Random idle misfire after rebuild

I did a total engine rebuild. New rings, cylinders honed , valves job , new oil seals everywhere, new camchain, head lapped, new gaskets. Good compression, carb rebuild too. New nos intake boots.
Engine is running perfect with new foam pods.
Mid range perfect.
Wot operation perfect, acceleration is good, she can easily reach 70 mph flying through the gears
Cold and hot starting are normal.
The bike idle well, 1100/1200 rpm.
BUT WHEN IS HOT after a 3 or 4 miles she start to misfire ,only when idling , for just a second.
It is Like a ... "Brrrrrrrr-TUMP-brrrrrr-TUMP...." LIKE 1 or 2 cylinder loss power for just a second.
I tested my ignition coils with a hairdryier and i have always 3ohm primary and 12.90 ohm secondari.. In both coils.
I swapped the IC igniter no luck.
I saw i have a broken magnet in the pulser coil. It is possibile this kind of issue due to this magnet?
Any help will be very apprecciated.

I forget to mention carbs are synched and i have new spark plug cap 5kohm , new no-resistor HT leads, and new ngk D8ea...

You also forgot to mention what kind of motorcycle you are talking about. PLEASE add the bike's year and exact model to your signature line. That way you don't need to remember to put that info in the text of every posting. Ed

Uhuh, your right ed. I talk about a 1983 KZ 550 H
Gpz unitrack. The one in my avatar.
I had this issue even before engine and carb rebuild.
I was thinking about dyna but honestly it is really too expansive....
Im searching for a good used pulser coil, IF this can be the cause of my issue.. I'm really Not sure about

Mine has done this as well. Have never been able to figure it out.

The_Proletariat wrote: Mine has done this as well. Have never been able to figure it out.

You tryed with new ignition components?

shamal wrote:

The_Proletariat wrote: Mine has done this as well. Have never been able to figure it out.

You tryed with new ignition components?

Yes. Dyna S and 3 ohm coils. I've never had a good idle under 1400 or 1500 rpm.

Been through carbs, ign, and valve clearances and could not figure it out so I gave up. I will be watching this thread to see if there is any resolution.

I have a steady 1100 or 1200 idle.. This is the strangest thing. I have a perfect engine that when warmed up properly start to miss one or more spark, or at least i think about spark..

I cant figure out this thing. I think i can say it is Not mechanical. Engine is quiete, all new componenti except ignition system.
I really dont inderstand the function of the magnets in the pickup coil and if that cracked magnet can be the cause.
If you had the same issue even with dyna .....i think im lost.

shamal wrote: The bike idle well, 1100/1200 rpm.
BUT WHEN IS HOT after a 3 or 4 miles she start to misfire ,only when idling , for just a second.
It is Like a ... "Brrrrrrrr-TUMP-brrrrrr-TUMP...." LIKE 1 or 2 cylinder loss power for just a second.
I tested my ignition coils with a hairdryier and i have always 3ohm primary and 12.90 ohm secondari.. In both coils.
I swapped the IC igniter no luck.
I saw i have a broken magnet in the pulser coil. It is possibile this kind of issue due to this magnet?
Any help will be very apprecciated.

Hot misfire is usually a coil. bench tests can never find flaky coils.

Valve clearance on target?

You may want to try this...

When the engine is still cold and running with no misfires use a hair dryer or other tool to warm up one of the coils. If the engine then misfires, that coil is suspect. If not, heat up the other coil to see if that causes the misfire. Ed

650ed wrote: You may want to try this...

When the engine is still cold and running with no misfires use a hair dryer or other tool to warm up one of the coils. If the engine then misfires, that coil is suspect. If not, heat up the other coil to see if that causes the misfire. Ed

Ed, he said he did that in his 1st. post,
Pete

DOH! :blush: Ed