Jetting help after porting

[sand-paddles]

Rebuilt a new engine and now runs poor.

 

My old engine had T5 pipes, Vforce 3 reeds, pod filters, +4 timing bored out .040,135 psi compression, stock carbs. This engine ran great with 280 main and needle in 4th position

 

Rebuilt a new engine using all the old parts except I'm now running ported cylinders and 185 psi compression. I changed the main jet to 330 and it ran terrible. Slowly worked my way down to a 290 with the needle in the second position and it now runs better, but from 1/4 throttlet to 1/2 throttle it still seems rich.

 

If I dump the clutch with the engine in the higher rpm it takes off great.

 

Is it possible my jet sizes stayed the same going from stock port cylinders to ported cylinders? Any help on what I need to do to get rid of the dead spot just above idle?

Edited March 14, 2016 by sand-paddles

[Larry's Shee]

Who did the porting? Any info? Timings or "style" ? What pilot, needle clip ?

[Surfrjag]

did you add some ignition timing to it?

your jetting should be around 330

also did you do a leakdown test when you assembled the motor?

[sand-paddles]

The cylinders have dj racing engraved in them, but that's all I know about who ported them. It has a 25 pilot, and I believe toomey needles.

 

I set the timing back at +4 degrees. I did not do a leak down test.

 

Yes I changed to straight Vp110 fuel mixing oil at 32:1

[camp0429]

Try bumping up your pilot to 27.5 or 30, it may even like a fatter pilot. With stock carbs, ported stock cylinders and pods mine liked a 35

[sand-paddles]

What elevation are you at? I'm around 4500-5000 ft

[camp0429]

What elevation are you at? I'm around 4500-5000 ft

Didn't think about that. Im around 600