My '82 seca 650 starts fine, charges fine, and runs like a champ for the first 4 miles or so, then starts to stutter / stammer / fall down and then seems like it's running on 2 cylinders. After it comes out of it's hesitation mode, it seems to run fine. Can anyone troubleshoot this problem for me?

Is it the coils, maybe?

Any help is appreciated....

The coils provide high voltage so that the plugs can ignite the fuel/air mixture coming into the cylinder.

If you have 4 working cylinders before the bike warms up, and only 2 when it's warm, it would rather indicate wrong fuel/air mixture on these cylinders. It helps to clean the carbs and tune them when the engine is warm. that way, you're synching to the state the bike will be in ideal operating temperature.

The coils provide high voltage so that the plugs can ignite the fuel/air mixture coming into the cylinder.

If you have 4 working cylinders before the bike warms up, and only 2 when it's warm, it would rather indicate wrong fuel/air mixture on these cylinders. It helps to clean the carbs and tune them when the engine is warm. that way, you're synching to the state the bike will be in ideal operating temperature.

Can anyone send me a link to how to sync my carbs?

Thanks.

Well... it's not an exact science. If you want them to be fixed without worry, go to a mechenic.

You're gonna need some tools. It may well be that the investment you're going to make is more than it would cost for a mechanic with these tools in hand to do.

If you're still inclined to do it yourself (as it should be), read on..

Information passed on from the xjbikes.com forum

Tools needed:

Screwdrivers, small flathead for the idle mixture screw and phillips for the butterfly valves

Various pliers

Wrenches and sockets (the YICS passage is blocked off on either end of the engine block by a 12 or 13 mm bolt)

YICS tool to block off the YICS passages (if your bike has this, the covers of the crankcase reads "YICS")

Colortune plug for tuning the idle mixture

4 channel manometer for tuning the butterfly valves (you can get away with a 2 channel, but I prefer to see all the ports at once)

The proper way to do it is thus (while the engine is running):

Warm up the engine for a good 10-15 min.

Colortune cylinder 1

Sync the engine with manometer

Colortune cylinder 2

Sync the engine with manometer

Colortune cylinder 3

Sync the engine with manometer

Colortune cylinder 4

Sync the engine with manometer

The lazyman's method is to first colortune all cylinders, and then do a sync. You might want to get a longer fuel line than the existing one. The tank has to come off, but it still needs to be connected to the carbs.