Author Topic: 400/4 is popping & banging with poor mpg where to start?  (Read 818 times)

Offline K2-K6

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #30 on: June 18, 2022, 08:55:07 AM »
It'll be faster now Ted with all the plugs in the right order  ;D

And should be about 50~60 mpg.

Offline McCabe-Thiele (Ted)

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #31 on: June 18, 2022, 09:06:55 AM »
I will definitely need a couple of longer leads probably go for some proper caps too.

Anyone have a link to the right type of cap presumably screw on ends from a trusted source?

Is the angle of all four caps the same please?

Still can't get my head round the fact that the bike would even run on two cylinders - my feelings of stupidity will ease with the passing if time as long as I am not reffered to as "Two Cylinder Ted" for too long. lol

« Last Edit: June 18, 2022, 09:35:24 AM by McCabe-Thiele (Ted) »
Honda CB400 four super sport

Offline Matt_Harrington

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #32 on: June 18, 2022, 09:30:41 AM »
NGK, I suppose, would be the correct ones - DSS seem to be as good a value as anyone else. I think they were out of out of stock of the 2 & 3 red ones last week but that may have changed.
Matt
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Triumph 3T - 1946 - Now finished(ish)
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Offline Spitfire

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #33 on: June 18, 2022, 09:38:51 AM »
An easy mistake to make it would be logical for the leads on one side to go to the cylinders on the same side, but we live and learn, and that's what life is all about.

Cheers

Dennis
1976 CB750F

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Offline McCabe-Thiele (Ted)

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #34 on: June 18, 2022, 09:39:31 AM »
Ted,

1 and 4 on one coil.  2 and 3 on the other. (CB750). Almost certainly all the fours will be like this.

Jerry

Well spotted Jerry, yes you're correct and I think for all the Japanese fours ever made which all do this.

Ted, you'll not be the first as many others have done this over the years too including my local bike shop years ago. They asked me to look with them at a problem bike that they could not sort, they'd done exactly this,  :-[ all round.

Nice to know I am in good company K2-K6.

Honda CB400 four super sport

Offline Oddjob

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #35 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
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Offline K2-K6

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #36 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.

Offline McCabe-Thiele (Ted)

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #37 on: June 18, 2022, 10:56:14 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
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.🫣
« Last Edit: June 18, 2022, 11:19:08 AM by McCabe-Thiele (Ted) »
Honda CB400 four super sport

Offline McCabe-Thiele (Ted)

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #38 on: June 18, 2022, 11:00:58 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.
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.
« Last Edit: June 18, 2022, 11:21:23 AM by McCabe-Thiele (Ted) »
Honda CB400 four super sport

Offline McCabe-Thiele (Ted)

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #39 on: June 22, 2022, 07:44:51 PM »
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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Offline K2-K6

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #40 on: June 22, 2022, 09:07:08 PM »
Woooohooo Ted, now it'll feel good to ride  :)

At least not too hard to correct and get you back on track.

Offline McCabe-Thiele (Ted)

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #41 on: June 22, 2022, 09:51:58 PM »
NGK, I suppose, would be the correct ones - DSS seem to be as good a value as anyone else. I think they were out of out of stock of the 2 & 3 red ones last week but that may have changed.
Matt
Never mind the Red I've gone for stealth. Black!
Honda CB400 four super sport

Offline cbxman

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #42 on: June 23, 2022, 08:16:05 AM »
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.

Ted,  Be as generous as you can with lead lengths, as you may need to re-attach the caps one day, and the leads do deteriorate/ get mangled when you manhandle leads to get the plugs out!  Having some slack will help.

Have fun,

Jerry
CB750 K1 1971 Wisconsin, USA
Suzuki GT550 J 1972 Michigan USA
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Offline McCabe-Thiele (Ted)

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Re: 400/4 is popping & banging with poor mpg where to start?
« Reply #43 on: June 23, 2022, 10:40:41 AM »


Ted,  Be as generous as you can with lead lengths, as you may need to re-attach the caps one day, and the leads do deteriorate/ get mangled when you manhandle leads to get the plugs out!  Having some slack will help.

Have fun,

Jerry
[/quote]

Thanks Jerry you make a valid point - i'm leaving them slightly overlong for now. Ted

PS No more popping & banging - its gone!
« Last Edit: June 23, 2022, 10:44:51 AM by McCabe-Thiele (Ted) »
Honda CB400 four super sport

 

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