ninjette.org - View Single Post - Horrible performance below 6K RPM, especially when warm. Video attached.

clakmurrick · November 21st, 2020, 12:55 PM

Hey all, this might be a cluster. Hopefully my ADHD mind won't screw this post up too much, I'll try to stay on track.

I had a buddy of mine help me find a 250R for dirt cheap. We checked it out and everything was fine, but it didn't run. The PO dropped the bike, didn't ride it for many months, and of course the carbs gummed up. We took the bike home and my buddy taught me how to rebuild the carbs. We cleaned everything thoroughly, including dipping it all in a tub of carb cleaner. I used little bread ties to poke the holes of all the jets and what not. I also removed the block plate for the idle mixture screws and adjusted them to 2.5 turns counter clockwise from the closed (tight, idk what to call it) position.

I should note that my friend convinced me to remove the stock airbox, so we replaced it with velocity stacks, and we removed the stock muffler and attached a SC Project exhaust.

In order to make use of these mods, we got a jet kit, which replaced the main and idle jet, and we also added washer spacers to the needles and cut the spring slightly, according to the instructions provided.

The bike has always ran a little odd, at first, when we had the modifications but no jet kit, the bike ran somewhat okay down low (sounding like it was breaking up), and it would not get above 7k RPM at all. We jetted the bike and then it was able to rev to redline and pull well. The only problem is that I still have horrible performance down low. The bike will idle and will start fine, especially when cold, but once the bike warms up, I can't make it through intersections without the bike bogging and dying on me. I have to rev it to 6k RPM minimum before taking off so it won't bog.

I have a video linked here that shows the behaviour once warmed, and this was an extreme event, because I literally could not rev past 3k. I will admit, that at this current time the idle mixture screws have been tightened almost all the way back, however I did this to test their function, and oddly it had no difference on the bike as far as I can tell since the bike was doing these same shenanigans before adjusting the idle screw.

Here's the video: https://www.youtube.com/watch?v=ovJGXEefjGw

I hope y'all will go easy on me, I learned my lesson to get the bike running right before modding it, my damn friend convinced me it would be alright!

November 21st, 2020, 12:55 PM	#1
clakmurrick carb newbie Name: Clark Location: Dallas, Texas Join Date: Nov 2020 Motorcycle(s): 2008 Ninja 250R Posts: 22	Horrible performance below 6K RPM, especially when warm. Video attached. Hey all, this might be a cluster. Hopefully my ADHD mind won't screw this post up too much, I'll try to stay on track. I had a buddy of mine help me find a 250R for dirt cheap. We checked it out and everything was fine, but it didn't run. The PO dropped the bike, didn't ride it for many months, and of course the carbs gummed up. We took the bike home and my buddy taught me how to rebuild the carbs. We cleaned everything thoroughly, including dipping it all in a tub of carb cleaner. I used little bread ties to poke the holes of all the jets and what not. I also removed the block plate for the idle mixture screws and adjusted them to 2.5 turns counter clockwise from the closed (tight, idk what to call it) position. I should note that my friend convinced me to remove the stock airbox, so we replaced it with velocity stacks, and we removed the stock muffler and attached a SC Project exhaust. In order to make use of these mods, we got a jet kit, which replaced the main and idle jet, and we also added washer spacers to the needles and cut the spring slightly, according to the instructions provided. The bike has always ran a little odd, at first, when we had the modifications but no jet kit, the bike ran somewhat okay down low (sounding like it was breaking up), and it would not get above 7k RPM at all. We jetted the bike and then it was able to rev to redline and pull well. The only problem is that I still have horrible performance down low. The bike will idle and will start fine, especially when cold, but once the bike warms up, I can't make it through intersections without the bike bogging and dying on me. I have to rev it to 6k RPM minimum before taking off so it won't bog. I have a video linked here that shows the behaviour once warmed, and this was an extreme event, because I literally could not rev past 3k. I will admit, that at this current time the idle mixture screws have been tightened almost all the way back, however I did this to test their function, and oddly it had no difference on the bike as far as I can tell since the bike was doing these same shenanigans before adjusting the idle screw. Here's the video: https://www.youtube.com/watch?v=ovJGXEefjGw I hope y'all will go easy on me, I learned my lesson to get the bike running right before modding it, my damn friend convinced me it would be alright!