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Discussion Starter · #1 ·
Honda cb400t December1977
Hi All,
After almost 6 years, complete bike rebuild as a cafe racer and rewired, had running fine but only for a couple of minutes.
Whilst trying to sort out wiring to the new speedo, noticed that the [new lithium] battery drains really quickly when the ignition key is turned to the on position, but does not blow the 15A fuse.
Don't know where to start checking, no smell of burning or over heating.
Any advise would be greatly appreciated.
 

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Rather than arc the battery cable lead to the battery and cause a spark, undo the ground cable off the other end, then tap without the key on. See if it is less than 12v now.

Key on, tap the ground cable to the frame. Blue arc is a short. Orange arc is normal.

Now pull one fuse at a time, arc the cable and see who does not arc so strong?
 

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Could you answer the following please....

1. I think it would be good to know how far you have strayed from the UK spec ( I assume it's a UK spec bike rather than an "import" ) wiring, if at all ?

2. Does the battery go flat quickly if the ign switch is always left off ?

3. You have an ammeter and know the load on the fully charged battery when ignition is on and engine in neutral, ignition killed, all lights off ?

How many amps drawn ?

4. A picture of the battery with specs, as it may be a small battery cos it's on a cafe racer.

5. I assume no led's used.

6. I assume the fuse box is mounted as standard and not suffered from overheating ?


Over.....
 

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Excellent point Mike, wonder how warm the reg/rec and yellow stator wires got, if they did.

As we know other than the diode effects, they are effectively permanently wired to the battery.

I wonder if the charging system was damaged before...as we know the reg/rec is reasonably robust on these as is the stator charging circuit, but not indistructable.

Personally I have not come across a "dead" charging system on these yet, plenty of others yes, but not this/these models, but there is always a first time.

Feed back feedback feedback, it's good manners......
 

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Discussion Starter · #6 ·
A couple of photos.
IMG_3488.JPG
Could you answer the following please....

1. I think it would be good to know how far you have strayed from the UK spec ( I assume it's a UK spec bike rather than an "import" ) wiring, if at all ?

2. Does the battery go flat quickly if the ign switch is always left off ?

3. You have an ammeter and know the load on the fully charged battery when ignition is on and engine in neutral, ignition killed, all lights off ?

How many amps drawn ?

4. A picture of the battery with specs, as it may be a small battery cos it's on a cafe racer.

5. I assume no led's used.

6. I assume the fuse box is mounted as standard and not suffered from overheating ?


Over.....
Hi, Thanks for responding.
1. Yes it is a UK spec. bike. It is no lights or indicators, rewired as ditched the old loom.
2. Battery holds a charge with the ignition switch off. but drops within seconds to zero with ignition on.
3. Not sure how to answer this question.
4. Will send a photo of the battery when I work out how to attach photos. It is a L P LLithium Life ML LFP9, 36Wh.
5. No leds.
6. Fuse box okay.
7. New rectifier fitted in open area under wiring tray.
Hope this helps.
Cheers, David
 

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Kick start engine ?

36wh.....and a life battery.....

Mmmm, will have to check spec of that, and nature of charging it....

Awaiting picture....I have used the attach symbol, the paper clip, or the camera symbol may work.

Would be good to know current drawn on switch on, which, with all lights etc off, should be nil. Ign system a self contained cdi system only needing battery for starter motor....

Still, try mike's suggestion of disconnecting reg/rec, which has a black wire battery voltage sensor.
I am sure you know black wire is battery + 12 volt after the main ign switch.

I assume battery fully charged.

Multimeters usually have a 10amp or more ammeter function. Maybe an analogue meter would be better or a dedicated ammeter...

You know how to use an ammeter ?

Lovely day here, stuff drying out, ready for a re soak with tonight's biblical rainfall...

Over...
 

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Also, since you have made your own loom, please post your wiring diagram, the diagram you followed to make the loom.

You did make a diagram to follow ?

Hopefully it's in colour, has a "legend", and switch diagrams showing switching connections ?
 

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Done a little research on the land port battery. Instruction sheet table 1. Is usefull.

How old is the battery ?
I presume it's new ?

Would I use one, depends on price versus cheapo lead acid standard battery.

My/our sd's are all bog standard apart from motad 2 into 1 exhausts. Purely used as basic transport and acquired when they were cheap, unlike now.

You would have though I would have had enough of them in the 80's. Super sport 250, super slug more apt. Super dream, more bloody nightmare as I have seen quoted.

The 400 is quite nice, the 250 less so but it is fun on the back roads.

Winter has arrived, snow on the mountains. Grrrrrrrr...brrrrrrrr......a bit cold.

Anyway, feedback....
 

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Discussion Starter · #10 ·
Hi, Having problems with downloading photos so they will have to follow. I have disconnected the 3 yellow wires that go to the alternator all 3 are down to earth. As soon as I took the outer cover off it had that tell tail smell. I now have to check if the problem has been caused by my faulty wiring or just failed through age. Thanks guys.
 

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Try this. I don't know what they call it, but say the pallet bar below the post window. Run your courser over the photo icon, that is left to the camera icon. Press that and it says two choices to make. You can drag and drop from your photo saves of that url. Unless you can find them in the hard drive, then you click the popup window or the second choice. This has the photos in one of your files to the left of that popup window. Find that JPG that you needed to use to send them to that website where your photos are.

We click your url for the image, we have to signup. These are your two moves for the loophole if I explained it well enough
 

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Hi David, the 3 yellow wires going to the battery charging 3 phase coils should not go to earth, infinite resistance to earth, star configured.

There will be continuity between yellow phases as star wound.

If any/all yellows go to earth then the stator is in need of a rewind.

Ouch, expensive.

As said never seen a "dead" one of these charging circuit wise .

Yours is the first one.

A yellow pinched wire perhaps ?
 

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Discussion Starter · #13 ·
Hi David, the 3 yellow wires going to the battery charging 3 phase coils should not go to earth, infinite resistance to earth, star configured.

There will be continuity between yellow phases as star wound.

If any/all yellows go to earth then the stator is in need of a rewind.

Ouch, expensive.

As said never seen a "dead" one of these charging circuit wise .

Yours is the first one.

A yellow pinched wire perhaps ?
Yes the 3 yellows are down to earth. Trying to remove alternator central nut, can you confirm if its right or a left hand threaded nut ?
 

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Hi David,
Cb400t 1977.

This has a kick starter ?

On the clutch cover, there is no slotted round plug at all ?

The 3 yellow wires are connecting to earth, BAD !!!!!

The flywheel has a central BOLT not a nut. If you see a nut summit is wrong.

Send a picture please.

You have a 17mm hex socket and longish breaker bar ?

You have a 19mm hex socket that fits the breaker bar ?

You have a good wooden mallet, mallets are usually for woodwork and chiesel, woodworking chiesel.

You have a one foot length of 3 x 2 wood, prefferance a hard wood but pine would do ?

Bike on centre stand, a chair of convenient hight, remove flywheel cover.

Now post pictures.

No left hand threads on this bike anywhere.

You have a good local nut and bolt supplier ?

Is the hex on the oil filter bolt good ?

Feedback please.
 

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Hi David,
Cb400t 1977.

This has a kick starter ?

On the clutch cover, there is no slotted round plug at all ?

The 3 yellow wires are connecting to earth, BAD !!!!!

The flywheel has a central BOLT not a nut. If you see a nut summit is wrong.

Send a picture please.

You have a 17mm hex socket and longish breaker bar ?

You have a 19mm hex socket that fits the breaker bar ?

You have a good wooden mallet, mallets are usually for woodwork and chiesel, woodworking chiesel.

You have a one foot length of 3 x 2 wood, prefferance a hard wood but pine would do ?

Bike on centre stand, a chair of convenient hight, remove flywheel cover.

Now post pictures.

No left hand threads on this bike anywhere.

You have a good local nut and bolt supplier ?

Is the hex on the oil filter bolt good ?

Feedback please.
 
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