ported engine jetting

[jimjim]

Just got my 02 300 engine back in,it has been ported and I run a pod filter set-up.Ran it with old carb jetted 178 main,40 pilot,a/s 2 turns out,as1,#7 slide stock needle.It runs awful,burbles & bogs low clears very slightly in mid.I know I need a better needle any Idea on a baseline to start? Any help would be great!

[lonetree]

i have two 09, a 250 and a 300.... only head work, no porting...
stock needle is crap throw it away....
i love n3XX needles, (ktm sx 250 mods and yammie 250 mods needles)..
i run 38/182 n3eg- 250 and 38/182n3ec? i think needle in the 300..
ndew needles (suzi) also work well but compleatly different feel....

my 04 300 also ran very similar settings... in OZ btw...

[motopsycho87]

Try the jetting in my sig, from experience, the more you tune a 2 stroke, the leaner the jetting wants to be (this is due to increased intake velocity actually drawing in more fuel).

[jimjim]

Update.For whatever reason the engine likes the clip on the top of the needle,cleaned it up a lot,still going to try the Yamaha needle.

[motopsycho87]

Mine is the same

[jimjim]

Update;went with a n3eg needle clip @ top,38 pilot,170 main a/s 3/4 turn out.Runs like a beast from 1/4 throttle up,below that its like a 4 stroke hitting the rev limiter in sound and feel.I don't know if its a lean or rich situation,any ideas?Thanks.

[Jakobi]

At top clip and that small main you could be (are likely) lean.. The bottom end sounds rich. Burble burble burble snap!

Based off what you have said (and if everything else is in order; pv, timing, reeds, etc) I'd aim at going richer on the needle clip, but with a leaner diameter to clean up the off idle response. What number slide?

[jimjim]

Thanks for the reply.Yes I have checked PV reeds are new.I think you are right,burble and rockets off like a light switch on or off.I am running a #7 slide.Are you saying to try another needle?

[Jakobi]

How did the bike run in say 2nd/3rd clip position, once above say 1/8 - 1/4 throttle?

I would try a needle with a leaner diameter, but exactly which one will take some testing and it will be a combination between pilot and diameter.

[jimjim]

Progressively worse on every clip position down.I am calling uncle,taking the bike to the shop that built the engine,getting the carb bored to a 40mm and they will tune it.I got my 250 running good with the jetting,just cant get this 300 diled in.I will post results.