no spark in situ

[royblackburn1@btinternet.]

Hi all A65L would not start battery was charged up but would not kick over put some ingnition spark testers on each plug (red plastic plug type cap with I think a diode inside goes between plug and cap) tried to kick it up  but the diodes did not flash took plugs out with testers still on rested them on cylinder head kicked it over the testers and plugs flashed tried several times plugs in and out but would only flash on cylinder head bike has boyer ignition and duel coil,strange they would not spark under compression. Any ideas please Roy

[A10 JWO]

I would suggest a test on the battery, you may have low voltage. Boyer have a website that has all the answers on problems like this. Good luck.

[royblackburn1@btinternet.]

Thanks A10 JWO the battery was fully charged, cannot understand why they spark when earthed to the cylinder head but will not in the plug hole, could something be slipping when kicked over when plugs are in situ and causing compression.

[Mike Farmer]

 

Is it the plugs. I had a 'duff' set straight out of the box.

Mike

[A10 JWO]

Some plugs will not spark under compression, something I don't understand but fact.

[johnjag]

Hi - is the engine actually turning over when you are kicking? It might be the clutch slipping under compression.  John.

[royblackburn1@btinternet.]

Thanks for the replies, JohnJag  going to look at clutch after trying  different  plugs the only thing I can think it might be is the clutch. Roy

[royblackburn1@btinternet.]

I know oil should be in the primary chain case but should the driving plates be wet mine are just damp if they should be wet would a soak in oil help.Roy

[royblackburn1@btinternet.]

Hi all, johnjag yes the engine is turning over when kicking but I was like you thinking it might be  the clutch slipping under compression so I put new drive plates in and cleaned the driven plates up but still the same, testers and plugs flash and spark when earthed to cylinder head but not in situ,more help wanted please.Roy

[Mike Farmer]

 

Hi.
I cant be specific about this ---lack of knowledge---But you might just need a plugs with a different power/heat range. Guess you'll need to read that up.

Mike

[royblackburn1@btinternet.]

Thanks Mike not trying to start it at this stage so using new plugs the same as it had when running, just want both plugs sparking when in the holes and under compression

[royblackburn1@btinternet.]

Thanks for your replies sent a E.mail to boyer bransden didn't get a good reply, but still can't get it in my mind how the plugs and testers spark and flash when rested on cylinder head and will spark and flash with one plug and tester in the plug hole but not with both plugs , will have to go to back of shed for a while.Roy

[Jackson]

Just trying to think my way round this. Other posts lead me to believe that Boyer use a wasted spark system. Wouldn't this mean that you would need double the voltage to achieve breakdown across two gaps? If so it would explain not sparking  when two plugs are in and sparking when one is out of the hole. The breakdown voltage is roughly proportional to the pressure times the gap length. So a combination of a wasted spark system and a low voltage from the electronic ignition would explain the behaviour, but not how to put it right. A capacitor failed somewhere?
Adrian

[royblackburn1@btinternet.]

Wow thanks Adrian what a technical reply, way over my head but I get the meaning, going to put it on back burner for a while . Roy

[berniej]

I don't think that the Boyer unit would introduce a problem with breakdown voltage - although it sounds as if the problem could be related to that if the plug sparks under no compression but doesn't under compression as you have found.

The Boyer system is designed to fire both cylinders at the same time (hence wasted spark as one is on exhaust stroke) and does this either using two (typically the original) 6V coils re-wired in series. Each coil still receives a 6V potential across it to fire it (assuming both coils are good and have same resistance) so each should generate a good spark.

The idea behind this I believe was to allow the original 6V coils to be re-used. However, if one is damaged or they have different resistances on the low tension (6V) coils for some reason then this could affect performance as the voltage applied across each coil would be something other than 6V and 6V - e.g. 7V and 5V. This could be checked using a multi-meter to verify that the resistances are the same on each coil.

An alternative configuration is to use a single, dual-output 12V coil instead as commonly fitted to modern twin cylinder bikes. I used this on my last A65 to good effect.

It does sound from your description as if a weak spark might be at least part of the problem. Have you tried swapping combinations of which plug/coil is sparking loose on the head and which tight in the head? That might throw a bit more light on the problem if the problem moves with the plug or coil used....

Cheers,
Bernie