the bike today due to C2H5(OH) intake.
I will need to trim down the HT leads as I have left them slightly on the long side for the first fit!
Can't wait to try the bike on a run to Ashbourne probably tomorrow.
YES, YES, YES, YES. that's four yes's for four cylinders!
To be on the safe side I plan an oil change asap in case of sump dilution as a result of 115 miles on 2 cylinders.
Moped power to 400/4 now the HT leads fitted in the right order.
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