I think the slides are in the wrong bodies

[Cappodimonte]

Hmmm! Tend to forget not everyone is a MotorVehicle Technician as easily back in the day. I did have my 400 run on 2 cylinders and noticed the performance drop off straightaway, cause was the yellow wire to the coil disconnecting.
Thank God Honda strap down Fuel Tanks with rubber which is  quickly detachable, my BSA Bantam stopped on me one night 3 miles from home in the dark, pushed it all the way home to find next morning the bullet connector to the contact points had come apart, having a British bike kept you fit.

[McCabe-Thiele (Ted)]

Hmmm! Tend to forget not everyone is a MotorVehicle Technician as easily back in the day. I did have my 400 run on 2 cylinders and noticed the performance drop off straightaway, cause was the yellow wire to the coil disconnecting.
Thank God Honda strap down Fuel Tanks with rubber which is  quickly detachable, my BSA Bantam stopped on me one night 3 miles from home in the dark, pushed it all the way home to find next morning the bullet connector to the contact points had come apart, having a British bike kept you fit.

In my defence I had never ridden the 400 before the rebuild - eventually the penny dropped with a combination of popping & banging - plus two cold exhuast pipes.

[Eldrick]

Are all the exhaust headers the same temperature, ie, equally bloody hot when you've been riding?

No is the answer to that, 1, 2 and 4 are too hot to handle and 3 is hot but not nearly as hot as the others.
So, can't rule out spark plugs just because they are new, so I will swap plugs from 3 and 4 around and see what I get. Failing that as the problem is it 'just' going to be the HT lead or plug caps?  I did re-set the gap on and clean the plugs when I took the carbs off. All plugs were a bit too dark but I expect that to change when I balance the carbs.

I guess it could be timing or valve clearance on #3 since I am quite sure the throttle slide does move freely as checked the play on them all when the carbs were off. All fore rise and fall when I engage the throttle manually and all the butterflies open and close too.

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update
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I just checked the plugs, #3 is still shiny and swapping it with #1 (which is black) made no difference. I then took the HT lead from #4 and connected that to #3, (no other leads are long enough to swap about) and #3 pipe got proper hot like it should.
I guess I need to do something with one or all of my HT leads then, but what?

[McCabe-Thiele (Ted)]

Once you have eliminated the Sparking you may have to look at fueling. If valve clearances are good then I would check the float level for the cooler cylinder.

[Eldrick]

Once you have eliminated the Sparking you may have to look at fueling. If valve clearances are good then I would check the float level for the cooler cylinder.

I don't think I have eliminated the spark, I think #3 is sparking sporadically. Putting #4 HT lead on #3 made it spark (the down pipe was hot)  properly. That does not meaan the coil is bad tho because #2 fires normally. I don't know enough about the wiring to #2 and #3 to safley say the coil is good or bad, I just think that the HT lead from the coil to #3 is at fault.

I suppose I could see if #3 lead will reach to #2 and see if it sparks there. if not, then I would be more certain that the lead or plug cap is at fault.

[TrickyMicky]

Re. swapping the plug leads about, No 1 and No 4 share the same coil and points. Likewise, Not. 2 and 3 share the same coil and points. If you put the HT lead from 4 onto 3 it will spark on the wrong stroke. This also applies if you swap 1 and 2 over.  Lift your petrol tank and check which leads are going to which plugs, plus to reassure yourself, make sure the low tension leads are connected correctly from the coils to the relevant points.  You mention that when you put No. 4 lead onto No. 3 plug the exhaust then got hot. Is there a chance that it was incorrectly fitted in the first place?  Have fun, it's a great hobby for keeping the old grey matter active. Mike.

[Eldrick]

You mention that when you put No. 4 lead onto No. 3 plug the exhaust then got hot. Is there a chance that it was incorrectly fitted in the first place?  Have fun, it's a great hobby for keeping the old grey matter active. Mike.

I don't think so, since the spark is is 'a redundant spark' I expected it to 'work' at the other end of the stroke to at least prove the fuel is getting through. So I think the leads aare all in the correct order. I just swapped them as a logical elimination step.

I will take the tank off again, tomorrow, and follow the leads to make sure they are   #1and#4 and   #2and#3.. If they aare not, then it needs new cables as they are not reaching anywhere else.
PS, I am having a good time doing this and learning.

[kevski]

You mention that when you put No. 4 lead onto No. 3 plug the exhaust then got hot. Is there a chance that it was incorrectly fitted in the first place?  Have fun, it's a great hobby for keeping the old grey matter active. Mike.

I don't think so, since the spark is is 'a redundant spark' I expected it to 'work' at the other end of the stroke to at least prove the fuel is getting through. So I think the leads aare all in the correct order. I just swapped them as a logical elimination step.

I will take the tank off again, tomorrow, and follow the leads to make sure they are   #1and#4 and   #2and#3.. If they aare not, then it needs new cables as they are not reaching anywhere else.
PS, I am having a good time doing this and learning.

  if  3 out of four are heating up your leads are on correctly, valve time and ignition timing will be correct, I would look at valve clearances on suspect cylinder then do a  leak down test, as well as swapping leads 2 and 3.

[McCabe-Thiele (Ted)]

If you are running on original coils I would certainly check where the lead comes out of the coil they seem to have issues there when the insulation rots separating from the central core. My 500 was very prone to misfire on one cylinder 1. When I fitted some inexpensive  aftermarket coils it started immediately not much cranking  needed as before.