Not running on all cylinders.

[2 Wheel Virgin]

I recently purchased a Honda CB400T that needs work. It seems like the problem is only one of the two cylinders is firing. I checked the plugs (both are new) and the running side fires plenty hot and the bad side seems to make little to no spark. Replacing the rectifier was suggested to me, does that sound like a good place to start? Also what about a coil. It is a single coil with 2 plug wires so it seems like if it were the coil, it wouldn't fire at all. Thanks for the help.

[9000white]

switch plug wires and see if the dead cylinder starts firing --if it does you need new wires.

[mswarrior]

Do what 9000 white said. I rebuilt the very same bike a year ago, so if you still have problems i'll get into it.

[Quick 350]

It's funny a 78 CB400T just came in my yard not running last night. A friend picked it up for $200.00. It's been sitting behind the same bar for over 4yrs so it'll need some attention.

Played with it to day Changed the Oil, Plugs, Wires, Boots, And battery. Took the carbs off not that bad looks like some one drained the gas out of the tank and the bowls. Cleaned them up and slapped it back together. Added some fresh gas and with a few cranks of the starter she fired up.

She was running only on one cylinder as well. So I pulled the plugs "brand New NGK's" No spark on the left side. I swapped the plugs from one side to the other and no spark through it on the right side but the left had spark now.

Hmm! well I cleaned up one of the old plugs and tried that out and now had equal spark on both sides.

This has been the third NGK plug this year that was bad out of the Box.

Any one else had this problem with NGK's?

Mike Haverhill. Mass

[poppygene]

Any one else had this problem with NGK's?

Not yet, thankfully. Errrm, I wonder if they're Champions with an NGK label.

[Quick 350]

God I hope not!

I've never had bad plugs from NGK so it's really strange and they haven't been from the same store which make it sound like a bad batch for northern Mass $ Southern NH.

Lord knows I wont use Nepodenso I've had them burn up so many times it's not funny.

[cb360]

See my post from today (4/18 - same forum) Two Wheel Virgin. I was running on one cylinder and after a complete carb dib (which I needed anyway after 20 years of inactivity my carbs were nasty) I discovered that my immediate problem was a pinched wire under the points cover. A little electrical tape solved the problem. I hope your fix is as simple.

[Quick 350]

I thought the plug was the only problem but after taking the bike for a little spin it started to only run on one cylinder again.

Started to check through every thing and I discovered these bikes are twingles. Both cylinders fire at the same time. I didn't know

On to the electrical. A good amount of current was coming from the stator so I figured that was not it. Check the coil that was good as well.

Looking through the wiring harness I found (under the battery) a ground wire that wasn't connected to anything so I grounded it to a good spot on the frame. Runson both cylinders now.

Now I'm just waiting for a set of mufflers he ordered as well as a carb kit. Should be a good first bike not bad for $200.00 and $100.00 in a few parts and fluids.

[9000white]

i have read on some other forums about getting some bad ngk plugs.maybe ngk is outsourcing production to mexico.

[BuzZz]

NGK had a bad batch of plugs make it out of the factory not long ago. They should be offering refund/replacement for these, but arn't as far as I know. I'll be buying Bosch or Denso for 6 months or so......