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Stymied on B25 #642194
02/28/16 9:23 pm
02/28/16 9:23 pm
Joined: Feb 2016
Posts: 12
NC, USA
D
DJ Choga Offline OP
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DJ Choga  Offline OP
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NC, USA
Barn find 1970 starfire b25, complete bike. Cleaned up nicely. However I just cant get it started. Brand new battery, installed missing Fuse on -ve battery terminal. cleaned the points. Replaced all fluids. All Lights work now off the battery but I just cant get a spark. Any Suggestions for this mess. Thank you for your help.


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Re: Stymied on B25 [Re: DJ Choga] #642195
02/28/16 9:32 pm
02/28/16 9:32 pm
Joined: Oct 2008
Posts: 1,666
Canada
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LarryLebel Offline
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Does the motor have compression? If you're getting spark the timing could be off. Are you using the choke or the tickler to start it. Does the plug get wet when to try to start it?
Anything is possible.

There's a saying that goes all ignition problems are caused by the carburetor and all carburetor problems are caused by the ignition.

Re: Stymied on B25 [Re: DJ Choga] #642206
02/28/16 11:13 pm
02/28/16 11:13 pm
Joined: Jun 2002
Posts: 921
Jaffrey, NH, USA
Peter Quick Offline

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No spark can be all sorts of things. Bad coil, bad condenser, broken wire somewhere, bad ignition switch, bad spark plug..... (you put in a new plug I presume). Is the spark plug wire plugged firmly into the coil?

Perhaps run a wire directly from the battery to the coil to start off with and see if you get a spark. If you do then the problem lies in the wiring or the ignition switch. Perhaps even run another wire from the motor (alligator clip to a rocker box stud) back to the ground that the battery is hooked to. No spark still? Then consider coil, condenser, wire to the points. Perhaps others will have better ideas.

Peter


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Re: Stymied on B25 [Re: DJ Choga] #642211
02/28/16 11:51 pm
02/28/16 11:51 pm
Joined: Jun 2002
Posts: 9,688
Scotland
S
Stuart Offline
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Stuart  Offline
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Scotland
Hi,

Originally Posted By DJ Choga
All Lights work now off the battery but I just cant get a spark.

Are the points opening and closing as you turn the engine over?

If they are, disconnect the condenser; if you now get a spark, you need a new condenser (don't run the engine for any length of time without a new condenser).

Is the HT lead attached directly to the spark plug under a plastic cover, or is it screwed into something like an NGK plug cap that's then attaches to the plug?

If the HT lead attaches directly to the plug, does the plug end have the waisted screw-on terminal? If it doesn't (thread visible) the HT lead terminal is too big for the plug terminal.

Otoh, if there's anything like the NGK plug cap between the lead and the plug, these can fail.

If all of the above works and still no sparks, time to get the multimeter out ...

The ignition circuit is:-

. battery -ve -> Brown/Blue -> ignition key switch;

. ignition switch -> White or White/Blue -> White -> handlebar kill switch (if fitted) -> coil;

. coil -> Black/White -> points -> points plate -> engine;

. engine -> Red -> battery +ve.

Risking telling you things you know already:-

1. Set the meter to a Volts scale just above 12V, start testing by touching one meter lead on each of the battery terminals and noting the meter reading - should be something above 12V.

2. Test all connections between the coil and the ignition switch by touching one meter lead on the connection and the other meter lead on battery +ve. You should always see the same meter reading as you saw at 1; if you don't, there's a break or Volts drop between the battery and the coil where you see the meter reading change.

3. Between the coil and battery +ve, test all connections by touching one meter lead on the connection and the other meter lead on battery -ve. Again, you should always see the same meter reading as you saw at 1; if you don't, again there's a break or Volts drop between the battery and the coil where you see the meter reading change.

4. If you need to check for continuity between two points not involving the battery, change the meter setting to Ohms and connect one meter lead to each point you want to check between. Only thing to bear in mind is the meter does this check with its own battery, which can provide only a small current. So you might see zero Ohms (good continuity) on the meter but whatever you're testing fails when it has to conduct the 3A-4A drawn by the ignition coil. frown

5. When testing involving a coil terminal, always ensure the meter lead contacts the threaded pillar in the centre of the nut attaching the tab terminal; then the test'll show up any continuity problem between the coil itself and the tab terminal.

6. If you test the coil itself, the meter should show:-

. between 3 and 4 Ohms with one meter lead connected to each threaded pillar terminal (low-tension terminals) on the coil;

. between either LT terminal and the spark-plug lead socket (high-tension) terminal, ~5000 Ohms on a Lucas coil, ~7000 Ohms on a pattern one like a PVL;

. infinite Ohms between any terminal and the case.

Hth.

Regards,

Last edited by Stuart; 02/29/16 1:22 pm.
Re: Stymied on B25 [Re: Stuart] #642215
02/29/16 3:01 am
02/29/16 3:01 am
Joined: Sep 2013
Posts: 1,664
Pacific northwest
Q
quinten Offline
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quinten  Offline
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Pacific northwest

? Sparkplug is out in open air and earthed ?
I know ... but it has to be asked .

Check that the wired-end to the condenser stud , and the spring , are not inadvertently grounded ... its a tight fit in there ... a bit of E-tape against the aluminum housing can work wonders . A plastic shim from a milk jug works too .

Re: Stymied on B25 [Re: Stuart] #642259
02/29/16 12:28 pm
02/29/16 12:28 pm
Joined: Feb 2016
Posts: 12
NC, USA
D
DJ Choga Offline OP
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DJ Choga  Offline OP
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Posts: 12
NC, USA
Thank you for wealth of information
Where is the condensor?
What is HT and LT?
Maybe its time to push it back in the barn...


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Re: Stymied on B25 [Re: DJ Choga] #642260
02/29/16 12:36 pm
02/29/16 12:36 pm
Joined: Dec 2004
Posts: 9,228
Scotland
kommando Online content
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kommando  Online Content
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Scotland
Quote:
Where is the condensor?


On a 70 it is on the frame below the battery tray facing the engine, there should be a black/white wire attached. Its separate from the points plate as you have a 6CA plate and no condensor is on that plate.

Quote:
What is HT and LT?


HT is High Tension and is the high voltage output from the coil that ends up being a spark at the plug eg the HT circuit.

LT is the battery volts and it refers to the wires from the battery to the points and then onto the coil and then earth/battery ie the LT circuit.

Nearest handbook to a 70 is the 69 TR25W

http://www.bsaunitsingles.com/Archives/O...rd%20Ed%20x.pdf

Re: Stymied on B25 [Re: kommando] #642281
02/29/16 2:49 pm
02/29/16 2:49 pm
Joined: Feb 2016
Posts: 12
NC, USA
D
DJ Choga Offline OP
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nothing under the battery box but grime.


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Re: Stymied on B25 [Re: DJ Choga] #642289
02/29/16 3:50 pm
02/29/16 3:50 pm
Joined: Dec 2004
Posts: 9,228
Scotland
kommando Online content
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Scotland
See the silver can behind the red wire, that's the condensor.



So look in the same area, you can see the battery tray supporting studs and the oil pipe.

Re: Stymied on B25 [Re: DJ Choga] #642291
02/29/16 4:08 pm
02/29/16 4:08 pm
Joined: Jun 2002
Posts: 9,688
Scotland
S
Stuart Offline
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Stuart  Offline
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Scotland
Hi,

Originally Posted By kommando
Quote:
What is HT and LT?

HT is High Tension and is the high voltage output from the coil that ends up being a spark at the plug eg the HT circuit.

LT is the battery volts

blush Apologies for the confusion caused by the short-hand; I've amended my post; hopefully it's clearer?

Originally Posted By kommando
Nearest handbook to a 70 is the 69 TR25W
http://www.bsaunitsingles.com/Archives/O...rd%20Ed%20x.pdf

... wiring diagram is riddled with misprints ... crazy

. "Brown/Black" between battery -ve and the fuse should be "Brown/Blue"; the Brown/Black wire is only between the horn and the handlebar horn button (assuming the horn button is original);

. "White/Brown" between "Ign Sw" and the White wires to "Rear Stop Switch", "Front Stop Switch" and "HT Coil" should be either "White/Blue" or just plain "White";

. "White/Brown" shocked between "Dip Sw" and "Headlight Dip Beam" should be "Blue/Red"!

. Not shown on the diagram but present on your bike is another White wire to the red Oil Warning lamp on the headlamp shell, the wire from the warning lamp to the switch on the engine is White/Brown ... whistle

Hth.

Regards,

Re: Stymied on B25 [Re: Stuart] #642295
02/29/16 4:26 pm
02/29/16 4:26 pm
Joined: Sep 2013
Posts: 1,664
Pacific northwest
Q
quinten Offline
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Pacific northwest
Here is a simplied coil ignition wiring diagram .
This one is positive ground . (Notice) , it does have some
Missing or (implied) connections
(The condenser and points should also show individual ground connections)

....
This second digram is more complete , but notice , it is negitive ground .
....

Also notice , the 'points'-condenser can be placeed 'anywhere' ,
In parallel ,
On the 'wire-path'
from the coil to the points .

... SO look for a second wire connected to the coil ... on the side of the coil the
Goes to the points .

Re: Stymied on B25 [Re: DJ Choga] #642379
03/01/16 8:12 am
03/01/16 8:12 am
Joined: Aug 2001
Posts: 3,881
Cape Carteret, NC
M
Mr Mike Offline
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Cape Carteret, NC
Hey,
I see you are from NC. I'm here too. It's a big state but maybe we aren't too far away. I've got a few BSA's running over the years....know most of the ignition and carb tricks.

Mr Mike

Re: Stymied on B25 [Re: Mr Mike] #642783
03/04/16 1:06 am
03/04/16 1:06 am
Joined: May 2015
Posts: 40
California
K
KEEFYWARD Offline
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Posts: 40
California
I had a weird no spark episode on my B44, the new contact breaker was sliding off the brass pin and shorting out on the chrome points cover; when I took the chrome cover off I got a spark, put the cover back on - no spark. just a weird fault in case all else fails

Re: Stymied on B25 [Re: Stuart] #643519
03/09/16 12:09 pm
03/09/16 12:09 pm
Joined: Feb 2016
Posts: 12
NC, USA
D
DJ Choga Offline OP
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DJ Choga  Offline OP
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Posts: 12
NC, USA
Thanks. Here is what I got so far:

Test 1. 12.54 V
Test 2. 12.54 V on terminal with Brown/white wire. 0 V on other 2 terms.
Test 3. 0 V

Something with the coil then? Now what?

Thanks for the help.


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