My wife has a 2000 ds650 which had a stock cdi box when we got it. She seemed to be hitting the rev limit to easily to me. I replaced the stock cdi with a Ron Woods. This seemed to increase rev limit a liitle but it still starts cutting out in higher revs and actually stalls out! I took it to a recomded dealer who serviced the carb but were unable to find any other problem.
When I let them know same problem still exists they checked with their racing dept who thouht it might be a defective cdi so they swapped me out a new one. We tried it out but still having same issue. According to the shop manuel, I think it might be the coils. Anyone have any ideas on what this could be???

 

Could be the coils some time the mounting bolt will work lose, or it could be the gas tank vent tube is pinched or the rubber boot in the carb is torn.

 

What kind of pipe you running,check your jetting,there's a vent tube wrapped uner your tank, had one pinch one summer, had your symptoms, bigger back tires will put your power in a lower rpm range and on the ground, hope it helped!

 

The petcock on the fuel tank also has a screen that could be clogged, try switching to reserve and see if it helps..

 

my yellow bike was doin it and the diaphram in the carb was torn

 

i bought mine used and it was doing that. the jetting was way way to fat!

 

The first thing to check, which is the easiest is to loosen the gas cap enough so that air can enter the gas tank from the cap. If things clear up, then it is likely the small plastic tube that winds around the gas tank. (As previously mentioned.) If loosening the gas cap solves the problem then re-route the small plastic tube making sure it is not pinched & re-check. On a stock engine, you shouldn't have to go any further than that.

If that doesn't help the problem then I would look at the other items people suggested - and do the easier ones first.

 

Is it ok to cut about 3/4th of the vent tube ??

 

try this.start up bike and warm it up.Rev it up to the max rpm u want to go. if it works in nuetral then try putting it in to gear and at under half throttle run your bike up to the rpms u would like to go to.....if it goes to 8500 rpm at half throttle or less but doesnt go at full throttle this will tell u alot about ur jetting.

 

maybe it's taking air from somewhere????