1VJ running badly
 

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.:censored:

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 :frown:

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 :thumbup1:

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.

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 :)

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.

Questions questions...
 

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? :innocent:)

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:

The head temp sensor came with the Trail Tech Vapor speedo.You remove the washer on your sparkplug and it's basically a copper fitting with a wire coming off it which goes up to the speedo to give a temp reading.
On the XT it doesn't fit down the plug hole very well,so after a few times removing and putting the plug back in,it eventually breaks.
It can prove useful in letting you know just how hot the engine is,normal range (NZ conditions here) is around 180-220 degrees.

As for the coil,it turns out once the shop had opened the L/H casing up,that two pickup coil wires had hit the flywheel and were shorting out.All due to the little tab that holds the wires down in that case had somehow come off.The tab had also done some damage to the stator,great!.

So once I get a new or repaired stator back in the bike,it's going to be sold.It's cost me far too much money over the last year and a half and I can't afford to have much else go wrong....Which I don't think much else can go wrong as I've pretty much replaced every worn out part now.
And don't forget,you can only learn by asking questions. ;)

Hey, don't belittle yourself! No bloke was born knowing this stuff either.

Many things, none of them good.

1. Not enough cooling air (obviously)
2. Fuel mixture too weak (caused by, hey, not enough fuel - blocked filter or jet - or too much air - air leak to inlet, mismatched exhaust)
3. Wrong timing (spark at wrong time causes engine to use energy heating itself up rather than powering the bike)
4. Mechanical drag, e.g. binding brakes, causing engine to work too hard
5. Lack of oil (oil prevents heat building up by lubricating, but also carries heat away from the vital bits). It's why oil level is important - less oil = hotter oil.

I'm sure there are more, but those are the most common reasons for overheating. The paradoxical thing is that more fuel (i.e. an over-rich mixture) makes an engine run cool rather than hot. All those little unused molecules of fuel vapour absorb heat if they don't burn. No. 2 is why so many people get problems with aftermarket exhausts. The exhausts flow the air more freely, drawing more air through the engine and weakening the mixture, and making the bike overheat, especially at high speeds. Rejetting the carbs to allow more fuel to balance the extra air is the solution, but it's too much hassle for some, and they end up with holed pistons after a fast run on a hot day. The thinnest part of the piston, the centre, simply melts.

And don't apologise. Questions are what makes groups like this interesting. I've learned a lot in the short time I have been here.

Thanks guys, for explaining the 'hotter' thing - however - how does that tie in with Yobbo's diagnoses of a faulty coil?

Which one of the several causes for overheating, was caused by the electric fault?

And how?

(As I understand it, the coil is in charge of the spark -- so if its faulty, would it cause scenario no. 3?)

The stator was going bad,which is the diagnosis I got from the shop before they'd pulled the bike apart - just doing voltage testing.It wasn't till they pulled the cover off they found two or the pickup coil wires (the little black box that senses the two magnets on the flywheel) had come in contact with the flywheel and were shorting out.With it doing that it's caused the bike to run very advanced by giving a false signal.

Back to my No. 3 above - wrong ignition timing. If the spark occurs at the wrong time, it can cause overheating. Basically, there is a chunk of energy stored in the fuel/air charge that is drawn into the cylinder. If that energy isn't used in providing motion to the piston, it is wasted as heat. If the spark occurs at the right time, the majority (well, 30% or so, but what the heck) is used in moving the piston and the heat produced is less. Too early or too late, and the kinetic energy produced is less, and the heat energy more, giving a) a lack of power, and b) too much heat to get rid of.

One small point in addition. The ignition is timed so that the spark occurs before TDC. In an ideal world, it would occur at TDC to allow the burning fuel to give maximum thrust to the piston. But the fuel takes a fraction of a second to burn fully after it is ignited, so the spark is timed a couple of degrees before TDC so that the fresh charge is starting to burn as the piston comes over TDC, rather than chasing the descending piston down the bore.