Hi guys!
Last saturday I was riding my (1986) Tenere in France and everything was working fine but after a stop the engine refused to re start and even pushing the bike the only result was to have the engine starting (coughing) but not taking any throttle. Found a mech who diagnosed generator breakdown saying the spark at the spark plug was very weak.
Any idea? and if the diagnosys is good where to find an used generator as a new one costs 550€ (!!!)
thanks
giboun

Hi What about checking all the rest plug, spark plug, ignition coil, battery not connected propery etc...before going for the generator.
Good luck

Maybe the weak spark is just a coincidence and the weak fuel-pump is the culprit . Just a thought .

at least put a new plug in before anything else...

Throwing a lot of money to a probaly easy problem.

If ther is a spark, although weak, engine should start. You have a spark, so suspecting the ignition is not obvious. Before dishing out a large amount of whatever currency first check the obvious things, and make sure it is indeed the alternator. There's alos a CDI, and the coil, and the wiring ...

Fuel: are you sure enough fuel is arriving in the carb? Unscrew the drain plug, if loads are coming out (taps open :-)), you are ok. If, not find the cause.
Carb float stuck makinh mix too rich?

Check / replace spark plug, how does it look?

Etc

Auke

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Auke
http://aukemarieke.blogspot.com

Lots of good advises!! Thanks a lot.
As soon as I will be able to get back the bike (I had to leave it in France!!) I will surely proceed to analyse thinghs according to your info
Let you know
cheers

giboun

If you can charge the battery up using the mains, then hook up a multimeter to the positive terminal of the battery and a good earth spot on the bike (somewhere on the frame), start the bike with all extras like lights off, the voltage should be about 12v. Switch on all the lights, indicators, full beam on headlight etc. on and the voltage should stay up at around 12v. If it starts dropping then it's some problem with your charging system. If I recall correctly throttling up should increase the voltage momentarily before it settles again. Try topping up your battery (unless its maintenance free of course!) and checking the alternator is properly earthed etc. before assuming it's something really bad.
If the bike doesn't start with a fully charged battery then it ain't your charging system.
Matt

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http://scotlandnepal.blogspot.com/

*Disclaimer* - I am not saying my bike is better than your bike. I am not saying my way is better than your way. I am not mocking your religion/politics/other belief system. When reading my post imagine me sitting behind a frothing pint of ale, smiling and offering you a bag of peanuts. This is the sentiment in which my post is made. Please accept it as such!

Hi giboun,

I hate to say this, but don't be too quick to dismiss the altornator windingd theory.

My 3AJ Tenere became more and more difficult to start until it would only start on a brand new spark plug, even if the old one had only done 10 miles. The spark looked good with the spark plug rested on the side of the head, but it has a much harder time under compression.

A multimeter resistance reading of the coil that lives amongst the alternotor windings that supplies power to the CDI was about 10% lower than expected.
It took me some time to believe that this could be the problem, but eventually I replaced the alternator / CDI windings and it then ran perfectly for about 30 000 miles.

When I removed the windings I discovered that they were not original Yamaha ones but aftermarket ones that were supposed to suit a number of different bikes.

If I was you I would get a decent DMM that can measure in 0.1 ohm steps, unplug the CDI coils from the wiring loom and check their resistances against what Yamaha quote. I would also measure between them and 0V / frame - there should be extremely high resistance. If all is correct I would not consider replacing them.

also suggest getting the thing that you can fit between a spark plug and it's cap, that flashes when it sparks. This way you can check the plug under compression. They are very cheap anmd available from car accessory shopr.

Hope this helps.

If you need the resistance figures, let me know and I will find them out.

Mark

Hi Matt,
Thanks a lot but I am now one step behind as I actually cannot really start up the engine, therefore I cannot check anything with the engine running...
Re Matt reply it would be great if you can give me the resistance values to check.
I am seeking for a factory repair manual for the bike and, as suggested on this forum, I contacted [mega.bikes@gmail.com] who replied the manual is available but then he did not come back to me about how to give him my offer to get it downloaded.
Any other suggestion on how to get a manual?

thanks
giboun

hi guys; I´looking for users manual for XT600z 1 VJ model (kick & electrical starter). I need complete electrical scheme. I wonder, if anybody could help me. I was searching the whole forum, but i did´n find anything.

thank you, Mike.

I know that the tt and xt 600's here in the states had issues with the cdi up to 89. The symptoms are very similar to what you are describing. Yamaha had a set of resistance specs that they put out to verify that the cdi was good or not. Mine had those issues and I replaced it with an aftermarket cdi from wayne.gum on ebay.