No Spark

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RichFowell

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Good afternoon all
I have a 85 VMX12N. I will try to keep this short whilst giving as much background as I can
This bike belonged to my father who sadly passed away some years ago. The bike has been stood for 17 Years in a garage that unfortunately had no heating during the winter months.
What I have done so far:
The CDI box was sent for testing & found to be unserviceable. This was replaced with a brand new Dynatek 3000 D3K7-7
All relays replaced for know working units except the "Indicator Relay" (Starter Cut Off) as Yamaha call it. This was replaced with a new OEM unit
All wiring connections checked/cleaned. (including earths)
All wiring continuity checked & found to be ok.
Pick-up coils checked as per the manual & found to be spot on given values
All coils removed, checked & new leads fitted.
Low oil warning light comes on when cranking. (Think this was a test to show the bulb was working)
Black/White wire disconnected from side stand relay (just incase)

Now the strange stuff that happend
The Dynatek illuminates correctly when ignition is turned on & the green light flashes to indicate that it is receiving the single from the pick up coils when the engine is being cranked, but no spark is being produced at any cylinder.
I accidentally left the battery totally disconnected from the bike for a week. Reattached the battery, hit the starter & it fired straight up. It was running rough, but I put that down to the carbs not having any maintenance for so long. Turned the bike off & restarted it. Did this 4 times. On the 5th try nothing. On further investigation there is no spark again.
Another week went past before I could get back to the bike (it's in my mum's garage). Again I found that I had left the battery disconnected. Reconnected it & it started up again on the first try. Again as before I turned it off & restarted it. No problem I thought until the 6th attempt this time. No spark & one very frustrated bunny.

I have double & triple checked everything & still can not pin down this issue. If the battery is left connected there is no spark regardless of the time the bike is left to stand.

Any help or advice would be very much appreciated.

Many thanks
 

Fire-medic

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That does sound like an ignition box issue, but someone more-knowledgeable than I will need to give you the advice.

I have the older DYNA with the dip-switches, and it's working fine by me. I hate to say-it, but replacing the unit with the OEM 1985-'89 unit, or the proper DYNA unit, to see what happens is about all I can recommend.

What kind of voltage reading do you get at the starter solenoid and at the battery, when it stops cranking?
 

02GF74

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No spark means you are pulling out the lead onto a spark plug outside the engine and seeing no spark jump across the gap.

I ask this as after I left mine standing for 6 months it would start up run for a few seconds then stop. Do this a couple of times it would not start at all. This was due to blocked pilot jets. So to rule out spark or carb issue.
Standing as long as yours has, carb strip down is almost unavoidable.

BTW there are online spark testers, you could try those (I keep meaning to buy a set)

Also can you check you are getting voltage on the input to the coils, ideally you want an oscilloscope for that. Although you should see an average voltage when engine is running, 12 v when powered, 0v when off and depending g on dwell angle, probably 3-9 v (at a guess), if you always see 0 v, then ignition module RIP

Hace you checked electrical connections are good, in particular the earth leads making good contact.

Are plugs OEM spec NGK.

BTW where are you located?

After you've had it running, you stop and then try to start it again and it won't, will it start if you disconnect battery and immediately reconnect it

Is engine fully up to working temperature when the starting fails

Insert ? after all questions.
 
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RichFowell

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Many thanks for the replies

Fire-medic.
Thanks for your reply. I am getting/got 11.9 at both after cranking, probably because I am using a car battery with leads I made up (not jumper leads). Didn't want the added expense of buying a new battery until the bike is ready to go back on the road.

O2GF74.
Thanks for your suggestions.
Spark Plugs are Brand New NGK DPR8EA-9. I am in the strange position of owning two timing lights & that is what I'm using to test for the spark. I do front cylinders together, then the rears. When it runs, both timing lights are firing.

The voltage at the coils is 0 when ignition is off (or kill switch off) just above 12v at ignition on. I do not have an oscilloscope, but I have checked the voltage to coils whilst cranking (think it was the orange & white wire to each coil) as I wanted to make sure there was enough to fire them whilst cranking. When cranking it was between 8.7 & 9.3 volts.

All connections have been double checked, especially the earths that were taken off & cleaned.

Now you've said it "will it start if you disconnect battery and immediately reconnect it" I have never tried that :mad:. Each time it has started is when it has been stood for at least a couple of days disconnected.

I have not run the engine up to normal working temperature yet, but had resigned myself to doing a rebuild/overhaul of the carbs.

Thanks for looking into this. The bike is located in Leicester in the UK.
 

02GF74

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Interesting what you say about the battery. After 17 years of standing, the bike battery is very likely dead.

Do you have the car battery in parallel with the bike battery or on its own?
What is battery voltage with ignition on? And same when running? When cranking the voltage will drop approx 10 V is the figure stated but since you have car battery, it should drop less - is the car battery in good condition and how many Ah?

Have you had to recharge the battery once it was disconnected?

A car battery will have 4x the capactiy of a bike battery - I'm wondering if that can cause an issue (draw too much current to charge it once bike is running) ; I would suggest fit the battery specified, charge it fully, clean the carbs and try again.

BTW you are about 120 miles away from me,
 

02GF74

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OK, I'm a bit stumped.

You have just the car battery connected or is the old one fitted and car battery used to jump start it?

What is voltage with ignition on?
And again when engine is running?

(I'm over a 100 miles away unfortunately)
 

MaxMidnight

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What need to be established is why it will start once the battery has been disconnected/ re connected.
With the ignition off is the ignition unit still getting 12v; I would assume not?

That it will run (agree with your assumption about the poor running) for a time before it stops sparking suggests that the basic systems are working. It makes me think that there is an internal issue with the Dynateck once it heats up. With zero voltage i.e. battery disconnected it settles down again and will work.

This is a similar issue that some OE units also exhibit which will work when cold but fail as things heat up.

I would try to beg, steal or borrow an OE ICU and see if that sorts the problem.

You don't say if you have checked the pick-up coils.

Using a larger capacity battery wont cause any issues it will still deliver the same voltage.
It is a bit like fitting a bigger water tank with the same outlet hole - it still delivers the same amount of water but can do so for longer.
 

DreamV4

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It is hard to believe but my bike has 4 bad coils. I got replacements already.
Spark problem is diagnosed with multi tester, it doesn't takes much brain, pretty simple. Did you read manual?
 

02GF74

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What need to be established is why it will start once the battery has been disconnected/ re connected.

This is a similar issue that some OE units also exhibit which will work when cold but fail as things heat up.

It isn't just about disconnecting /reconnecting the battery but there is a long gap between the two events, which would have allowed any heated electronic circuits to cool. Hence my suggestion above of disconnecting the battery, then reconnecting it. Also do that but with a 30 seconds gap in between.

Using a larger capacity battery wont cause any issues it will still deliver the same voltage.

It is a bit like fitting a bigger water tank with the same outlet hole - it still delivers the same amount of water but can do so for longer.
Reason why I asked about the battery was that the larger capacity, (larger bucket) to fill it up would draw more current from the regulator /rectifier so these components would get hotter and then cut out, my original post before editing stated that but I deleted it as even if the battery was not being charged, it should supply enough power to keep the engine running for a considerable length of time.

My current thoughts are that something has got hot and then cut out.

Incidentally, once it fails to start, can you try squirting some petrol or carb cleaner into the carbs to see if it fires? I cannot help feeling it is a carb issue even though you have checked the spark - I still would like a lead pulled off onto a spark plug to see the spark or not, to eliminate the tester.

Also have you touched the ignition unit to see how hot it is when it fails to start?
 

MaxMidnight

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It isn't just about disconnecting /reconnecting the battery but there is a long gap between the two events, which would have allowed any heated electronic circuits to cool. Hence my suggestion above of disconnecting the battery, then reconnecting it. Also do that but with a 30 seconds gap in between.

My current thoughts are that something has got hot and then cut out.

Incidentally, once it fails to start, can you try squirting some petrol or carb cleaner into the carbs to see if it fires? I cannot help feeling it is a carb issue even though you have checked the spark - I still would like a lead pulled off onto a spark plug to see the spark or not, to eliminate the tester.

Also have you touched the ignition unit to see how hot it is when it fails to start?

That isn't what I was saying - what needs to be established is if is the removal of any power in the system that allows the unit to work or if it is heat related when the unit is powered that causes the lack of spark.

Given that the other parts of the ignition system are duplicated (pick-up coils) or quaducated (if there is such a word) - coils/ leads/ caps and plugs I would have thought the odds on them causing a total lack of spark is pretty remote; misfire yes but you would expect some signs of life.

I too of the opinion that it is a heat related issue.

IMO if it was fuel or carb related then I doubt that it would be intermittent and associated with power in the system. That said, it would be worthwhile checking that there is fuel in the float chambers when it wont start.
 

RichFowell

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First, thanks for all the replies & apologies for not replying yesterday. I was at work.

O2GF74
The original battery was toast. I am using a 45Ah car battery. The leads are clamped to the battery & bolted to the original positive & negative leads on the bike. The battery is on a battery tender when not in use.
I have never measured the voltage at the battery, only at various points on the bike.
12.3V at Ignition & coils when ignition turned on, this dropped to 8.75 - 9.3 (measured at coils) when cranking.

MaxMidnight
The ignition unit is only receiving power when the ignition is on & kill switch in run position. I have felt the Dynatek box afterwards (only because I was checking the connections) & it does not feel hot, it's barely warm.
Pick-up coil resistance was tested at the first connector (just underneath the starter relay) & at the connection to the Dynatek box. Found all to be well within the specified tolerances.

DreamV4
I have checked the coils. Both the primary & secondary windings are all exactly what the manual says they should be. All coils have been removed from the bike, cleaned, inspected & had new leads fitted before refitting to the bike.


I am starting to believe that there is an issue with the Dynatek. Unfortunately I can not get back to the bike until Thursday due to work.
I'm going to contact the vendor & see if I can return it for testing & whilst waiting I can remove the carbs & do a rebuild & get the correct battery ordered.

Once again thank you so much for all of your input & hopefully can update you all on Thursday evening.
 

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