Nibbi pe28 jetting help

[GaryF11]

Originally Posted by 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.

I understand all that but when at WOT in 5th after I let off and give it even like 1/8 throttle it chokes out and thay is the pilot circuit at that point but it only does that in 5th WOT has no symptoms at all and pilot circuit also has no symptoms until right after WOT when you try to give it gas again but only in 5th I mean it may be the main circuit but I’ve tried rejetting it I’ve ran these jets like I said between 45 and 75 degrees Fahrenheit and it’s currently 61 and it’s running like this

[severely]

Originally Posted by GaryF11

I understand all that but when at WOT in 5th after I let off and give it even like 1/8 throttle it chokes out and thay is the pilot circuit at that point but it only does that in 5th WOT has no symptoms at all and pilot circuit also has no symptoms until right after WOT when you try to give it gas again but only in 5th I mean it may be the main circuit but I’ve tried rejetting it I’ve ran these jets like I said between 45 and 75 degrees Fahrenheit and it’s currently 61 and it’s running like this

We can usually tell a lot about engine performance by examining the spark plug. Black is too rich, white too lean. Try re-reading JerryHawk250's post with a little less defensiveness and a little more open mindedness. Neither he nor I would bother posting unless we have reason to. I also suggest looking insider the air filter for restrictions, I've read about similar issues. Also make sure your fuel lines do not extend below the float bowl of the carb. Good luck.

[XLsior]

Sounds like the 40 tooth rear sprocket is to tall...
try changing to a 16t front from 17t

[GaryF11]

Ok third post about this let’s see if we can figure it out haha. Anyways my other posts were talking about how I usually max out at around 68-73 mph depending on the weather, I have been running 32/122 jets in a nibbi pe28 needle in middle position at sea level, I’ve been running this setup for months without having to tweak anything, we’ll starting about 2 weeks ago my bike will not run right I have went up and down on the jets and still nothing. It takes a while to start up and when it does it runs fine until 5th gear in 5th it feels super choppy it hesitates and if I give it WOT it’s fine except I can’t get it over about 62 mph even 4th gear goes faster than that 4th takes me to 64-65 mph so that doesn’t make sense and the biggest problem of all is if I am at WOT and let off throttle completely as soon as I try to give it a little bit of throttle again it chokes up and sputters and sounds like it wants to die .. I’ve tried everything everyone told me to try like check for water in the tank, check my fuel filter, check for restrictions on the air filter, I’ve tried taking the filter off completely and see it that changes, I’ve tried undoing the crankcase vent filter to see if that was clogged, I just readjusted my valves .004 intake side and .005 exhaust side, AND I JUST GOT A BRAND NEW SPARK PLUG NGK iridium to be exact, I’ve tried everything and still
nothing.. yesterday I tried going up on the jets went to 35/125 and still ran bad but I checked the plug and it was white so I went up again 38/130 still bad but it was rich the only weird thing is I’ve NEVER had to go that high on fuel I’ve always been around 32-35 on the pilot and 120/125 on the main. I just don’t know what it could be because at this point I don’t know how it’s running lean when it was running perfect on 32/122 for months nothing has changed with the weather it’s been between 50-70 Fahrenheit and I’ve ran those jets in colder and warmer temps. I am just lost I don’t know what to do the only thing I know is bad on my bike is the battery and an exhaust leak at the head because a stud broke off if that can cause what’s happening idk, anything y’all can think of that I haven’t done let me know anything helps I’m planning a pretty long road trip with my friend at the end of next month so I need this bike to run perfect. I’ll list my performance mods so y’all can see if anything is affecting it.
NIBBI PE28 carb, NIBBI FILTER, NIBBI HIGH SENSITIVITY THROTTLE, NIBBI IGNITION COIL, NGK IRIDIUM SPARK PLUG, JT 17/40 SPROCKETS, JT ORING CHAIN, FULL STRAIGHT PIPE, BOARD EXHAUST MANIFOLD, WIDER EXHAUST FOR MORE NOISE AND FLOW 1/34 inch, and a ton of cosmetic mods.

[JerryHawk250]

Okay, so you said your battery is bad. If it's not taking a charge and you are running the bike off the charging system on the engine then that could be your problem. Probably not getting a strong enough spark. Replace the battery.

[Sport Rider]

do you have the original coil to put back in it? my first thought is electrical. from watching your threads, this sure is baffling.

[XLsior]

just go back to a stock coil and CDI and see if anything changes.

[JerryHawk250]

Read his post to the end. He has a bad battery. The charging systems on these bikes aren't really design to run the bike without the battery. My battery on my Hawk recently died. The bike could be kicked started but if you hit the horn it would kill it and horn didn't really work. New battery and everything works perfect.

[XLsior]

Good to know regarding battery...Though I'm perpleaxed as to how the charging system is not adequate to run in limp mode...

However I'll keep in mind the horn check if the charge system is suspect...

My eyes could no manage to read the whole thing due to the massive paragraph structure...So i skipped the middle portion and just read the start and finish.

[GaryF11]

Originally Posted by JerryHawk250

Okay, so you said your battery is bad. If it's not taking a charge and you are running the bike off the charging system on the engine then that could be your problem. Probably not getting a strong enough spark. Replace the battery.

Well I bought a new battery and I installed it and still having the issue although it does feel way snappier like all the power loss I was feeling is gone now it feels normal except it’s still doing that choppy thing in 5th gear and I still can’t get over 64 mph 5th still feels low on power too at this point I don’t know what to do plug indicated still lean at 35/125 jets so I went 38/130 and it feels amazing running perfect except for 5th…

[XLsior]

why your problem is only in 5th gear to me suggests the gearing is to tall for your setup...

the engine only has so much power to give I think you're just asking to much of it.

[Sport Rider]

Originally Posted by XLsior

why your problem is only in 5th gear to me suggests the gearing is to tall for your setup...

the engine only has so much power to give I think you're just asking to much of it.

in my experience, it would bog down and not have enough power, but not the choking and sputtering he describes. I'm no expert with carbs though.

Perhaps just the main is too big and with power loss and excess fuel it's choking????

[Thumper]

This sounds like it could be a needle height problem.
Maybe it runs a bit lean at WOT. This would explain the symptoms of running OK until really challenged at the top end in 5th.

If you give it a ~1mm shim and it helps, then you are on the right track.

[Megadan]

2 known issues, including an exhaust leak at the head...

Good rule of thumb, fix the known issues because sometimes things that you think wouldn't cause a problem absolutely can, or can pile on with other issues. That is why Jerry is suggesting tonget a good battery installed. He is right about how these bikes behave with a bad battery.

[Megadan]

Also, do all of us a favor and quit making new posts. Keep it all in one continuous thread and just update it. This saves you from having to type 5 paragraphs, and gives everybody else easy access to all previous information and troubleshooting.

This is just constructive criticism, btw.

If you are worried people won't pay attention if it isn't new, don't even sweat that. People will stay on a thread as long as somebody keeps it active. I have threads that are 25 pages deep lol