Ran well, now doesn't

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michael95453 said:
Thanks. I have been suspicious of the Boyer box. No, I don't have one to swap out. If it comes to that, I'll look into a Mk 4.
Click to expand...

My memories of the phenomena that I experienced are returning to me slowly - LOL!!

A test for this would be, while riding in 4th gear, to approach the rev range where this happens (~2500 RPM). Once there, downshift to 3rd gear, and accelerate to about 4000-5000 rpm - assuming the speed limits allow that sort of speed. Up shift to 4th again so that you are above the RPM that it occurs at. If you have smooth operation above 2500-ish RPM range, then you likely have found your culprit.

When I did this, I found that I had another "dead spot" at about 3500 RPM, so I had to keep experimenting with shift points to try to keep out of these two areas.

I am shying away from it being a broken wire issue. Usually with broken wires, operation is totally unpredictable, where as you have described a condition that occurs consistently at the same engine RPM range - at least from what I read - correct me if I am wrong.

FWIW
 
To clarify...I can't even get out of 1st gear. I'm riding around my neighborhood with it bucking and popping. Applying more throttle causes it to bog down, but it won't die, it will always idle. It is consistent in its symptoms, and like I said, it came on when I was a few miles from home and had to limp it home.

I can get it to rev up with some hesitation when at a stop, but it won't rev up under load.

I will be checking ignition timing later today (just got up here in California). It seems like it isn't advancing, but I'll find out what it IS doing.

I really appreciate everyone thoughts and suggestions!
 
Might be a blocked tank breather - creates a vacuum in the fuel tank and stops fuel flow to the carbs ? Changing ignition timing or comp. ratio, or altering the exhaust system can create the same symptoms as altering carburation.
Sometimes the tank breather is a hole under the tank cap, and the rubber seal can move and block it.
 
I confirmed my broken wire by giving a few tugs on the wires whilst idling.
 
Check the trigger wires haven't been accidentally swooped round. From memory which is getting worse, if they are you'll get a spark but no advance.
Dave
 
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Update: Started the bike to warm it up to check the timing. Tried moving/pulling on the wires on the Boyer stator plate and the bike started sputtering and died. Repeated multiple times. Took the stator plate out and found intermittent continuity on one of the wires (no visible break). I'm in the process of installing posts/ring connectors in place of the soldered wires. Haven't finished, but will update again after I get it back together and set the timing. Hopefully, that is THE problem.

Also sprayed contact cleaner around the intake manifold to check for air leaks...nothing obvious.

Thanks for all the help and suggestions.
 
If it isn't the Boyer wiring, take the carburetor and intake off, check all the parts, get whatever gaskets you need, and reassemble. Hair line cracks/leaks in the rubber boot or leaks between mating surfaces would be enough to cause the motor to misfire under load, and not show up when sprayed with flammable liquid externally. That spray stuff will ruin the paint on your frame BTW. I never use it for troubleshooting. I either take things apart and check them and reassemble, or retorque everything. With a Norton, it's usually all of the above.

I'm pulling for ya. You'll get there.
 
michael95453 said:
Update: Started the bike to warm it up to check the timing. Tried moving/pulling on the wires on the Boyer stator plate and the bike started sputtering and died. Repeated multiple times. Took the stator plate out and found intermittent continuity on one of the wires (no visible break). I'm in the process of installing posts/ring connectors in place of the soldered wires. Haven't finished, but will update again after I get it back together and set the timing. Hopefully, that is THE problem.

Also sprayed contact cleaner around the intake manifold to check for air leaks...nothing obvious.

Thanks for all the help and suggestions.
Click to expand...
I am still using a '70's vintage Mk IIa Boyer pickup plate - the one with the terminal block attached to it. Knock on wood, I have yet to have a problem with it, so hopefully the modification you are doing is equally as successful
 
Derek Wilson said:
I am still using a '70's vintage Mk IIa Boyer pickup plate - the one with the terminal block attached to it. Knock on wood, I have yet to have a problem with it, so hopefully the modification you are doing is equally as successful
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I used to use this screw on type Boyer pickup
I don't believe they suffer the same fate from vibration as the permanent wired in wires
 
Just for grins: I'm not saying it isn't the Boyer or any of the other troubleshooting hints that usually come up here, but like Derek with the earlier Boyer, I've never had a problem with the later MkIII Boyer either. If ya don't count kick back.

That being said, I would not put another Boyer ignition on my motor if mine quit working. That stator plate looks like something than came out of a 1950's portable handheld radio. If I wanted another inexpensive basic EI, I'd get the Vape Wassell, since it looks more robustly designed for vibration and environmental conditions. If I wanted something with more features I'd never use, I'm not sure what I would do.
 
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Blue header pipes indicates late timing, which is burning fuel in the exhaust ports, rather than in the cylinders. That results in poor power also.

Slick
 
michael95453 said:
Update: Started the bike to warm it up to check the timing. Tried moving/pulling on the wires on the Boyer stator plate and the bike started sputtering and died. Repeated multiple times. Took the stator plate out and found intermittent continuity on one of the wires (no visible break). I'm in the process of installing posts/ring connectors in place of the soldered wires. Haven't finished, but will update again after I get it back together and set the timing. Hopefully, that is THE problem.

Also sprayed contact cleaner around the intake manifold to check for air leaks...nothing obvious.

Thanks for all the help and suggestions.
Click to expand...
That is THE problem.
 
concours is right! That was THE problem. I put it all back together and took it for a short ride and it runs as beautifully as ever.

All the problems I've had on this bike in 2+ years have had to do with vibration-induced wiring issues. Go figure!

My biggest regret is that my previously beautiful chrome exhaust pipes are now discolored. I guess I could call it patina. Anyone have suggestions for a supplier for new Mk3 unbalanced pipes?

Again, thanks for all the help!
 
You must use the MK1V Boyer with your Mk 111. That said , check to see if the needles have not popped out of their grooves and of course fit brand new plugs.
 
“All the problems I've had on this bike in 2+ years have had to do with vibration-induced wiring issues”

Generally speaking, wires need to be PROPERLY supported, tied, lazy looped, allowed to move.
Mostly, previous tinkering by unknowing hands will create the failure area.
 
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