Reply To: Jetting a 2009 carby gt250
I would 1000% avoid having pods on a hyosung. You will be in a long abyss trying to make it happy afterwards.
Sorry for the sour news , but really i have tried many setups , the carby motors run best with their airboxes on.
Why not just fit K&N 6507 Air Filter. Mind you, the Stock GT250 air filter is the same as the 650, and the carby 250 airbox has more than enough air capacity to run a 650 too.
What’s the restriction in air ? – The silencing cones that’s inside the air filter, that’s why K&N air filter is just an open hole without the noise suppressing one inside.
I don’t know about USA but here in UK, we don’t really like the sigma kits (wishy washy, and sometimes they make you make modifications to carbs we don’t like, like drilling things etc, it’s very silly).
Is there a local Mikuni dealer around you or any bike shop that deals with Mikuni carbs ? – Get 95 Main Jet Front and 97.5 rear = This is the most max setup. Going beyond 97.5 is wasted fuel really, the bike won’t see much dyno gains after that.
Take a look at these carb links for best set up for your bike
[Tutorial] How to adjust Carb Slide Needle (Tuning) – Hyosung GV & GT 125/250
and this one
[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250
Also, this is hard to ignore ,but “you will notice this” – Get a FULL Size exhaust can (muffler) and make sure it has baffle.
Zero Baffle = Higher top speed (maybe 2-3mph extra) , same with the 125cc here in UK
Baffle included = More low end torque
Modify baffle (make the baffle have smaller hole about the dimensions of a 10 Pence british coin) , bike has better acceleration overal.
Baffle = aka. DB Killer.
Why I said to use “Full Size” cans/mufflers, it is because “tiny” ones or “shorty” ones are pointless and extra loud with no real gains. (no backpressure for a heavy twin that needs a little thrust to set off from 0mph)
Full Size Muffler is similar to size of the stock Hyosung GT250 muffler
Hope this info helps, just my 2 cents 😀
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