Cold Starting Problems.... please help

AndyBantam · L Plate Warrior Joined: 24 Apr 2006 Karma :

Hello all, I am new to this site and I was wondering if you could help me with a problem that has had me pulling my hair out for some time now?...

I have recently purchased a Siamoto Favourite125 scooter and it absolutely fails to start when cold (unless you turn it over for ages to get some heat into the engine). When it runs, it's fine - no problems at all. It's just wont start when cold.

Any help offered would be greatly appreciated.

Andy

P.S. Apparently, the engine is a copy of a Honda unit - if this helps...

JGY6000 · Trackday Trickster Joined: 25 Sep 2005 Karma :

have you tried using the choke??

WavyGravy · Scooby Slapper Joined: 10 Mar 2006 Karma :

Welcome to the site.

you havent really given a lot to go on, has the bike always been difficult to start when cold - or is it getting worse? - is it 4 stroke or 2 stroke?

Try cleaning the plug/resetting plug gap

try a new plug

Clean air filter, does bike have an automatic choke? is it working?

is ignition timing correct?

Genuine Honda 125 four strokes generally start easilly, the chinese copys are of variable quality from what ive heard, anyway enough there to keep you busy for an hour or so!
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1975 CB125s, 1991 GN250, 1990 Ducati Paso 906
"Don't wake him up - He's got insomnia - He's trying to sleep it off"

shammon · World Chat Champion Joined: 24 Jun 2005 Karma :

Check the battery!
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YAMAHA YZF 1000cc THUNDERACE- 'ƃuıןןǝds ʇnoqɐ ʇıɥs ɐ ǝʌıƃ ʇuop ı

AndyBantam · L Plate Warrior Joined: 24 Apr 2006 Karma :

The bike does have an automatic choke. Being technically minded, I tested the feed to the automatic choke but there was no voltage. At least I think it's an automatic choke. When it's removed from the engine, it looks like a box with a needle sticking out of it. The needle looks like it should retract into its housing.

Here's the interesting bit...

I tested the feed connector for insulation resistance by measuring the resistance between the two conductors; it appears there is a short, as there was no resistance. I traced the wires to the front of the bike where one wire connects to what looks like some kind of heat sink. It's mounted right at the front of the bike, just below the instrument panel. (Any ideas what this part could be?) The other wire connects to some kind if sealed metal box (looks like some kind of heavy duty resistor). I found nothing to make me believe that the wiring loom has been damaged or no signs of a short. I need to know what should be happening at this connector.

The bike is brand new but has no warranty as it's second hand and has been sat under a sheet in the previous owner's garden for a while.

The battery is fully charged, the engine runs fine when it finally starts. When warm, it will start every time. It's a four stroke 125 - apparently a honda clone engine.

I know nothing of bikes and what goes on when they start and warm up, so I need just a few pointers and I'm sure I'll be able to sort it out.

Thanks folks.........

meooo · Nova Slayer Joined: 23 Dec 2005 Karma :

Auto chokes usually work through a bi-metallick spring (two different metals sealed together, one reacts quicker to heat than the other) it can be heated by water or an electrical feed (the power causes heat, or the coolant warms up, the spring unfolds, takes off choke)....easy peasy!

Usually the electrcal feed will come from the alternator to the choke unit.........if the engine doesnt run and start charging, the choke wont come off/take power from the battery.........This usually means the choke will stay on though. Could the "heat sink/sealed relay" be the rectifier for the charging system on your bike?
If there is a feed to the choke unit with the engine running I suspect the spring assembly is duff/not properly connected to the carb and so not putting the choke on when cold.

AndyBantam · L Plate Warrior Joined: 24 Apr 2006 Karma :

Is it worth telling you that the needle on the choke is out the way out when removed from the engine? Should this not be the case?

Yoshi · Traffic Copper Joined: 05 Jul 2005 Karma :

The goblins who run on wheels inside the engine to make it go are just like you and me, they don't like being woken up to run around when it's cold. Have a bit of consideration, at least bring them a coffee or something! Jesus, some people have no sense. Rolling Eyes

You can't just expect them to jump up when you come along.
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Present: GS650 Katana - Getting ready for summer touring!
Past: TS50, RS50, ZXR400, LT80, TS250

WavyGravy · Scooby Slapper Joined: 10 Mar 2006 Karma :

The large resistor at the front of the bike is probably switched into circuit on dipped headlights, it stops the bulb being blown by dissipating some of the current as heat, it gets switched out again on full beam.

sounds like you're on the right path with choke, isolate problem by covering air intake on airbox and starting engine, make sure the rubber manifold between airbox and carb is not leaking as well, if engine starts youve found the problem. Just a guess as I know a bit about hondas but you still havent told us what bike you have!

If any gremlins escape, keep them away from water
____________________
1975 CB125s, 1991 GN250, 1990 Ducati Paso 906
"Don't wake him up - He's got insomnia - He's trying to sleep it off"

AndyBantam · L Plate Warrior Joined: 24 Apr 2006 Karma :

I did tell you what bike I have....

WavyGravy · Scooby Slapper Joined: 10 Mar 2006 Karma :

sorry, my mistake, thats the trouble with trying to read forum over an early breakfast

Have no knowledge specific to your bike
____________________
1975 CB125s, 1991 GN250, 1990 Ducati Paso 906
"Don't wake him up - He's got insomnia - He's trying to sleep it off"