Author Topic: Odd spark problem  (Read 555 times)

Offline Northy

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Odd spark problem
« on: January 19, 2020, 03:57:45 PM »
I've  think I sorted it .......but its a weird one (Northy what hell are you talking about !!  ::) ::) )

Well for few weeks I've had this problem with the special 400/4 . After about 8/10 miles it would lose number 2/3  cylinders with no spark.The more you used the revs the less miles you did, so heat related? however wait 5 minutes and it runs Ok on all four, for about 4-6 miles.
This was PIA as it fixed it self before you got to testing things.   >:(

But Coil I hear you say ! ::) ::)

So replaced the new DS one with an old one ..same result
Replace both coils and leads/cap from my other 400f ...same result
Swapped plugs ...same result 
Replaced the condensers from my other  400f, clean points (again) ...same result
Checking wiring/connecting ...all seem ok
Not water related as only used in the dry
Thinking of making up a new wires from the points to coil or pleading for help on the SOHC forum  ;D ;D

Then today I had a thought (yes the 2 brain cells clicked in) this followed yet another run of 10 miles, then it goes onto 2. What haven't I changed and what have I changed. As the other 400/f with the swapped out part runs fine.

Well it took 1 minutes to fix it ......I managed 22 miles with not even a misfire , lots of revs etc (by which time it was getting colder )

The possible culprit .....

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I don't know why but replacing this with the standard chrome points cover sorted it. I had fitted it a few months back. 

Its not clearance issue but the ally one does get a lot warmer then the chrome one .This could point to something (points/condenser) breaking down under heat. The final test is refit the ally one and see if I can make 22 miles. (way too cold now for that )

So I think its sorted but its an odd one .....anyone had issues like this ? 



 
 
 
   




 

 
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Offline K2-K6

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Re: Odd spark problem
« Reply #1 on: January 19, 2020, 07:24:04 PM »
Doesn't the original have a coating on the inside of cover?

Got a photograph of of the inside of both covers to look at?

Offline SteveW

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Re: Odd spark problem
« Reply #2 on: January 19, 2020, 07:42:38 PM »
Mine has some kind of greyish coating on the inside of the cover.
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Offline Nurse Julie

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Re: Odd spark problem
« Reply #3 on: January 19, 2020, 07:45:26 PM »
Yes, mine does as well. It's defo some insulation of some type.
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Offline Northy

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Re: Odd spark problem
« Reply #4 on: January 20, 2020, 03:40:05 PM »
Yes there's  a grey coating on the inside of the original cover .Original I thought this was just is grey paint to save on chrome.
Appears Honda knew something !!!

So will add some insulation tape to inside of the ally and take it for spin ........and report back.   


 
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Offline Northy

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Re: Odd spark problem
« Reply #5 on: January 24, 2020, 12:49:49 PM »
Ok had ride in the freezing cold with the ally points cover on but with insulation tape on the inside, managed 16 miles running Ok.  Should have done some more miles but it was cold !!  ::) so it may not have got "hot" enough to be proper test.

So its appears for some reason when warm/hot the points sort out against the cover ?? this seems odd to me.

However one bit of logic is that points for 2/3  cylinder are closer to the cover than 1/4 and that's the one that fails.     

So I've  learn't something new .......or the garage fairies are having a laugh.  ;D
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Offline taysidedragon

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Re: Odd spark problem
« Reply #6 on: January 24, 2020, 07:01:12 PM »
Ok had ride in the freezing cold with the ally points cover on but with insulation tape on the inside, managed 16 miles running Ok.  Should have done some more miles but it was cold !!  ::) so it may not have got "hot" enough to be proper test.

So its appears for some reason when warm/hot the points sort out against the cover ?? this seems odd to me.

However one bit of logic is that points for 2/3  cylinder are closer to the cover than 1/4 and that's the one that fails.     

So I've  learn't something new .......or the garage fairies are having a laugh.  ;D

I'd guess that the new aluminium cover is thicker than the original chromed steel cover and that could put part of the inner surface closer to the points. Without any insulation there would be an increased chance of a short. Heat expansion of the metal might just put it close enough to make the difference?
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Offline K2-K6

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Re: Odd spark problem
« Reply #7 on: January 24, 2020, 08:20:07 PM »
Just a theory,  but it may be air ionisation within the covered area altering the relevant conductivity surrounding the points.

Start it in the dark and look to see if one set of points shows more sparks,  2/3?  And maybe the performance of that condenser is not as efficient as the others. 

If that were the case and conductivity changed during use, it may just swing it such that the one set is jumped and effectively results in the coil not switching.

Looks like Honda where onto it with their original coating of these covers anyway.  There's so many of these very small details on Honda bikes over the years,  almost exist invisibly until removed and you see why they were there.

Offline Oddjob

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Re: Odd spark problem
« Reply #8 on: January 24, 2020, 09:52:23 PM »
I thought the paint inside the cover was zinc paint to prevent the inside of the cover from rusting. I've used a LOT of zinc paint in the past and it looks identical to me.
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Offline AshimotoK0

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Re: Odd spark problem
« Reply #9 on: January 24, 2020, 10:42:00 PM »
I thought the paint inside the cover was zinc paint to prevent the inside of the cover from rusting. I've used a LOT of zinc paint in the past and it looks identical to me.

It's has a cement like filler in it . Not sure its for electrical insulation or sound deadening to stop 'ringing' I guess the latter because on the CB250/350K the tacho cam bearing cover has that coating and has no electrics inside of it.
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Offline paul G

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Re: Odd spark problem
« Reply #10 on: January 25, 2020, 07:57:39 AM »
I thought it was for ringing Ash. Has anyone had a meter across it.
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Offline Lobo

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Re: Odd spark problem
« Reply #11 on: January 25, 2020, 01:20:50 PM »
... I dunno Northy, but my gut feeling is you’ve a gremlin rather than a localised heat issue. My reasoning is that these bikes were sold worldwide, and operated in far higher temps than you typically see in the UK. (and you’re experiencing this issue in winter)
Furthermore, they’d have been raced / hammered / two up climbing hills etc -  surely a heat problem will have reared its head and be well known 40 years ago... even with the OEM cover.
We need Ash to arrange a thermocouple by the points for each of the two covers!

Offline Bryanj

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Re: Odd spark problem
« Reply #12 on: January 25, 2020, 04:12:16 PM »
I distinctly remember having to put insulating tape inside 250 K4 point covers to stop them shorting out a set of points, perhaps pattern points are a bit close to an aftermarket cover?

Offline Northy

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Re: Odd spark problem
« Reply #13 on: January 26, 2020, 12:12:48 PM »
Just done 40 odd miles and no issues .... so it "fixed" .

However as lobo says   "gut feeling is you’ve a gremlin rather than a localised heat issue. "   

Next step I suppose is to remove the insulation tape to finally prove it. That will have to wait ...need to clean the bike now, rather grotty roads out there today. 
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Offline Lobo

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Re: Odd spark problem
« Reply #14 on: January 26, 2020, 10:12:13 PM »
... a bit obvious, but this weekend I swapped a duff Newtronic ignition out for a new Boyer. What I noticed is where the blue / yellows exit the case, there is a sharp edge to the OEM cover which could conceivably chafe the wires. (My grommet is not OEM). Have you got an issue in this area, and in switching covers promoted the issue?
« Last Edit: January 26, 2020, 10:23:43 PM by Lobo »

 

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