Poor starting when not started for over a week.
 

My XT600E 4PT starts first push of the button from cold, if it has been started within the past few days. But leave it a week or more, and it's touch and go whether the bike will fire first, or whether the battery will run out of juice first, and getting it started often requires jump leads and more than 30 seconds on the starter button.

Any ideas what could be causing it, and if anything can be done to fix it?

So far I have put it down to fuel evaporation and/or degradation within the carb bowls, and the bike can't start until fresh fuel has been pulled through, but this is a guess.

The most likely cause is a sub optimal battery. The motor etc will likely be tighter etc if it's stood for a while (including fuel evaportaion etc and all the other elements.) The load placed on the battery (remember they are not deep cycle batteries) will cause a voltage drop when starting. If you can measure this and see with a multimeter the voltage must not drop below 10v when cranking the starter motor over. Also note, running at a lower voltage can cause the starter motor to draw more amps to compensate (this becomes a vicious circle leading to weak spark etc as a by-symptom). This can severely shorten the starter motor life.

He said it still takes 30secs with jump leads....

You need to fix/check all the obvious things, even if its just to rule them out:

Fresh sparkplug (and verify good strong spark)
Clean carb and jets
Fresh (or cleaned) airfilter
Check/adjust valves
Check battery voltage, while idling, reving, and under load (turn lights on without starting the bike voltage should still be over 12v)

Then you can do some real troubleshooting.


As a temporary fix, try to turn the fuel of a couple 100 meters before you get home. See if it helps.

Good luck.

Absolutely. This does not detract from a low battery scenario. It adds to it. Notwithstanding any engine that has stood for a long time is generally harder to start.


The above would not necessarily be symptomatic of a hard start after a lengthy period of being parked up, but would if it's a problem of hard starting from cold which is not the case. Also I dont believe cleaning the carbs will solve the issue even if it is a maintenance task as all of the above points are. However, potential airlocks in the fuel hose and sticky float valves may well be symptomatic. I'm still sticking with the battery as a first port of call. It's also the easiest to check tbh.

Sulking after being left.
 

My 3AJ Tenere is similar. If I drain some fuel through the bottom of the carb first it starts fine, but the drain screw is starting to round off.

Thanks folks, keep the suggestions coming.

I don't think the battery is suspect, it will turn the engine over for 30 seconds or more and sounds like a good strong turn of the starter, but sometimes that's not enough for the bike to fire, and then I have to get the jump leads out. I will test it though because as you say it's easy to rule out.

I could understand low voltage effecting spark on a bike where the battery feeds the coils, but is the XT not a CDI magneto type system anyway, ie: it doesn't actually need a battery to start? One of my engine covers has a blank plate where a kickstart obviously used to be on older models.

Fresh sparkplug (and verify good strong spark) - Done
Clean carb and jets - Never had them out, but have run Redex through
Fresh (or cleaned) airfilter - Done
Check/adjust valves - No, I've never checked them. What's the service interval for them?

Will also try the fuel draining trick, if that works then it's definitely a fuel evaporation/degradation issue. Like I said, if it's been started in the last 3 or 4 days it fires first time, which tells me it's something related to the amount of time it's been standing.

Jens suggestion was good, good practice in any motor in fact. Turn off the gas taps & let the carbs run dry, and splash out on a new plug.

Mezo.

+1 for running off some fuel when coming to a halt for any length of time. It's not needed for stopping for a cup of tea, but I have developed my own procedure to shut off the fuel tap before stopping the engine at the end of a run. I have found that this helps for cold starting after the bike has been standing for a while. Trying to explain this to myself but I don't know why it should help - one guess is that the float might stick in the up position so starving the engine of fuel until it drops. Who knows?
Also, I don't necessarily run the engine completely dry - I usually just run off some amount of fuel so that the float is not at its' highest position while standing for long periods.

Hope this helps

Another vote for the fuel draining fix. My XR600 is exactly the same - leave it for a week and it can take hours to get it going (kickstart only). Drain about half a float chambers worth of fuel out first and it's first or second kick.

hi guys if my 1985 43f xt600 is left for more than a week i drain the carbs , it starts up strieght away if i dont drain the carbs it can be a 20-25 kick job. modern fuel must go off in small amounts ie the carb bowl ? . zigzag

Flush out your fuel tank
 

I had a similar problem on my 3AJ. What seemed to resolve it was taking out the fuel tank and flushing it out.

If I left the bike for any length of time it seemes that water rather than fuel settled at the bottom of it, so that was being drawn through the carbs and the bike wouldn't start.

Euan

Interesting theory about the water in the fuel tank. The bike has been run out of fuel completely recently though (that's not part of the problem, it was like it before), would that not have left the bottom to the tank dry?

I don't have an answer but your not alone, my 3YF 660xtz has been the same since I bougth it 4 years ago, leave it a day and starts on the button, two days and it takes 10 seconds, 3 days and 20 seconds and a week its 30 seconds, after about one or two months it takes over a minute, thankfully the previous owner put a new battery on before I bought it and it turns over forever:-)

I guessed it has something to do with the vacuum fuel pump needing priming , but I might try the turning off the supply before stoping and see if that helps

I just need to use it more :-)

Shut off the fuel tap
 

Hmmmm, seems that the theory and practice is good even if no one has a full explanation. It has certainly been my practice for any single cyl bike that I have ever owned that has a fuel tap - so that will be any single with a carb. Funnily enough I haven't tended to find it necessary for the inline 4s' that I have owned.
And I still don't know why it helps :innocent:

Well thanks folks. About three weeks since the bike was started, drained some fuel from the bowl, opened the tap, and it fired second turn of the starter. When it came to put the bike away I just let it tick over on the driveway with the fuel tap closed. By the time I'd got my helmet and gear off and put away, the bike had run out of fuel and cut out.

Hopefully it'll fire first time the next outing.

Still not an explanation of what the problem is but at least it's a work around.