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1987 V35ii coils

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Po51uhd View Drop Down
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    Posted: 06 Sep 2018 at 14:34
Hello
I’m struggling getting this to run properly. I’ve tried the carbs and they seem to be doing their jobs ok (checked with Colourtune). 
Points are fine and I’ve replaced the capacitors as a precaution. Static timing is right (can’t check advance as my strobe is knackered!)

I suspect the coils. This bike has conventional contact breaker ignition.
The coils are white, stamped ‘Nippondenso’ and the 2 primary and the secondary connectors are potted quite crudely. Black leads (labelled 12v) goes to CB and orange leads (labelled 9B) to ignition power. This seems wrong way round, does it matter?
I’ve checked resistances. Both primaries read 4.2ohms (seems high...?)
One side secondary is 8.75kohm, the other is 11.5kohm
Add in plug caps, secondaries are 13.75 and 16.9 respectively.

The bike runs like a pig and won’t pull under 3000 revs then pulls like a train above that. Tickover is unsteady.

Any thoughts or suggestions very welcome!

Thanks
Stephen 
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jefrs View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jefrs Quote  Post ReplyReply Direct Link To This Post Posted: 06 Sep 2018 at 15:34
Thoughts - flying kites

The Gunson Colortune won't indicate properly with modern unleaded fuel, however it does give a useful indication, "for indication only". I'd like to know who 'borrowed' my Colortune.

It is unlikely to be the coils unless they are tracking to ground or they have poor insulation, resistance to ground.

HT leads and plug caps do go down, but not as often as the spark plugs do. What looks like a perfectly good plug may not be.

Have you cleaned the points? A condenser may have gone down but unlikely for both to go at once though.

If you have good sparks then fluffing idle and low part of revs can be carbs need cleaning and idle resetting, further up the revs they're mostly on main jet not the idle settings; hence it goes well over 3000 maybe.  Could be dirty fuel, old fuel, blocked fuel filter.
Personally I initially tend to use an injector cleaner in the fuel (Redex) rather than stripping down as jetting stuff through holes can push dirt further in. If that fails, then the spanners. I do not know these particular carbs but I think I'd be looking for bypass and idle jets; whatever does the the 0-25% operation.  

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GC888 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GC888 Quote  Post ReplyReply Direct Link To This Post Posted: 06 Sep 2018 at 16:59
What jefrs said with a bit more emphasis on earthing everything.
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iansoady View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 06 Sep 2018 at 17:25
I seem to have (early days yet) cured the misfire on my V50 by fitting new plugs & caps. Cheap enough from the Green Spark Plug Company:

Ian
1982 V50
1952 Norton ES2
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jefrs Quote  Post ReplyReply Direct Link To This Post Posted: 06 Sep 2018 at 18:32
Originally posted by GC888 GC888 wrote:

What jefrs said with a bit more emphasis on earthing everything.


Without knowing more information it is difficult to be specific, so the fart in a colander method of every direction at once is used. Wink

When the coil acts up it usually does so at high revs because there is less volts then (actually less time to charge). High speed misfire, but there are two coils and they don't both fail at once.

If the sparks are good then it is usually the carburettor, but again why would both go down together.

Something common has to be found.

Then there is the battery. If its volts are low it won't energise the coils well until the alternator spins up and takes over duties.

Look for the simplest cause first. What was changed last? It could just be bad fuel.
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 07 Sep 2018 at 08:23
FFrom what you say I think the coils are wired the wrong way round, though couldn't be sure it matters. Is the advance sticking? Suddenly going full advance at 3k.
Brian.

Better 5 minutes late in this world than years early in the next.
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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 07 Sep 2018 at 15:54
Originally posted by Po51uhd Po51uhd wrote:

The bike runs like a pig and won’t pull under 3000 revs then pulls like a train above that. Tickover is unsteady.

Has it worked properly before? Or the bike is 'new' to you? (So you don't know)



"Chicken nuggets don't dance on a Tuesday."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Po51uhd Quote  Post ReplyReply Direct Link To This Post Posted: 07 Sep 2018 at 21:48
Thanks for all your ideas and suggestions. It IS a new bike to me so I’m not sure how it ran earlier. I bought it as a non-runner.
I’ll be trying some of these and will let you know...
Stephen 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 08 Sep 2018 at 10:28
Following on from Brian's suggestion if the advance is stuck fully advanced it would give similar symptoms.

I don't think coils are too bothered which way round they're connected although there is a theoretical "right" way.
Ian
1982 V50
1952 Norton ES2
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