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[Stilton]

Hi All. After a carb clean (gunked up after standing for a few years), low mileage bike ran well for a few miles then started to die at high revs. Limped home at low throttle opening then engine died altogether. Suspected a further carb problem so renewed all jets, gaskets etc in carb and replaced fuel just in case; no joy. Started to check the obvious; fuel getting to plug but no visible spark. Replaced with iridium plug, points renewed and re-gaped, condenser and coil replaced (also replaced battery with a new gel battery while I was about it). Visible spark at points but not at the plug. Very (once in a blue moon) occasionally tries to fire but fails to catch. Any suggestions appreciated for next steps; replace HT lead and/or ....?

Also, does anyone know where I can buy a replacement brass battery lead clip (right angled fitting on the end of the battery lead with a hole in it for the bolt on the battery terminal) as mine snapped when replacing the battery (temporary fix at the moment). Hitchcocks don't seem to sell them.

Cheers.

[Paul M H]

First starters you can buy packs of those crimp on battery terminals in most electrical shops maplins or halfords just make sure you get right size holes for bolt. Now to spark Have you replaced the simple things first like HT Lead & plug cap I see you changed HT coil points & condenser and Plug so if not I would renew HT lead and plug cap.

[jaffa90]

It sounds like the plug cap if it`s a rotten resistor or suppressor in it.

[jaffa90]

Why not buy a A.V.O or multi/meter to check all components before re-placing them.

[Stilton]

Thanks for the suggestions. I've already replaced the plug cap so it's the HT lead next!

[Beezabryan]

The capcitor may well have been changed but, sparking at points & non sparking at plug usually indicate u/s capacitor. Sad thing is I've no idea how to check a capacitor. Anybody know?

[Norm]

Bryan, I got a new condensor from our hosts for a MK1 Interceptor that was a dud, can't remember how I was able to prove it was no good but it didn't take long to prove but a bitch to change

[simon]

You test a capacitor by charging it with a battery and the discharging it through a multimeter. If its a carbon nylon HT lead it will most likely be the culprit. From experience if there is a white deposit on the points the capacitor is the offending party.

[Frank]

You should be able to charge it with the multimeter set on a high resistance scale. An analogue meter is best. The needle will rise and then you can dischage it by reversing the leads. The needle will fall. If there is no charge or a permanent resistance with leads connected bothways it is duff. Best compare it to a known good one. It could still fail when hot so it is not a conclusive test and if you have a good one to compare it with you might as well use that.

[Thack]

Frank, just to correct that slightly if I may. You set your multimeter to its highest resistance range. Then apply the leads to the capacitor, and you should see the needle shoot over to the right and then fall back. Reverse the leads and the needle should again shoot over to the right and fall back (this time it should shoot further). In each case it should fall right back to the left (the infinite resistance reading).