Hawk 250 PE28FL Jets?

[N7sithis]

I installed a PE28FL Nibbi and the stock main was a 112, I changed it out to a 110...now I'm thinking I should have went with a 105?

The nibbi and the matching Nibbi Air filter are the only mods that affect performance on the bike.

I live between 500-600ft above sea level

Bike sometimes has a hard time starting up for the first time, especially if it's chilly out (40-50 degrees), but after it's warm starts up fine every time.
I know nothing about bikes or carbs. does this sound like a jetting issue?

Also, is the plunger a "start assist" on this carb? So I pull it up to start the bike, then push it back down after it's running a minute or so? Coming from the stock carb that has a lever I'm a bit confused.

[XLsior]

main jet does not impact idle/starting it is metering 3/4 to WOT. Pilot jet for most users including myself is 38-40.

Im at 1000ft. Think i have a 118 main on 3rd needle clip. With a 38 pilot.

the air/fuel screw is about 1.5 turns out. should be between 1 and 2.5 range.
the idle screw adjustment should just be a crack open looking at the slide without the air filter installed.

the "start assist" enrichment circuit plunger takes up choke duty without needing a butterfly valve. It normally reseats with a throttle blip.

Cold starting seems to like a idle knob tweaked up a bit on my bike with idle then tuned on the fly when the engine is at running temp.

these settings should be close...but only used as general PE28FL carb tuning information.

[N7sithis]

main jet does not impact idle/starting it is metering 3/4 to WOT. Pilot jet for most users including myself is 38-40.

Im at 1000ft. Think i have a 118 main on 3rd needle clip. With a 38 pilot.

the air/fuel screw is about 1.5 turns out. should be between 1 and 2.5 range.
the idle screw adjustment should just be a crack open looking at the slide without the air filter installed.

the "start assist" enrichment circuit plunger takes up choke duty without needing a butterfly valve. It normally reseats with a throttle blip.

Cold starting seems to like a idle knob tweaked up a bit on my bike with idle then tuned on the fly when the engine is at running temp.

these settings should be close...but only used as general PE28FL carb tuning information.

Seems like it was just the Air/fuel screw! It was out way too far, screwed it all the way in and out 1.5 turns, then another .5 turn, she's started right up ever since, no problem! Thanks!

[N7sithis]

What should Idle be at on this bike? Mine seems to like 1700 ish but they seems quite a bit too high? Should be around 1000?

[XLsior]

my bike seems happy about 1100

[Megadan]

CG250 idle speed is 1500rpm plus or minus 100 rpm, aka 1400-1600rpm. Idle too low and it can affect oiling and be more prone to stalling.

[N7sithis]

CG250 idle speed is 1500rpm plus or minus 100 rpm, aka 1400-1600rpm. Idle too low and it can affect oiling and be more prone to stalling.

That's what I was hoping to read, Bike can handle that, I googled "Motorcycle Idle" and most said 1000-1300, bike didn't like it when I tried to lower it to 1000 ish.

[N7sithis]

Hey all, I'm bringing this thread back to LIFE!

I recently modded the bike more and it seems like I need new jetting...
I have the Nibbi 28FL, nibbi air filter, and now added an exhaust (The popular one everyone has lol) And an oil cooler (dunno if that affects jetting? Prolly not)

Still at 500-600 above sea level. I've noticed some popping from the exhaust after letting off the throttle. Not sure if I need to lower or raise the main jet? It's not as noticeable once the bike is warmed up but still a bit of popping.

Current main is still 110

My research is pointing to a 115 main, can anyone confirm?

Also curious as to what the pilot should be? Not sure what I have in there now, whatever the stock is.

[Megadan]

Main jet has nothing to do with decel popping. That would be the idle mixture mostly.

[N7sithis]

Main jet has nothing to do with decel popping. That would be the idle mixture mostly.

Oh, but I want the idle sitting at 1400ish RPMS, so adjusting it to fix that would mess up idle, no?
Maybe I'm just not letting it warm up long enough? I haven't taken it on a long ride in a while, just been short trips around the farm to test all the new stuff I've added, make sure nothing is leaking, etc.

So with exhaust and air filter would I not necessarily need to change to a 115 from 110?

[N7sithis]

I'm an idiot, I watched a video on "decel pops" and yeah, nothing to be worried about.

I'd still like to confirm jet sizes for this setup though, from what I found I should be running a 115/118 main and aaa...38 pilot?

[Megadan]

Oh, but I want the idle sitting at 1400ish RPMS, so adjusting it to fix that would mess up idle, no?
Maybe I'm just not letting it warm up long enough? I haven't taken it on a long ride in a while, just been short trips around the farm to test all the new stuff I've added, make sure nothing is leaking, etc.

So with exhaust and air filter would I not necessarily need to change to a 115 from 110?

Idle mixture and idle speed are two different adjustments.

[XLsior]

38-40 and 115-120 with a middle clip is a general safe sweet spot to begin with.

Having done mods myself my main jet might be creeping up into the 130s fairly soon.

[N7sithis]

Idle mixture and idle speed are two different adjustments.

Oh, I'm stupid, that's the screw at the bottom, not the knob lol

[N7sithis]

38-40 and 115-120 with a middle clip is a general safe sweet spot to begin with.

Having done mods myself my main jet might be creeping up into the 130s fairly soon.

Thanks, just for my own knowledge, why is it getting higher(from 120 to 130)? Just more mods to the bike or?

[XLsior]

Thanks, just for my own knowledge, why is it getting higher(from 120 to 130)? Just more mods to the bike or?


ported head, foam pod filter and higher flow exhaust...

Then the eventual jump with a 70mm piston 'big bore' kit increasing displacement volume.

I haven't noticed much performance difference in elevation changes 0-1000ft.

above 1000ft might be a different jetting situation.

[Megadan]

Thanks, just for my own knowledge, why is it getting higher(from 120 to 130)? Just more mods to the bike or?

More air = more fuel. with my ported head and cam I run a 38 pilot jet and a 145 main in my PE28.