BSA Bantam misfire and sparking pionts.

[nickjaxe]

Hi guys...still trying to get this my first ever bike back on the road.

To it for a test ride last weekend...spoilt by a bad misfire the bike was jumping with it and didnt like high RPM.

When I took the points cover off and ran the end I could see constant blue sparking at the contact faces on the points.

I thought I need a need condenser...it came today...fitted it...no better still sparking visible even in day light.

Its a very easy starter as well.

And Ideas guys its a B175 Bantam.

[R]

Hmmm, new condensor and points still spark.

All I can think of, is is the condensor actually in the circuit.
It hasn't accidentally been isolated or insulated somehow ?

[nickjaxe]

You always wonder with these things...is the new one ok...not easy to test with out a know good one...you idea has made me think of running some temp new earth to the engine...at present it relies on just the bolt that bolt it to the frame.

Nick.

[Rex]

What you need to do is to look at another bike to see if your sparking is "normal".
The capacitor you bought wasn't a BSA NoS item, was it? They don't last forever regardless of whether they're being used or not.

[nickjaxe]

Hi Rex...no it wasn't...made in Italy...no idea how old...looks new.

I will get another one...no choice...got call re asking other owners...dont know any personalty...but I can ask online.

Tried all sort with it today..even hot wired the coil to cut out the wiring and switches.

Nick.

[mark2]

does the bike tick over nice and even , and miss fire when its rev ?

[nickjaxe]

No even at idle speed its missing...and lumpy...sounds like its going to stop sometimes.

Took the carb off as well...going to give that a good going over in case I am barking up the wrong tree...its a new one fitted by the PO so I left it alone.

Nick.

[nickjaxe]

A second new condenser fitted all fine now...no sparking at the points and the motor run very sweet.

Condenser is made in England.

Nick.

[Akat]

This is a very good example of a new part is not always a good part. I don't know how many times I've heard "I replaced that so that can't be the problem". In over 50 yrs. of working on engines I've learned not to take anything for granted. I could come up with a long list of new parts that were faulty. Also included here are electrical components that test good but fail in use. If a part is suspect but tests good I like to replace it with a known good part like from a good running engine and see if that cures the problem. Process of elimination. Find out what's wrong  by finding out what isn't wrong.

[chaterlea25]

Hi All,
There was a small gizmo that used to be sold for Bantams replacing points and condenser
It was named "Atom",
Bantams commonly have play at the end of the crank that effects the points gap /ignition
it had two wires, if no spark connected one way then reverse the connections,
I fitted one to a lawnmower engine way back, simple and effective
Similar to this unit on fleabay
http://www.ebay.co.uk/itm/Replace-Points-Condenser-Ignition-Unit-Fits-Many-Lawnmower-Chainsaw-Etc-/361466334252?hash=item5429128c2c:g:eKcAAOSw-W5UsZYy

HTH
John

[nickjaxe]

Hi John...interesting....hard to see though how the timing is set as the points running on the cam are not in use any more.

[chaterlea25]

Hi Nick,
I believe the unit sences current and then "trips" when a set value is achieved
This provides the current collapse in the coil primary same as the points opening
With flywheel mags the points should open when the coil poles are lined up with the magnets
I dont know which  electrical principals are used in the unit ??

John

[33d6]

The Atom came in a variety of colours and each colour had slightly different characteristics to suit a variety of engines but there were limitations. For example they would work on early Villiers that only had a two pole magneto but were not recommended for later ones with four and six pole. In essence they worked well in a simple flywheel magneto for ignition only but didn't cope with those made more complex to include lighting duties as well.
I think I still may have a brochure around somewhere.
Cheers,