Having problem with my ds 650 when in fifth gear at top speed my bike will drop about a 1000 rpm all the sudden and if I dont let off the gas it will die. could the problem be the cdi boxs? I have Big Gun rev box on it.

 

It sounds like a fuel problem. Check vents ,fuel peck (flow to carb bowl) and needle and seat in the carb, In that order.

 

mine did that, when the float level was too low

 

If you have a tach, note if you are hitting the rev limiter - 8700-8900rpm

 

In gears 1-4 my tach will go up to 8300 but in fifth gear it goes up to about 6500 and the it will drop.

 

When you pulled a plug, what was its color.
If wet and dark, pull out the other plug also.
One step at a time.

OMR

 

I have a inline fuel fillter on it could that be the problem

 

Bingo.
I would disconnect the filter and retests.
I tried a inline filter once and it went dry for me also.
I think the DS is too large a motor for these small filters.
Check one plug also.
OMR

 

Ok i will try it without the fuel filter on it. could the problem be the cdi box??

 

I have had cdi go bad, but not intermittant.
Cdi's either work or fail.
On cars the coils will sometimes fail at a high rpm under load.