Nibbi pe28 jetting help

[GaryF11]

Hey not sure if y’all are tired of me asking questions about jetting yet haha but anyways I recently installed a pe28 and got rid of my problematic pe30 the bike was running perfect absolutely 0 complaints on a 38 pilot and a 128 main needle in the notch right below the middle. Anyways about a week ago it started acting up really bad and I haven’t been able to sort it out so my question is what are y’all’s getting recommendations for my bike with my mods. Here’s the mod list: full straight pipe, nibbi pod filter, nibbi intake tube, nibbi pe28, nibbi high sensitivity throttle, 45 rear sprocket, 17 front sprocket, as well as a ton of cosmetic mods. PS I LIVE AT SEA LEVEL AND THE HIGHEST THE BIKE WILL GO IS OVER A BRIDGE OR SOMETHING WEATHER IS USUALLY AROUND 60

[Megadan]

May be an ignition issue and not the carb. Symptoms can sometimes be mistaken.

Is it a specific throttle position it does it at? A certain scenario that trips it up?

That said, the main may be a tad rich for your mods, even at sea level, and I have never needed either of my nibbis that rich on the needle either.

[XLsior]

Im leaning in the same direction as Dan,
My inkling would be the CDI.

spare coil, CDI and plug is always handy and wont break the bank.

Another possibility is fuel contamination.

If the bike was running fine on the current jets...then it starts playing up, its unlikely the current jet sizes are the issue.

[alex_in_az]

Originally Posted by XLsior

Im leaning in the same direction as Dan,
My inkling would be the CDI.

spare coil, CDI and plug is always handy and wont break the bank.

Another possibility is fuel contamination.

If the bike was running fine on the current jets...then it starts playing up, its unlikely the current jet sizes are the issue.

+1 on the CDI, get at least 2 of them, quality is hit or miss

[GaryF11]

Hi I have a 2021 hawk 250 before I start I’m going to list my mods to give you a better idea as to what proper jetting should be: nibbi PE28 carb, nibbi ignition coil with njk boot and njk plug, nibbi intake, 17/40 sprockets, nibbi high sensitivity throttle, Amazon oil cooler, full straight pipe no cats, adjusted valves to .04 and .05, bored out exhaust manifold, went to 10w40 oil, and a ton of cosmetic mods. Anyways I’ve been running 35/122 jets for a while now and the temps have been between 55 and 75 at seal level needle in middle position air fuel screw 1.5 turns out. The bike has ran amazing for the past couple months top speeds being between 68-73 mph no hesitation bogging or stumbling until a few weeks ago it started giving me nothing but issues. First it didn’t want to start at all one day no matter what I did it would not hold an idle and then it went back to being normal the next day ever since then it feels like the jetting is way off I readjusted my valves rejetted it multiple times and it’s still acting wonky I went back to the 35/122 and it won’t go past 57 mph 5th gear is useless at this point as 4th will take me to 60 and then 5th lowers me back down to 57 if I’m in 5th giving it more than half throttle and I let off my he bike chokes up really bad for a few seconds. Anyways I’ve tried really everything and can’t get it to run right now don’t know what’s going on I’m assuming just something with the jetting maybe I’m just dumb but 35/122 worked perfect for months and now I just can’t dial it in I tried 38/125 and it worked for a day or so until it really didn’t like that jetting. Anyways any input helps thanks.

[bogieboy]

Stupid questions.... did it start acting up after filling up with fuel, or right after a storm? Sounds kinda like water in the fuel to me, or bad fuel....

[Thumper]

Long shot, but might be the fuel filter. Also, when you had the carb out did you check on the needle valve that the float opens? Could be some crud there.

The fact that you had it running great does suggest you had the jetting right.

It doesn't sound electrical but the spark plug may have gone out of resistence range. I know, these seem like unlikely things, but you already worked on jetting (which shouldn't be off), and even went to the trouble of checking the valves.

Back firing might suggest fuel blockage (either the filter or the float bowl not filling). Do you notice back firing when it acts up. Also, if you let it sit for a few minutes, does it run right all of a sudden?

Also, is the head-pipe right at the head getting too hot (indicates lean mixture as well).

[GaryF11]

Ok so I should’ve also mentioned it backfires like crazy even when running right because I have an exhaust leak. Also I’ve installed a brand new fuel filter so it shouldn’t be that it was running amazing with it and it hadn’t been in that long.
And it acts up all the time whether the bike is low or full on fuel and it doesn’t matter where I get the fuel from I have checked and the float bowl does fill normally. Th weirdest part is that it doesn’t feel weird until I get above 50 mph and then it feels like I’ve lost half the power and it won’t go past 57 if i let off the throttle while giving it more than half it wants to start tweaking out. But it did storm a few days recently I keep my Hawk in a shed but it was outside for a few min in the rain water may have gotten in the fuel but I doubt it sounds like I should properly probably drain it and put new gas in it.

[Megadan]

Failing cdi or ignition coils also exhibit many of these same symptoms and are often mistaken for a fueling issue.

Just my 2 cents. Put the jetting back to where it was before it all started and change your focus to the ignition system/components. With simply making sure the pins are clean, dry, and inserted all fhe way into the connectors.

Plus, a cdi is fairly cheap, and so is a coil. Even if they don't turn out to be bad, having spares is not a bad thing with cheaper components.

Another thing to check/try if you haven't yet. Remove the air filter and see if anything changes. Some of these pod filters on the market can be fairly crappy. There was a member here that had similar problems after installing a filter. I had him check it and the neck of the filter had a ring of thin rubber choking it off more than halfway.

[Thumper]

Yes. CDI (or coil) may be the problem. My Templar X runs really great, idles perfectly, strong power band...then all of a sudden dies with cracking and popping while I slow down in gear. If I pull the clutch, stalls instantly. But if I wait a minute or two, it will start again. This began about 15 starts ago. Seems like it got worse before I parked it for troubleshooting. I thought fueling, but I ordered a CDI after ruling out carb issue.

Last garage test, it seemed to have FIXED ITSELF! But I am sure it will do this again eventually. Yes. Sounds like an electrical thingy now!

Transient problems are the worst! Coil will be next...I am even thinking maybe a stator wiring (transient short/crossed wire), but CDI was my next in line culprit!

It is on the way.

EDIT: I found the problem... my air mixture screw was too far out (it is an airscrew on the OEM carb on the Templar X). I closed it up (less air) and it runs perfectly now).

[GaryF11]

Well the ignition coil is pretty much brand new and it’s a nibbi so I doubt the coil is bad BUT the ngk plug is still the same spark plug that came with the bike when I bought it used so maybe the spark plug is just bad now… could be out of gap? Maybe? As for the CDI I’ve been trying to find one but every one that I look at that says it fits the Hawk the reviews say it broke or didn’t work right or retarded the timing so much that it broke the bike… sooooo anyone have any links to a somewhat affordable CDI that won’t break my bike?

[GaryF11]

Also this is the air filter I’m running if anyone knows anything about it or thinks this could be the reason the filter is brand new NIBBI Motorcycle Air Filter,Universal 48mm Dirt Bike Air Filters,Fit Motocross Carburetor Cleaner for Pit Bike Scooter Moped YAMAHA HONDA SUZUKI KAWASAKI ATV (48mm-Silver) https://a.co/d/85w0omB

[GaryF11]

Ok so I made a post yesterday about this and got some replies but I realized I wasn’t very specific at all about what is going on so let me be as clear as I can in this post. I have a 2021 hawk 250 about 2.5k miles on it changed oil regularly adjusted valves periodically I keep up with the maintenance on this bike (just had to put that out there) Anyways my hawk is modded out I have everything done that you can do besides big bore kit and porting the head and a few other little things but all the main performance mods I had done (nibbi pe28, nibbi intake, nibbi ignition coil, ngk spark plug and boot, oil cooler, breather filter, fuel filter, cat delete, board exhaust manifold, and 17/40 sprockets) im currently running 35/122 jets needle in middle position as that’s what I’ve been running for about a month now outside temps ranging from 40-75 degrees F at sea level and it always runs like a champ reaching top speeds of 69-73 mph. NOW FOR THE PROBLEM about a week ago my bike started acting up in the weirdest way it will start and run perfectly fine UNTIL you get to 5th gear 4th will take me all the way to 65 mph and then 5th just loses all power usually in 5th I can cruise at 60 and now it won’t let me cruise at anymore than 48 unless I’m holding wide open throttle (but in 4th I can cruise fine) if I am WOT in 4th at 65 and shift into 5th it just starts decelerating until about 57 and that’s where 5th stops about 57-59 mph. I HAVE TRIED EVERYTHING rejetted it, messed with the fuel screw, cleaned the spark plug, cleaned the breather filter, drained and refilled tank with new gas, made sure chain was tight, and it still is acting up also forgot to mention if you are WOT in 5th and let off and try to give it even the tiniest amount of throttle it will start choking up almost sounds like it’s way too rich and wants to die except IT RUNS PERFECT UNTIL 5th so too rich couldn’t be the case at least I don’t think… I was told water in the tank and that’s not it I was told bad ignition and that’s not it so I’m completely lost. I hope this was all easy to understand and any input helps please and thanks.

[GaryF11]

Yes I’ve tried taking the air filter off to see if it helps and still nothing

[JerryHawk250]

At WOT you should only be messing with the main jet. Pilot jet and idle mixture screw has nothing to do with WOT. With that said I had the same issue with my hawk. Air temperature has a lot to do with it. I usually have to rejet between winter and summer. I had to drop to a smaller main jet in the winter month because i was running too rich. Try to a 115 or 118 main.