Sherpa T Mystery

[kramit]

Certainly a mystery, especially as Bultaco's are most often 1 or 2 kick starters with certainty when properly setup.

Did the engine not even fire when you put a little fuel down the plug hole?

Wayne....

This is a great test which usually produces some result unless you have no Ign Spark at all. If the Ign spark is weak at cranking speed, don't ignore the spark plug cap or wire as a problem.

[stork955]

Gday, 2.5 ohms sounds right for a source coil. Remember you are really checking the length of a strand of copper wire. Much higher and there is a break, any lower and there is a short circuit. Also make sure there is no circuit to ground, unless the coil grounds from one end, in which case you are doing that anyway. (Hope that makes sense :-)

Cheers,

Stork

[motovita]

Well I've struck out at getting a source coil in time for the weekend. Oddly, I'm quite dissapointed that I have to ride the modern bike now. At this point I clearly have an open source coil. It did not test that way when I started my troubleshooting and it shows no signs of damage. I hope thats my only problem. Next week I'll order a source coil. condenser and crank seals. Hopefully I'll be back on two shocks soon. I'll let y'all know.

[john collins]

Hi Motovita

While you are checking many of the obvious things

[motovita]

Thanks for the reply. I assure you I went through the simple circles before I entered the complicated circles I'm in now.

I believe (I'm not sure I know anything anymore) I've eliminated the source coil as a possible problem. It was testing open because of minor damage at the connection to the black wire at the points, easily repaired. I ordered a new one anyway because the wiring method doesn't match anyone's description of what it should be. Upon testing the new source coil and the existing one in the bike I find that although they are wired differently they are functionally identical.

The new coil is exactly as you describe with a red, green and black wire. The existing coil has only a black and a green, BUT the green is functionally identical to the red (1.6 ohm resistance) on the new coil and the old coil is grounded directly to the stator plate. The only different effect this has is that I can't set timing with a test light unless I isolate the source coil from the stator plate. I can however check point opening with an ohm meter since the resisitance of the primary coil can be measured when the points open ( 2.1 ohm). Grounding the green wire on the existing coil makes the spark at the spark plug very weak and erratic.

I'll describe the wiring of this bike in hopes that someone can give me more input or suggestions. Keep in mind that this bike ran well for several years wired this way.

There is no terminal block. The wire from the points runs to a large Mallory brand condenser (.36 mfd) mounted to the frame next to the secondary coil. For some reason there was a parallel brown wire fitted from the points to the condenser (I've removed it). The green wire from the source coil, as well as the yellow wire from the lighting coil are taped off and insulated. The small wire from the secondary coil is connected to the condenser along with the black wire from the points along with a wire to a grounding kill switch.

The bike died while riding. It always had spark at the spark plug. When I removed the condenser I found the case was cracked, making it suspect. I replaced the condenser with a common automotive one rated at .18-.25 mfd. I get a healthy looking spark at the spark plug but the bike will do no more than pop.

At this point I have ordered another Mallory condenser rated at .36 mfd, although I've been told by many people that that will make no difference, I don't know what else to do.

Any and all input is greatly appreciated. I can't help but think that there is something I'm missing.

[kramit]

Try this.....

Scribe a line on the flywheel and a corresponding mark on the case.....TDC. Remove spark plug.......rear wheel off the ground. Connect a Inductive pickup ( attaches over spark plug wire) timing light. Connect timing light leads to 12V Batt.

Have a friend turn rear wheel........You will get an idea of your spark signal at kick speed and also a rough idea of you timing setting.

You can get exact timing reading if your timing light has an advance setting indicator.

Most auto shops have this style timing light if you know a mechanic.

[motovita]

Try this.....

Scribe a line on the flywheel and a corresponding mark on the case.....TDC. Remove spark plug.......rear wheel off the ground. Connect a Inductive pickup ( attaches over spark plug wire) timing light. Connect timing light leads to 12V Batt.

Have a friend turn rear wheel........You will get an idea of your spark signal at kick speed and also a rough idea of you timing setting.

You can get exact timing reading if your timing light has an advance setting indicator.

Most auto shops have this style timing light if you know a mechanic.

I've thought of this. My timing light is at another house 200 miles away right now, but I'll get it. The big question is what do I do if I find that the timing is off?

I have approximated the location of the timing window and eyeballed the spark at the spark plug. To my eyes it looks about the right time but I would like to verify it with a light. And yes the flywheel key is fine.

Edited September 25, 2009 by motovita

[kramit]

I've thought of this. My timing light is at another house 200 miles away right now, but I'll get it. The big question is what do I do if I find that the timing is off?

I have approximated the location of the timing window and eyeballed the spark at the spark plug. To my eyes it looks about the right time but I would like to verify it with a light. And yes the flywheel key is fine.

I am sure someone can give you exact details but I believe the points should break 2.5 mm BTDC. You can also scribe a line for this measurement to verify with the timing light, but you need a spark plug hole mounted dial indicator to find this location on the flywheel.

Anything close to TDC should at least start the engine.

PS

Any condensor should work. We used to use one out of a '75 Honda Civic as it was small and would fit easily near the coil. We would mount 2 in case we had one fail, you would just switch the connectors which would hang down near the spark plug cap. This would save having to pull the tank. If you go through all this trouble, I promise you will never have a condenser fail.

[nigel dabster]

Try this.....

Scribe a line on the flywheel and a corresponding mark on the case.....TDC. Remove spark plug.......rear wheel off the ground. Connect a Inductive pickup ( attaches over spark plug wire) timing light. Connect timing light leads to 12V Batt.

Have a friend turn rear wheel........You will get an idea of your spark signal at kick speed and also a rough idea of you timing setting.

You can get exact timing reading if your timing light has an advance setting indicator.

Most auto shops have this style timing light if you know a mechanic.

what is described above by john collins is much simpler and the easy way to do it. He has worked on Bultacos for 40 years so knows his stuff with this make.

[martinm]

Sounds a bit basic, but are you still trying to start it on the kickstart or have you tried push starting it ???

I have an 82 Husky Enduro, it has a motoplat ignition, if left for a few weeks there is no way it will start on the kickstart, you cant turn the motor over quick enough or long enough to get it to fire. Push it 50 metres down the road and it fires up straight away, and when warmed up is no problem to kick.

Worth a try

Martin

[motovita]

Yes I'm kicking it. It never took more than two kicks before. Push starting a Trials bike is much more dificult than an enduro bike because of the high pressure caused by the low exhaust port height, and heavy flywheels. Try it on your rev and you'll see what I mean.

Edited September 26, 2009 by motovita

[b40rt]

Push it 50 metres down the road

Martin

And if it doesnt start, push it 50 m back up the hill

[swooshdave]

If I have a Bultaco that doesn't start with a couple kicks the first thing I do is pull the carb and clear the pilot jet. Even if it looks clear. 95% of the time that does it.

[nigel dabster]

If I have a Bultaco that doesn't start with a couple kicks the first thing I do is pull the carb and clear the pilot jet. Even if it looks clear. 95% of the time that does it.

I always look at the points before the carb, bings set up right last a long while untouched.

[nigel dabster]

Yes I'm kicking it. It never took more than two kicks before. Push starting a Trials bike is much more dificult than an enduro bike because of the high pressure caused by the low exhaust port height, and heavy flywheels. Try it on your rev and you'll see what I mean.

Fourth or fifth should do it ok once its turning its fine.