Problem starting from 'cold'
 

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.

No its ok, its not like you get 100% correct reading from all meters and the values are in range.

Are you confidant its not the battery?...you should get a fat blue spark 'cracking' across a 2-3mm gap...at least that's what I've always looked for.

After the batteries been on trickle overnight,and is supposedly charged,do you have any idea what the actual voltage is?..it could appear to be holding a decent voltage BUT the cranking power/amps isnt sufficient to turn over a big single.

I had a CCM R30 with a 710 big bore kit on it..original battery struggled till i upgraded to a hyabusa one..same size and more amps.

Thank you for the replies guys. The battery's static charge is now 13.1v, two days after I charged it and after a dozen or so goes at starting it. The voltage at the battery terminals drops to 11.5V when the starter motor is turning. Across the starter motor itself the voltage under starting load is 10.6V. I don't know whether that offers any insight into the battery's cranking power. I think I read somewhere that another way to check the spark is to put a screwdriver into the spark plug cap and hold the shaft near the cylinder head. Is this a good idea? Should I push the start button while I do that?

That plug color chart is useful - thank you - and looking at it my plug might be a little dark which I guess is carbon fouling. So maybe I've got to wrestle that carb out of the bike again. Grrr...

https://www.youtube.com/watch?v=y_P-oAfJz28


Its a normal drop, no point with screwdriver when you have plug inside, i recomend you start following what JJ told you.

I'm embarrassed to say the problem appears to have been a dodgy connection. As I put it back together I noticed some crud right inside the positive plug that connects with the coil. I cleaned that out and the bike started first time. Yeehaa! I won't be stuck in the garage this weekend. Thank you for all your help - it's given me a great troubleshooting guide for any future problems I may have.

Connal..in yer first post...i have the exact same starting procedure...full choke half choke messdin wibthe throttle trying to catch it...engine starting every other second then dying...then when ye thinknthat battery is gonna die...it starts.??. But once started itl start all day long till you leave it overnite

It's sounding more and more like you have something going on with your carb or something that takes way too long cranking to start when it's cold. These bikes should pop off within a couple seconds , even cold . Without touching the throttle , you should use full choke, unless maybe 60-65F, then no choke is really needed. It should crank over easily and in a couple seconds , fire up and idle a bit fast . Depending just how good the jetting is and what the temperature is in 5 to 10 seconds you can shut the choke off and have it idling normal . If it takes more than that and has troubles running once started then there is something wrong . You should never need to touch the throttle on these for starting , that's a big red flag .

Things I'd do to trouble shoot something like this is check engine compression first , just to know it's condition to start with. Then check valve clearances , tight valves cause hard cold starting . After those are clear then look into the carb for issues. Possible choke pickup issues with the hole at bottom of the bowl plugged and no fuel getting into that system so the motor can't get the extra fuel it needs cold.

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