starts miss at 3000 rpm

If any one can help. I have a 74 norton that starts missing and 3000rpm I have installed a sprax ig. new carbs, rebuilt head, rectifer coils, timing is set perfect. It starts first kick idle great runs great until it hits 3000 rpm and starts to miss and won't rev past 5000 rpm. Anyone have any suggestions.

Could be something as simple as crook plug leads ~


A good test is too start the bike up in complete darkness and bring the revs up ~

Even at idle, bad leads will 'leak' spark ~ it is an impressive sight to see faulty plug leads in the dark ~ LOTS of pretty lights ~ :roll:

Stuart SS said:

Could be something as simple as crook plug leads ~


A good test is too start the bike up in complete darkness and bring the revs up ~

Even at idle, bad leads will 'leak' spark ~ it is an impressive sight to see faulty plug leads in the dark ~ LOTS of pretty lights ~ :roll:

Click to expand...

THanks, I'll give that a try

Click to expand...

Here is another check you can do:
Since you mentioned the timing was set perfect I assume you have a strobe light available.
- Hook up the strobe light and run the engine, if you have an ignition problem starting at 3000 you will see that the strobe light starts missing too.
Test both sides and that should tell you if you have an ignition related problem and on what side it is.

/Per

miss at 3000rpm

You may want to check out the cut - out switch on the handlebar, a notorious culprit,perhaps 3000rpm is just the range for it to begin interrupting the ignition.
Good luck. James.