I've got a 1997 XT600 E which has been fine starting in the morning through the summer but has recently become very reluctant to get up and going. I live in Portugal so it's not like a cold northern European morning. I've tried everything the good people on other forum posts have suggested - full choke no throttle, a few twists of the throttle first, half choke etc but what happens is this: the starter motor turns fine (after battery being on trickle charge all night), nothing fires for the first few goes and then I get a single fire which dies immediately. I persevere and fiddle with throttle/choke combinations, get ten or so more short fires and finally, just before the battery has no more to give, it starts. I'm concerned about the damage this will be doing to the battery but don't know where to start looking for the problem. Could it be the choke not working? Is it something to do with the carb float (which sticks intermittently and dumps petrol on the garage floor when I stupidly forget to turn off the petrol tap)? I've recently stripped and cleaned the carbs and changed the air filter but it started fine for a few weeks after that so I don't think I messed anything up in the carb. I'd be grateful for any advice on where to start looking.

Well,,,,, First would be fixing the reason gas is pouring out if you leave the petcock on. I don't remember if the XT carbs will dump the gas on the floor before it gets into the motor or air filter. You have either a bunch of junk jamming the needle valve or the valve itself is shot. Also, If your float is set too high(or not installed right after cleaning?) it'll also keeping flowing and not shut off , flooding the motor.

There really is so many things that can be going on but without being there it'll be a long drawn out thing.Some things that should be known to help,

1)Is the starter spinning it over fast enough , as in battery good, starter working fine ect..
2)Is it getting too much gas or not enough ? after trying to start is the plug wet or dry ?
3) are the valve clearances right ?
4) is the carb really clean , I know you cleaned it , but that's seldom done completely and often it takes way more than a person thinks to get all the little passageways clean , takes experience with carbs to know for sure.
5) is there good spark ? is the sparkplug new or in good condition.

That's just a start with the info given.

Why are you having to put the battery on trickle charge overnight?..is it failing?.id be inclined to change the battery...

Thank you for the advice. I've done as you suggested jjrider and taken the carb out to check the float and valve. As I was doing this I noticed a small amount of petrol seems to have blown back into the air box from the crankcase. Could this be relevant? The float height seems ok and there was no obvious gunk in the valve but I will give it all another good clean and blast some air through the jets anyway. Nikroc the battery seems ok - charging voltage and voltage under load all seem to be as they should be. Once the bike gets going in the morning it starts with no problem all day long. I just trickle charge it every few days because of the number of goes it is taking to start it. My normal weekday rides are not long enough to fully charge the battery.

It's sounding like it isn't getting enough gas for the colder temps in the morning. Whether that's is due to a partially plugged pilot jet , choke not working or simply not jetted rich enough I don't know. One thing I'd do it turn the mixture screw out 1 full turn and see if it changes for the better. Also what is the pilot jet right now ?

As far as I know (I've only had the bike since the summer) the pilot jet is the original stock Yamaha one. I've discovered I had a leaking petcock which I guess might explain the petrol on the floor. That seems fixed now and the carb is back on the bike with the mixture screw out one more turn but there is no improvement. Which leaves me thinking I need to follow your other suggestion of checking the starter motor and spark plug (which is new but you never know). I've researched how to check for voltage drop in the circuit leading to the motor but do you have any advice on how I go about testing the starter motor itself?

Sorry to keep banging on about this but I think I have got a step closer to diagnosing the problem. I could just do with some help in interpreting the numbers. I checked the spark by holding it against the cylinder head and it seemed weak and sporadic (also mostly yellow with just a hint of blue at the edges). The spark plug is new and held out fine on a resistance test so I figured the problem was somewhere else in the ignition circuit and followed the manual instructions for checking this. Two things showed up as being out of spec but I don't know if either are significant enough to make a difference. Resistance across the spark plug cap was 11.48k ohms instead of the specified 10k, and the primary ignition coil showed resistance of 4.9 ohms which is a little outside of the 3.4 to 4.6 ohms specified in the manual. Could these discrepancies be enough to make a difference? I just can't get my head around how these could make the bike so hard to start in the mornings but still allow it to run just fine for the rest of the day. Thank you in advice for any advice you can offer.