A Real Head Scratcher?

[Nathanh]

I've been renovating a 83 GS 125 for my girlfriend to learn on and have had real troubles with both a weak spark and a rich mix, after 2 mechanics gave the bike back saying they had no idea, I bit the bullet and installed a brand new carburettor and a coil of a SV (I think). It did the trick and the bike starts of the button first time and runs really well.
The problem is that after is starts it sometimes has difficulty idling and will die, but it only ever does this once, once it has died once the bike runs fine for the rest of the trip, but if you don't let it die by using the throttle at the lights then it will continue to try and die until you let it die that one time.
I know it's not the greates problem to have for an old bike like this, but it is really annoying me as I can see how it logically makes any sense.
Any ideas? Or will I just have to put it down to Gremlins?

[Steve]

What does the spark plug look like right after it dies? That should tell you if it's running rich and loading up. Of course, that does not explain why it only does it once.

There are several possibilities why it would die while idling, but the puzzler is why it only happens once.


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[Nathanh]

Yeah the one time only thing was stumping me.

However it looks like it'll be relegated to the gremlin theory as the problem seems to have resolved itself with no further intervention.

[hampshirehog]

It's got to be fuel related but real odd that it only does it once and is then fine. The only thing I can think of is a dodgy fuel feed to the carb and that once the bike has stopped the float chamber has just enough time to fill up and can then keep itself replenished.

Has your bike got a diaphragm operated automatic fuel tap? Might be worth running it on prime to see if that does anything.

Wally