Jetting for 2007 EC300 - something isn't right

[BIGSTEVE]

Hi everyone,

I am currently struggling to understand what's going on with my bike. It runs well enough to ride but something is definitely off.

So I live in Colorado and usually ride around 8k-10k elevation, 60-80 defF. When I got the bike a year ago it was clearly jetted for lower altitude. Been trial and erroring it, it still feels very rich despite running very lean jets. On my pwk38 I am running a 30 pilot, 155 main, needle in lowest position, air screw 3 turns out, and it still starts very easy and gives a fair bit of spooge and gets very poor mileage, even at lower elevation near Denver (~5800 ft). It has okay torque down low but lacks the snap I feel on other 300s of a similar vintage, and bogs hard near the top of the midrange, won't get over ~6.5k revs or so without clutch work.

I recently redid the top end (piston and rings, cylinder looked decent) and that helped but did not solve. Also have a new fmf turbinecore 2 silencer so exhaust packing is a non-issue. Air filter is clean and in good shape. Am I missing something?

Let me know what you all think! Not sure if it matters but I mix 40:1, and after replacing the silencer most of the spooge comes from the vent tube on the side of the cylinder near the exhaust port.

[SS109]

Have you done a leakdown test?

[(F5)]

My advice is as always.. clean tank above carb to stop dirt.

Carefully remove the needle and delicately with some sturdy linesman pliers
Cut it in half.


That will stop using the N1FE needle.

Read other jetting threads but the needle is fundamental. I'd get back richer on the other jess at same time, probably 40 and 170