Spark problems

[sitaylor2003]

Hi

I have bought an EC250 a week or 2 ago and everything was great until today.

The story is this, it was a well cared for bike owned by someone I know but he wasn't getting the use out of it so he sold it to me.

On Sunday it was the day of the first proper ride out for me, I fuelled her up and off we went. Had a cracking ride for about 3 hours with no problems.

I rode her home and gave aher a good jetwashing down, took the air filter out, cleaned it, soaked it in air filter liquid and left it to dry out.

I came to her today and put the tacky air filter back in and went for a ride into town to dodge the Christmas traffic.

I went about 3-4 miles and then heard a rattle which I thought was the chain, looked down - no problems, went a little further, heard a tinny noise, lost revs and ground to a halt.

I went home and took out the spark plug in case I'd got it wet, when I checked the gap it had welded itself solid, it must have arced or something.

I replaced the plug, kicked her over and hey presto she started, I rode around the block with no problems so I thought it was a duff plug, but no, after a little ride later to just check, I went 2 miles or so and the same thing happened it ground to a halt.

I am not the most mechanically minded of people so wondered if anyone had any suggestions as to what I've done wrong, I called the previous owner and he never had this problem before!

Please help as I don't have a clue!

Thanks

Simon

[MattR]

Three ideas come to mind since it is getting hot enough to "weld" the spark plug electrode.

One idea is that the bike is running very lean (hot). Perhaps the airbox boot or reed valve boot are cracked. I doubt this is the case because if it was this lean than the piston would seize too.

Second idea would be the spark itself. Perhaps the ignition coil (part #2 in attached pic) is bad causing higher current (amps) to pass to the spark plug.

Third idea is a wrong spark plug was installed and the plug is running too hot.

These are just guesses, but it will be interesting to see what others here think.

[sitaylor2003]

Hi

Thanks for the responses, it is an early 2002 EC250 and has not really been used in the last 18 months.

Things have moved on a little today, I took the plugs to a local motorbike dealer and one of his mechanics took a look. He has pointed out that the plug hasn't in fact welded itself it has bent the arm over to the electrode presumably from impact from the piston.

He indicated big end problems but asked me to try a new plug, warm the bike up and to rev the nuts off it to confirm if the big end had gone by killing another plug!!!!

I have done this this afternoon and strangley had no problems. So I took another ride (staying near to home just in case) for a good 30-45 mins. In this time Iwent up and down the gears, used high revs, low revs and everything else to test everything, I had no problems so I am now absolutely baffled!

So at least I now know that the plug isn't arcing, but have no other ideas - anybody have any thoughts???

Thanks

Simon