Get FCR 35 carbs. A true flat slide and accelerator pump.

Get CR 31 carbs. Cheaper. Still bettter tune/power/response.

Stay with the crappy stock CV carbs.

Will you be riding this on the street or track?

What are the engine specs.

Both.

I have a build thread...but I'm on my phone and can't post the link.

Look at post #10. There are a few updates to the list but you will get the jist.

http://www.ninjette.org/forums/showthread.php?t=126445

IDK? but as I was working on my dirtbike yesterday I was wondering if it would be possible to link up 2 individual dirtbike carbs to work on the ninja250?

Reason, 2 used dirtbike carbs could be found and had for cheap, they are slide carbs.
I think it could be done but the only thing I would be unsure of is fuel delivery to the carbs. How would you ensure that both get the same? and at that point does it just work off of the cycling of the engine?

IDK
Just a random curious thought I had the other day

P.S. not trying to hijack

Look at post #10. There are a few updates to the list but you will get the jist.

http://www.ninjette.org/forums/showthread.php?t=126445

I got through enough of your build thread to see where you are going with it, I'll keep reading...

I know you commented on not going F.I., but it may be an advantage from a tuning standpoint if they are available in the size you are looking for. It could be a real challenge, but are there any current F.I units out there from a 4cyl in the size you want that could be adapted?

What is the cost difference between an aftermarket F.I. system and the carbs? What is Racer-X using?

EDIT: There must be a way to calculate the proper venturi size you want based on displacement and max RPM I would think. Too big and it could easily become a pain on the street or just not run well at lower RPMs and moderate throttle openings

I have used the 31CR carbs for a number of years. Though I got 34 HP numbers from the stock carbs. The ability to fully tune the carbs without removing the carbs is critical for racing.Plus I would never use nitrous with CV carbs.

I am very curious how the FCR carbs work.

For my turbo bike I am using FI. But have not run the bike yet.

IDK? but as I was working on my dirtbike yesterday I was wondering if it would be possible to link up 2 individual dirtbike carbs to work on the ninja250?

Reason, 2 used dirtbike carbs could be found and had for cheap, they are slide carbs.
I think it could be done but the only thing I would be unsure of is fuel delivery to the carbs. How would you ensure that both get the same? and at that point does it just work off of the cycling of the engine?

IDK
Just a random curious thought I had the other day

P.S. not trying to hijack

I have FCR carbs on my dirt bikes too. I like the way they operate and they are SUPER easy to tune and change.

As for FI, I am not totally for or against it. However, I would start with the $400 - $700 for carbs that I know I can tune. Plus, the venturi are larger and should offer more flow = more hp at high rpms.

The FCR got my vote the accelerator pump is the main advantage IMO

Just one more thing about the carbs. I have done a lot of different stuff with my bike. I have a full set of jets and needles . Plus some air jets. I think i have spent about 300 dollars on jets.
That is why I have not switched to fI for my nitrous bike.

Do you like the needle that comes with the carbs?

Anyone else? Does anyone use the fcr's?

so....31's then?

IDK? but as I was working on my dirtbike yesterday I was wondering if it would be possible to link up 2 individual dirtbike carbs to work on the ninja250?

Reason, 2 used dirtbike carbs could be found and had for cheap, they are slide carbs.
I think it could be done but the only thing I would be unsure of is fuel delivery to the carbs. How would you ensure that both get the same? and at that point does it just work off of the cycling of the engine?

IDK
Just a random curious thought I had the other day

P.S. not trying to hijack


The CRF150R uses a 32 mm FCR carb. I was thinking along the same lines as you and trying to use them. Between synchronizing them and the cost of a used pair you would be better off buying the kit for the bike.