How not to B33!

[Steve.S]

Is this a typo? I'm not sure that a spark at TDC fully advanced is quite right.
Dan, you need to make sure your magneto spark will jump a gap of around 8mm. No good holding the HT lead with your hand, it will move all over the place. Buy a Spark gap tester or make one, and let us know how big a gap it will jump.
When it won't start when hot, use your tester to confirm a good spark and then move on to carburation, or technique, i.e throttle open or closed, choke on or off, advance or retard etc. But do fit an insulator.

[Derek996]

I think Neil means to set the ignition with the advance/retard lever in the fully advanced position. I'm not sure that I've ever seen a magneto that will manage an 8mm spark gap, certainly not at kick over speed, but 5mm definitely. Coil igniton will give maximum spark at any speed but a magneto needs a bit more wheech.

[neil1964]

Is this a typo? I'm not sure that a spark at TDC fully advanced is quite right.
Dan, you need to make sure your magneto spark will jump a gap of around 8mm. No good holding the HT lead with your hand, it will move all over the place. Buy a Spark gap tester or make one, and let us know how big a gap it will jump.
When it won't start when hot, use your tester to confirm a good spark and then move on to carburation, or technique, i.e throttle open or closed, choke on or off, advance or retard etc. But do fit an insulator.

Sorry I meant at correct reading (7/16" BTDC) on firing stroke

[Dan_B33]

Hello,

Valves clearnce:  set to the book(good compression hot and cold- need to use decompressor or jump full body weight)

Magneto spark:
               cold was easily jumping 6mm on the table with hand twist.
                Hot- nice spark on plug but not tested without spark plugs -tbd.


Timing: rechecked and OK. Nice brownish spark plug after 5 miles ride

Carb / head separator to be changed.


Will keep you posted


Many thanks for all advised solutions


Dan

[Dan_B33]

Ha have installed new separator Carburator/cylinder head.

First tests show promising results.

https://drive.google.com/file/d/10m4PTtAw1IZAEyuyjJjlkpzhHqloAHEB/view?usp=drivesdk

Now I have 8mm isolation.

Lets see how that works in real life.

I have seen big improvement already today.
Bus my skepticism tels me to hold the fanfares.

Da

[Dan_B33]

Hello,
No win! Still the same.
Need to investigate deeper.
Spark is strong .
Idolator fitted
20 kills on Hot engine and spark is not flooded.

No start!

Cold start first kick.

[Steve.S]

So did you have to call breakdown recovery? Bad starting when hot can often be caused by technique. Did you try all the suggestions I made? Leave petrol off, on, throttle open, closed, 1/8 open, alter advance retard etc. etc.etc.
This is a very common problem, and I have the same problem myself, but I think, in my case it's down to technique. Unfortunately it alters every time. It's often due to a weak spark when hot. Did you have your magneto remagnetised? Maybe it's weak magnetism?
You really need to check the length of your spark when hot. Don't bother laying the plug on the head. This threw me once on another motorcycle, as I had a spark at the plug, but when I eventually got home, the magneto was only producing a spark 1/8" long.
Maybe try a different make of plug? What plug gap are you using?

[neil1964]

I presume:
Non-suppressed plug cap
Non-resistor spark plug (what are you using)
Solid copper core HT cable with clean well made end with brass washer at the end that screws into the magneto
Spark plug gap of 18thou
Points gap of 12 thou
You have clean fresh fuel with clean filters (in the tank) and the carburettor is standard spec?
Tappets are set at 3 thou.  The valve lifter is not 'ever so just' tightly adjusted such that it only binds kicks when engin hot?
Your idle mixture is set when the engine is properly warm (not when first started and by time fully warm is is too rich?
No more piston 'nipping up'?
What is the state of your magneto armature and magnet.  I guess the insulation on the armature could be breaking down with high temperature?
After these suggestions (pretty sure that you will have covered them already?) I am out!

[Dan_B33]

I presume:
Non-suppressed plug cap- YES
Non-resistor spark plug (what are you using) YES
Solid copper core HT cable with clean well made end with brass washer at the end that screws into the magneto - YES
Spark plug gap of 18thou- YES
Points gap of 12 thou- YES
You have clean fresh fuel with clean filters (in the tank) and the carburettor is standard spec?- YES
Tappets are set at 3 thou.  The valve lifter is not 'ever so just' tightly adjusted such that it only binds kicks when engin hot?
Your idle mixture is set when the engine is properly warm (not when first started and by time fully warm is is too rich?
No more piston 'nipping up'? - No More!
What is the state of your magneto armature and magnet.  I guess the insulation on the armature could be breaking down with high temperature? Spark is strong alm the time even higher temperature
After these suggestions (pretty sure that you will have covered them already?) I am out!

I'm off almost all summer for vacations and work. Will be back next week to start investing. For now I jus enjoyed occasional ride of 10miles ....and back to garage.

More new soon

[neil1964]

Only thing I cannot find in the thread is how the magneto was rebuilt.
Original Lucas paper condensers do deteriorate and the insulation breaks down leading to mag failure when hot (as does failing insulation on the internal coil.
Did you replace the condenser at time of rebuild. If not an easy fix is the Bright Spark surface mounted Easicap.  You will need to strip the mag end cap to remove the old one.
Maybe you've already done that?

[Dan_B33]

Hello Neil,
Yes that was done and spark is good at any time hot or cold.

My work recently keeps me away.
I take occasional rides on BSA starts first or second kick.

I hope winter will be more relaxed time to dig again deeper to the issue.

Anyway many thanks for the hint

[Dan_B33]

Hello,
Long time no update.
I have fitted today my clutch with talker inner basket. I hah to reinforce inner ring since it was not holding ( as described by you guys). I have asked my friend to weld it.
Now it is perfect. I have added 5th Clutch plate.

Other updates is I have installed stop sensor (Lucas). I have stop light now.

I have installed one way valve on the breather. To maje sure it just exhales.

I have not determined yet root cause for difficult start on hot.


Cheers

Dan

[Dan_B33]

Hello,
BSA makes miles.

My warm starting is a bit better after installing warmer spark plug with longer isolator.

This is in testing phase now.

I plan as well on installing pancake air filter. Any advice on tuning carb to that? Change the main jet?

[limeyrob]

Take it for a run with the filter first then look at the plug colour.  If its OK leave it alone, if its showing rich drop the main jet by 10 and the needle jet one notch and check again.  Hot starting, does it have the tufnol insulator between the carb and head?

[Dan_B33]

Hello, long time no post.
Yes insulator is there.

I have not solved the problem completely.I have made 600km trip this weekend.
BSA bravely cruised 50-55mph.
Gave me no problem at all.
On warm it started usually 2 kick. If not then 10kicks on decompress and it eventually started.

I have installed air filter. Spark.plug looks okay. Slightly reach.

Will fine tune.

Overall bike is running. DVR2 provides good charging. Poland we have 24h lights on obligations.

Cheers

Dan