Mark3 won't fire

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Pete Mahone

Pete Mahone

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Oct 20, 2017
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G'day All,
I recently purchased my Mk3, my first ever British bike.
I bought it from a bloke who imports them from the U.S. And passed it over to a Brit bike "specialist" to get it ready for registration. I have no history on the bike.
She has been running sweet, starting first or second kick (or push of the button)
Until a week ago, she died while I was on a short ride.
The ignition light stayed on, but wouldn't fire.
I brought her home in my van, got her out and she fired up first kick.
I read everything on the subject on this forum, pulled the right hand switch cluster apart, cleaned it and found the spring holding the killswitch contact in place is rusted and broken. After reading more on this forum, I decided to bypass the switch.
I soldered the WY wire to the White inside the light as suggested in a post.
The ignition light still comes on, the electric start is spinning the motor well but she won't fire. Can anyone tell me what my next steps should be please? She has points and what looks like the original coils.
Many thanks,
Pete.
 
Pete Mahone said:
The ignition light still comes on, the electric start is spinning the motor well but she won't fire. Can anyone tell me what my next steps should be please? She has points and what looks like the original coils.
Click to expand...

Have you checked for sparks with the plugs removed (plug bodies touching the cylinder head)?
 
If it isn't a wire/connection fault then perhaps the ballast resistor has failed (if no sparks).
 
Pete Mahone said:
G'day All,
I recently purchased my Mk3, my first ever British bike.
I bought it from a bloke who imports them from the U.S. And passed it over to a Brit bike "specialist" to get it ready for registration. I have no history on the bike.

I read everything on the subject on this forum, pulled the right hand switch cluster apart, cleaned it and found the spring holding the killswitch contact in place is rusted and broken.
Click to expand...

That doesn't sound very "specialist", it sounds more like the usual U S import where the minimum is done to get it out the door for maximum profit.
I would suggest going over the bike, what does die on a ride mean, just stopped, missed, sputtered, lost power etc ?

Old motorcycles, pick one. :D

The one that has been gone through for reliably.
The one that will be gone through for reliability.
The one where you hope for the best.
 
Hi,
After about 10km, lost all power and rolled to a stop. No sputtering or misfiring. The engine just stopped firing.
It happened a few days previously, after about the same amount of riding.
I thought that I might have had a vapour-lock because I opened the fuel tank, kicked her over and she started.
I ran a small drill bit (by hand) through the breather on the tank cap when I got home.
 
Stopping after the same distance is either fuel starvation from blocked tank breather or an electrical component is taking a set time to heat up and then stopping working. Sounds like it was the tank breather but if it happens again then start checking electrical items, what ignition is fitted ? I had a Boyer where I fitted a 3 ohm twin coil but it tested as 2.9 ohm, on hot days it overheated after 20 mins and no sparks, changed it to a pair of 1.7 ohm coils in series so 3.4 ohm and 5 years later never had another stoppage.
 
Pete Mahone said:
After about 10km, lost all power and rolled to a stop. No sputtering or misfiring. The engine just stopped firing.
It happened a few days previously, after about the same amount of riding.
I thought that I might have had a vapour-lock because I opened the fuel tank, kicked her over and she started.
I ran a small drill bit (by hand) through the breather on the tank cap when I got home.
Click to expand...


Do both carbs still flood within a few seconds when the ticklers are operated (assuming they did before this problem occurred) as fuel starvation would be less likely the cause of the non-starting (but not perhaps extended running).

kommando said:
what ignition is fitted ?
Click to expand...

Pete Mahone said:
She has points and what looks like the original coils.
Click to expand...
 
Last edited:
If the ballast resistor had failed then the engine should try to start when the electric starter is turning but would die immediately the starter button was released so unless that's happening it's probably not a failed ballast resistor.
 
Hi Pete, a similar case was discussed here in this forum in the last year. Turned out to be defective coils. Do a search here. I bet coils are at fault in your case as well. If the primary coil fails in one, they will both fail as they are wired in series (assuming you have stock 6V coils and the ballast resistor). If shot or not, if they are the stock ones (Lucas MA6) they are ripe for replacement, as are the condensers and breakers. While you are at it, replace the HT wires and caps as well.

The other fault could be debris in your petrol tank and carburettors. However, with debris you would have a sputter rather than a sudden cut-off.

Good luck!

-Knut
 
mdt-son said:
If the primary coil fails in one, they will both fail as they are wired in series (assuming you have stock 6V coils and the ballast resistor).
Click to expand...

The standard points ignition with ballast resistor the (6V) coils are wired in parallel.

Mark3 won't fire



mdt-son said:
If shot or not, if they are the stock ones (Lucas MA6) they are ripe for replacement,
Click to expand...

The stock coils are Lucas 17M6.
 
Yep, stock dual coils are wired in parallel, most (all?) electronic ignitions change them to be wired in series so they "become" a single 12V coil firing a wasted spark instead of two 6 volt coils firing individually.
 
I stand corrected. If coils were wired in series, there would be no need for a ballast resistor - my short! As for type of coil, 17M6 is correct, superseeding MA6 from 1968 onwards and being of smaller diameter (41.3 vs. 48 mm).

-Knut
 
Last edited:
G’day all, thanks again for all your input.
So....., I’m feeling really stoooopid right now. I just worked out why she wouldn’t fire, when I went to bypass the killswitch, I stripped some of the grey outer sheath away to expose the white wire and then cut and soldered the WY to it. Trouble was, I soldered the end that is running to the swithblock. Arrrgh. I soldered the correct end and she started first kick.
Sorry to waste your time.
It’s pouring rain in Brisbane today so I won’t get a chance to check if it stops after about 10k’s again.
I really appreciate all of your time and input. If the problem continues I’ll know where to start looking.
Thanks again,
Pete.
 
Pete Mahone said:
G’day all, thanks again for all your input.
So....., I’m feeling really stoooopid right now. I just worked out why she wouldn’t fire, when I went to bypass the killswitch, I stripped some of the grey outer sheath away to expose the white wire and then cut and soldered the WY to it. Trouble was, I soldered the end that is running to the swithblock. Arrrgh. I soldered the correct end and she started first kick.
Sorry to waste your time.
Click to expand...

:)
Not to worry. Good to hear you've got it sorted out.
 
Hi Pete, I'm over here in Samford, Interstate 750. Give us a bell if you're coming out this for a ride. 32891699
 
Don't worry Pete its all a learning curve for you and your new to you bike, we all make mistakes even the experts make mistakes sometimes, at leese you admitted your mistake and its normally the simple things we make mistakes with, when your ready bring your Norton over and we pull your clutch plates out and give them a good clean and fix your sticking clutch.

Ashley
 
Pete, thanks for letting us all know (often people don’t).

As this is your first Brit bike, your problem solving will likely get much sharper in years to come as the bike provides ‘opportunities for problem solving practice’.

And, for some reason, we all break the basic rules which are:

1. Always look first at whatever was changed / interfered with / worked on / ‘improved’ last.
2. Always check the simple, basic stuff before looking at anything complex.

Its far too easy to jump to the conclusion that our EI is toast when it’s just a duff plug, or our carb is faulty when we’ve just run out of petrol!

Or is it just me...!?
 
Fast Eddie said:
Pete, thanks for letting us all know (often people don’t).

As this is your first Brit bike, your problem solving will likely get much sharper in years to come as the bike provides ‘opportunities for problem solving practice’.

And, for some reason, we all break the basic rules which are:

1. Always look first at whatever was changed / interfered with / worked on / ‘improved’ last.
2. Always check the simple, basic stuff before looking at anything complex.

Its far too easy to jump to the conclusion that our EI is toast when it’s just a duff plug, or our carb is faulty when we’ve just run out of petrol!

Or is it just me...!?
Click to expand...

Yep fully agree with FE and its not just you we all make mistakes like that, how else do we learn.

Ashley
 
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