Bike not firing up

[masterofinsanity]

Had a few problems recently with the bike not firing up when you hit the starter button, it just spins the engine over and over, at first i put it down to a dodgy ignition switch as if i turned it off and back on again it would fire up.Then after ripping the junction box apart noticing there is a relay in there i thought it might be down to this but after reading millameters thread i'm thinking this relay just determines if the starter motor spins or not?? Anyways its getting worse to the point i'm not risking taking it out now as Jamz noticed last night it just didn't wanna fire and this morning was the same.

Any suggestions?

[Tyrant]

Here's the circuit I posted in another thread;



The relay within the junction box determines whether the starter motor spins and the fuel pump gives a little juice as far as I can tell. So if it is spinning and sucking some petrol you could elimainate that?

[zimm]

is it "not sparking" or "not firing" ? does it do it when hot or from cold ?

does it spin over quickly ?


cos,

if it spins over quickly, mainly only fails to fire up when hot.. it could be a combination of slightly rich idle mix, and low compression due to tight valve clearances

[masterofinsanity]

i swapped the coils last week and all plugs are sparking, and its doing it any time hot or cold.i wouldn't say it spins any faster than normal.will try and look at it tonight maybe check the battery voltages etc.

[masterofinsanity]

could it be anything to do with the resistor in the ignition switch?

[zimm]

sounds like the issue cargo had with his racebike, which turned out to be the wire to the ignition pickup IIRC, check the yellow one hasnt gone all brittle and brown coloured.

if the ignition switch resistor is gone, you get no spark at all.

[masterofinsanity]

rightyo, thats the one under the ignition pickup cover aint it?

viewtopic.php?f=7&t=6567&p=51839#p51839 cheers zimm.

Long story cut short............last year..........
I built a ZXR400 specially for the Manx........from the day I finished it there were were starting problems....it sometimes took ages to fire up and usually killed the battery trying..............once it did start and got warmed up it was even harder ti get it going again.

While riding it there was a vert strange intermittent misfire not quite off a cylinder or two but nearly.............

Anyway I couldn't figure it out.............I had to ride a very much slower bike in the races

Once I'd got home I checked every bit of wiring in minute detail....and found that the little bit of wire from the pick up coil that is inside the engine csing had got very hard and brittle and was discoloured slightly................... also the was a crack in the insulation.
I replaced the pickup coil and the wire complete and hey presto all was fine ..............same bike is still going really well now.

would also explain the bike sounding like a triumph as well.??