So, tank came off today - it looks as though there is no damage to the cabling for the FI. I've added padding to the potential wear areas.
I tried to look at the connection for the regulator rectifier, but struggled to get it off.
Washed the bike with a pressure washer (always do) Bike started no problem.

Battery was still good after 36 hours.

So back to square 1 - not sure if it's cold or wet that causes problems....

So, It's been warmer and drier since I last posted...

It's mostly been starting without problems.

I've been under the tank twice, noticed some exposed wiring 2nd time round - not the two cables that clip into the tank, but the clip that sits in front of the snorkel. It has a red/blue and red/black cable, the red/black had missing insulation. Covered it with self fusing tape, put the bike back together. I thought I sorted it.

Starting was interesting - revs increased in slow motion and eventually it started.

Heavy rain on commute to work and the stuttering kicked in at 70 mph / 4500rpm. Eventually it stalled and would only restart after a rest and 5/6 attempts. Then continued without problems and started fine.

I'm all out of ideas. :-(

Has anyone got recommendations for an electrical specialist in Herts or London?

Thanks again,

Chris

How much attention have you directed at testing the coil and HT lead? Breakdown of the HT side of the ignition can be attributed to dampness and to temperature. It can also cause bad starting, stuttering and miss-firing, all of which can quite often be intermittent. Worth a further look?

How about the spark plug? Have you tried a different one? There are a lot of fake NGKs about on ebay, especially iridium types which cause bizarre and random symptoms.

Get one of those squirty bottles filled with water and with the bike idling good give the HT side a soaking.

Be careful and do a small bit at a time plug, ht cap, cap/ht cable joint etc etc. give each bit a soaking wait a bit and check bike is still running ok

Traced a breakdown in the insulation of the coil HT lead joint on my TTR like this would have never seen it otherwise.

Run it in the garage at night with the lights out. Have a good look around the HT side of things.
Any arcing is easy to spot, do the water spraying over things as well. Good luck.

Hadn't spent any time testing I'm afraid - bike maintenance is still pretty new to me. Only had it just under a year - so baby steps.

Wouldn't start again this morning - today I had thick fog!

I think I'm getting somewhere!

Sprayed various connections that had been mentioned throughout the post whilst the engine was running.

The engine stalled almost immediately when I wet the coil. Wouldn't start again - got out the blow drier - started fine. Sprayed coil and stalled again. Dried and started fine. Went for a spin - no probs. Sprayed coils with a hot engine for around 30 secs and couldn't stall the engine, no stuttering or otherwise. Had to stop there as it was dark outside and I do like my neighbours.

I need to do more spray testing - it does seem to be the coil end of things, how precisely should I be aiming or does the whole coil count as a unit and aiming widely at it is all I need.

If it is the coil, is this something I can repair, or should I replace it. Could I swap this myself. I haven't yet found a coil to buy, are they only available via dealers? How much money am I looking at?

Sorry for all the questions, I'm over the moon I finally replicated the issue and am eager to sort this out.

Thanks again everyone!

The coil is a sealed unit and is not serviceable. However, the HT lead and the plug cap can be replaced separately with non-Yamaha items fairly cheaply. So it might be worth seeing if you can isolate whether it's the coil pack, HT lead or cap. Most of the trouble seems to come from the coil to HT lead joint, so focus on that area if you can.

Yamaha want about �85 for a new coil (with HT lead pre-fitted) and a further �40 for the plug cap! As any decent silicone HT lead cut to length will work, along with an NGK or other decent plug cap are not expensive, it is probably worth changing them out first?

You can get Nology high performance coils and HT leads, but they work out only fractionally cheaper the Yamaha, although the are probably better?

Don't forget as well that spraying the whole area with water mist will also show up a plug with a faulty ceramic insulator, as any leakage will trace through to earth with the damp. On a hot engine the plug's insulator will be less likely to leak to earth in the wet as it will by very hot and the water will evaporate almost instantaneously. This could be a reason why you could make it stall cold, but not hot? Try a new plug.

http://i374.photobucket.com/albums/o...kmoto/Coil.jpg

Go from 1 to 4 my moneys on 3

+1 That's the point where I have had a problem in the past.

Riding in snow and slush, the water was coming off the radiator and getting that joint wet. Try starting the engine and touching that joint when wet, I guarantee a bit of a jolt!:icon_eek:

Hmm, I've tried a few times to replicate the fault without success. Only managed twice last Monday.

Not even with a cold engine, could I get it to stall. Tried focussed water sprays at no. 3 as well as drenching everything around the coil and spark plug.

Could it be that the ambient temperature needs to be low as well as the wet?