bike wont accelerate past 40. help!

[brad020]

Similar problem

I am resurrecting a 250T as well, sounds similar. I can hit 50mph or so, but the engine seems like it's bogging above 5500rpm. You can feel a slight hesitation, like a (bigger) bike going from 4 cylinders down to 3. I would think if a twin dropped a cylinder, it would be more noticeable. I'm wondering about a valve spring floating or out of adjustment, poor mid-high range jetting, or an intermittent spark miss. Interested to see where this leads...

[Nessism]

Are their any modifications on the bike such as leaving the airbox off?

[brad020]

I am resurrecting a 250T as well, sounds similar. I can hit 50mph or so, but the engine seems like it's bogging above 5500rpm. You can feel a slight hesitation, like a (bigger) bike going from 4 cylinders down to 3. I would think if a twin dropped a cylinder, it would be more noticeable. I'm wondering about a valve spring floating or out of adjustment, poor mid-high range jetting, or an intermittent spark miss. Interested to see where this leads...

I was able to raise the jet needles, there was a spacer on top of the snap ring that should have been below the snap ring, and it helped a lot. I still feel a slight hesitation at high revs over 50mph, thinking maybe richen it up more and re-check the floats, and I should be all set. By the way, I have pod filters and stock exhaust, pilot jetting has been richened up.

[Mekanix]

What about the main jet?

Raising the needle didn't fix anything, more like the main is too small and your compensating by making the mid-range richer with the needle.

What does your plugs look like when you chop at high rpm?

[Billy Ricks]

Have the valves been adjusted and carbs properly cleaned. You need to start with the basics.