Hitchcocks Forum

Just finished helping a mate with his new toy a 500 electric start bullet of 2003 vintage - only 4000 miles and been in store since 2008.

Long story short - bike has Boyer electronic ignition and iridium plug - had bike running fine after full re-comissoning service and tidying up wiring after new indicators etc....one fault remained which was petrol seepage from the base filter of tap.Previous owner has removed de-compressor so with duff knee can only use electric start.

Went over tonight to sort tap out as he has MOT booked for tomorrow - he had also bought a couple of new NGK 8ES plugs - re-gapped to 20 thou / .5mm as per book replaced and pressed starter which turned and engine emitted a great metallic noise - gingerly tried again making sure clutch fully home bike started but then same noise engine switched off - realised we had been trying to start without using choke so choke closed tried again engine started no noise but not running smooth as previously.

Lots of head scratching - only difference was change of plug .....replaced with original iridium plug ....pressed started and fired instantly no noise and ran smooth - tried this several tines and same each time.....THE QUESTION IS WHY?

The Boyer is the electronic one supplied by Hitchcock's in 2009


Any ideas?

Matt

Well for starters your sprag is on its way out, is this a cast iron or an Electra X if cast iron refit the decomp and get used to kickstarting it, remember there is a reason why it was parked up Po new the sprag was starting to fail

As Norm says. One backfire / kickback now, and there will be a chaincase full of rubble.

You haven't given us the full spark plug number. Is it possible the replacement plug was too long, and hitting the piston?

There is only the B which is the thread 14mm, the E is the reach 19mm and the S stands for Standard 2.6mm electrode. If there is no R it means there is no Resistor. According to my NGK Bible. I`d say the plug is correct, except maybe the heat range could be fiddled with up or down; numbers going down down, the plug is in a hotter range.

Ah yes, I've just checked the NGK numbering system. As Leon and Richard say, the plug must be the right length. I can't understand why the other plug caused that terrible metallic noise, unless the engine was suffering detonation. And quite honestly I don't think that's going to happen with a cold engine - you need some pretty extreme conditions.



Sorry - I can't cast any light on the mystery. Except....



Norm: is it right that a knackered sprag can make such a din? I thought they just slipped, although I don't have the benefit of your experience.

Thack you have no idea the noise a sprag can make, in particular a kickback you step back and expect there to be nothing left in the bottom of the cases except a huge hole and oil everywhere. If the gears break the noise can be grinding/crunching,and locking up, if the bearing locks up it can be a whirring/dragging sound you think of it and a sprag can make it and each time it makes a noise you know it is going to cost you money