Bit of a back story.
Last sunday was out trail riding,coming home the bike gave a cough and started to feel flat.Pulling up at a set of traffic lights,the idle was sitting around 2500rpm,then dropped back to normal after about 15 seconds.
Bike wouldnt pull properly up top,hesitating and missing.
Also the head temp sensor was showing it peaked at 265 degrees.
It is also warming up too quick,almost like it's running lean.Normally when I get to work,the temp is around 170-180ish,fluctuating between that range.Now it it is over 200 in a short trip.
At first I thought it maybe bad fuel,but it's been too long to be that now.

I have checked for air leaks,nothing.
Pulled the carbs apart,they're fine.
Plug is fine and just to be sure I've changed it anyways,which hasnt helped.

Tonight on the way home,my Trail Tech Vapor speedo was going bezerk,supposedly I'd pulled 13,900rpm,temperature warning lights were flashing.
I unplugged the wire that picks up rpm for the speedo from the coil.This seemed to help with the high idle as it didn't do it in the two test I've done tonight.

The surging,hesitation is still there,plus it back fires between gears and also when changing down coming to a stop....Very big backfires like a cannon going off.

I've been told the check the timing,but a Yamaha shop said don't bother as if thats the problem,the bike wouldn't be running - eg CDI would be dead.

So I'm pretty much pulling my hair out now trying to figure out what the problem is.
Since the rev counter/speedo was going ape shit,could it possibly be the coil then as I've exhausted pretty much everything else.

It definately sounds like an air leak.

Yep does sound like an air leak.
I've pulled the rubbers off and can't find anything wrong with them.

Try spraying a flammable aerosol spray around the manifold while its running. Any change in rpm will indicate where the leak is.

Tried that,didn't work

Strange. Dirt in the carb? Have you removed the filter element just above the float valve? Fuel tap working fine?

I have inline filters,so nothing should get through in the fuel.
I had replaced the needle and seat valve,first thing I did was remove the filter on the new parts before putting it in.
So you can see why this is starting to wind me up now

Yeah i can see... Nt the vacuum line for the fuel tap leaking? Id also look at a partially blocked pilot jet. Very strange electrical problem but i cant see how they would be related?

If I were you I'd contact trailtech and ask them what could cause the computer fault,it might/might not be coil related hopefully they can give you a definitive answer.
I dont see how a coil fault would cause the bike to idle higher,that sounds like an airleak/sticking slide/throttle.
You've took the plug out,is the new one the same colour as the one you've replaced it with,whats it sparking like? I think you'll have to work through the ignition system,plug/plug cap/coil/cdi/pick-up.

Lack of power, overheating, backfiring - it all points to a weak mixture. Try doing a plug chop to confirm this. The most common reason would be an air leak, but you seem to have ruled that out. I can't think of any electrical problem that would cause these symptoms. Sorry I can't be more help.

__________________
2006 XT660R daily ride, 1994 XT600E about to be reborn, Blog: http://goingfastgettingnowhere.blogspot.com/

Well today I think I've found the problem.
The bike has been getting worse since the first post,so today I put the aftermarket CDI back in.
Bike lasted about 5-10 seconds,coughing/spitting etc before it died.
It wouldn't restart.
Usually the rev counter registers maybe 300rpm when you're kicking it over....Nothing.

Got another sparkplug from a box,plugged it into the lead,no spark.
So I think my stator has crapped out,which wouldn't surprise me with the previous problems of hard starting/not starting at all when the bike was hot.

Hi Yob

I know this sounds a bit left field but. Disconnect the side stand switch and short it out ( join the two wires together, or bridge it). Then take the bike for a spin. I had simillar probs with my 3aj - after much wasted time and money, this is what it was, an intermittent fault with the side stand switch.

I'm now convinced that the root of all evil in the world - is the xt600 sidestand switch

__________________
Remember what Yoda said\", there is no try, either do or not do\".

Good thought Dave O,but this model has never had a sidestand cutoff.
Since it's NZ new and with a 1VL(no idea why they've coded them different) frame code,the only starting inhibitor it's ever had is a clutch cutout,which isn't there anymore.

Just another small update for those interested.
It's turned out the charge coil is breaking down and giving inconsistant reading.
So that makes things nice and easy now.

Hey. You're probably going to regret that I am very interested, because I have a lot of questions.

I'm a girl, so they will probably seem like very stupid questions to you - but hey - I've got to learn somehow!

I'm sure all you blokes know the answers, so please help.

[btw I have a 1vj too and have been doing some real rocket science stuff, like swap engines (whooo-hoo) and cut lovely gasket shapes from card (fun!) and replacing stators (boring) etc.]

Question 1:
Why do you have a head temperature sensor? Is it the same as an oil temperature sensor? Do I need one? (Or do I perhaps have one, but its in a secret location, that only blokes get told about? )

Question 2:
Why would a faulty coil cause the bike to run hotter?

What makes an engine "run hotter"? I thought it was something logical, like not enough cool stuff (air). Ooorr... too much hot stuff (fuel?). Or too much friction or something?:confused1:

__________________