Winter project; 250 engine

enko11 · November 17th, 2012, 09:09 AM

Hello everyone, I wondering if anyone is going to modify their ninja 250s this winter or has experience building them up. I have tossed up going turbo but im just sticking to a N/A high CR combo. Pulling the engine this weekend, hoping someone here can help me out with my engine build.

First is overboring, JE has a +2mm and +4mm overbore, does anyone know if the +4mm still leaves a good amount of room for maintenance later on? Also are the walls thick enough to support that.

EFI or race carb? Im thinking the Keihin CR series right now. Have not looked into upgrading the ignition if I go this route.

The crank. Anyone deal with getting it machined, how much weight can be shaved and does it affect the clutch or lubrication in general. Planned on having it knife edged into a tear drop also.

Aftermarket cams. The BEET camshaft seems to be the only option, anyone have any input on how it affected their powerband and low end / idle quality.
Anyone go with a custom cam profile also?

I am excited to have a high output 250 engine but would love some input especially with having the crankshaft machined.

And yes I know I could just buy a bike with a larger engine, just to get that out of the way.

I can see why a 500 engine swap is tempting, much cheaper route than building this engine up with its dismal aftermarket support.

Thanks for any support you can offer!

Racer x · November 17th, 2012, 09:24 AM

Is the bike going to be street strip or track? How much experience with modifications do you have?
All the answers to questions you have are some place on the forum. But I would be glad to answer what I can.
I have not done cams . But I have done rods,crank work, head work, pistons ,carbs, ignition system and nitrous on my 250 ninja.

subxero · November 19th, 2012, 09:18 AM

I'm planning on doing a basic piston swap this winter, nothing as intense as you describe. I am just planning on going to a higher CR, not overbore. But even with just a higher CR there is a lot of stuff that will likely need adjusted to get it to run smoothly.

As far as overbore, i am no expert but from what i have read you will need to get the cylinder sleeved or plated.....or something like that? I feel like if going higher than 250cc is non issue for you, you are way better off getting a 300 ninja then just do some basic performance mods to it.

If you are not overly familiar with 4stroke motorcycle engine and how to work on one and or don't have a decent amount of cash to just throw away paying for other people to do the work and your only reason for doing so is cuz you want a unique streetbike. I just think it is gonna be a PITA!!

I change my mind on my plans about just dropping new piston in and tuning because i think it is gonna be a PITA and has potential to mess up my perfectly fine engine if i get something slightly incorrect. But you are talking about complete heart surgery here with nothing to go on.

Just my 2 cents. Get informed the best you can and try and make a reasonable decision. For the cash you are talking i would be on a 300 in a heartbeat.

good luck, keep us informed, maybe start a blog if you go through with it

Racer x · November 19th, 2012, 02:43 PM

If you drop in a set of 12.5 to one pistons in a otherwise stock bike you will have no tuning issues. Even with an exhaust and pod filters .After a dyno session or a couple jet changes you will love it.

subxero · November 19th, 2012, 03:11 PM

Quote:

Originally Posted by Racer x

If you drop in a set of 12.5 to one pistons in a otherwise stock bike you will have no tuning issues. Even with an exhaust and pod filters .After a dyno session or a couple jet changes you will love it.

what about timing?

Racer x · November 19th, 2012, 03:58 PM

The stock timing is 35 deg. You could get more power with a few deg of timing. But going from 11.6 to 12.5 is not that big a jump in compression.

subxero · November 19th, 2012, 06:45 PM

Quote:

Originally Posted by Racer x

The stock timing is 35 deg. You could get more power with a few deg of timing. But going from 11.6 to 12.5 is not that big a jump in compression.

good to know, i will definitely want to squeeze out as much power as i can in the end but it is nice to know it will be rideable with out.

mgentz · March 29th, 2013, 01:14 PM

I wonder if this guy ever did any of this?

subxero · March 29th, 2013, 01:43 PM

Thinking not.

I think most people have big dreams... and thats about all they are especially after they realize how much work and money is involved.

My hat goes off to some of you guys, how and where you find time and energy to get all this work done.

I am still planning on doing my project, i have slowly been buying bits and pieces here and there as i squirrel away cash. I have everything i need except i have not bought the higher compression pistons yet, a little over $300 on ebay and a few odd and end things, tools ect..

Then i just need to find the time to tear into it.

Hopefully i take the time to document the mods and make something useful out of it.

November 17th, 2012, 09:09 AM	#1
enko11 ninjette.org member Name: Jimmy Location: Milwaukee Join Date: Apr 2012 Motorcycle(s): Ninja 250 White Posts: 11	Winter project; 250 engine Hello everyone, I wondering if anyone is going to modify their ninja 250s this winter or has experience building them up. I have tossed up going turbo but im just sticking to a N/A high CR combo. Pulling the engine this weekend, hoping someone here can help me out with my engine build. First is overboring, JE has a +2mm and +4mm overbore, does anyone know if the +4mm still leaves a good amount of room for maintenance later on? Also are the walls thick enough to support that. EFI or race carb? Im thinking the Keihin CR series right now. Have not looked into upgrading the ignition if I go this route. The crank. Anyone deal with getting it machined, how much weight can be shaved and does it affect the clutch or lubrication in general. Planned on having it knife edged into a tear drop also. Aftermarket cams. The BEET camshaft seems to be the only option, anyone have any input on how it affected their powerband and low end / idle quality. Anyone go with a custom cam profile also? I am excited to have a high output 250 engine but would love some input especially with having the crankshaft machined. And yes I know I could just buy a bike with a larger engine, just to get that out of the way. I can see why a 500 engine swap is tempting, much cheaper route than building this engine up with its dismal aftermarket support. Thanks for any support you can offer!

November 17th, 2012, 09:24 AM	#2
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	Is the bike going to be street strip or track? How much experience with modifications do you have? All the answers to questions you have are some place on the forum. But I would be glad to answer what I can. I have not done cams . But I have done rods,crank work, head work, pistons ,carbs, ignition system and nitrous on my 250 ninja. __________________________________________________ Top speed 123.369mph. Ohio mile Worlds fastest 250 ninja

November 19th, 2012, 02:43 PM	#4
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	If you drop in a set of 12.5 to one pistons in a otherwise stock bike you will have no tuning issues. Even with an exhaust and pod filters .After a dyno session or a couple jet changes you will love it. __________________________________________________ Top speed 123.369mph. Ohio mile Worlds fastest 250 ninja

November 19th, 2012, 03:58 PM	#6
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	The stock timing is 35 deg. You could get more power with a few deg of timing. But going from 11.6 to 12.5 is not that big a jump in compression. __________________________________________________ Top speed 123.369mph. Ohio mile Worlds fastest 250 ninja

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November 19th, 2012, 09:18 AM	#3
subxero dirty boy Name: Joe Location: Johnstown, PA Join Date: Sep 2012 Motorcycle(s): I don't even know anymore?? Posts: A lot. MOTM - Apr '14	I'm planning on doing a basic piston swap this winter, nothing as intense as you describe. I am just planning on going to a higher CR, not overbore. But even with just a higher CR there is a lot of stuff that will likely need adjusted to get it to run smoothly. As far as overbore, i am no expert but from what i have read you will need to get the cylinder sleeved or plated.....or something like that? I feel like if going higher than 250cc is non issue for you, you are way better off getting a 300 ninja then just do some basic performance mods to it. If you are not overly familiar with 4stroke motorcycle engine and how to work on one and or don't have a decent amount of cash to just throw away paying for other people to do the work and your only reason for doing so is cuz you want a unique streetbike. I just think it is gonna be a PITA!! I change my mind on my plans about just dropping new piston in and tuning because i think it is gonna be a PITA and has potential to mess up my perfectly fine engine if i get something slightly incorrect. But you are talking about complete heart surgery here with nothing to go on. Just my 2 cents. Get informed the best you can and try and make a reasonable decision. For the cash you are talking i would be on a 300 in a heartbeat. good luck, keep us informed, maybe start a blog if you go through with it

March 29th, 2013, 01:14 PM	#8
mgentz Board Member Name: ... Location: WI Join Date: Dec 2011 Motorcycle(s): 250R (street), 250R (dirt) Posts: A lot.	I wonder if this guy ever did any of this?

March 29th, 2013, 01:43 PM	#9
subxero dirty boy Name: Joe Location: Johnstown, PA Join Date: Sep 2012 Motorcycle(s): I don't even know anymore?? Posts: A lot. MOTM - Apr '14	Thinking not. I think most people have big dreams... and thats about all they are especially after they realize how much work and money is involved. My hat goes off to some of you guys, how and where you find time and energy to get all this work done. I am still planning on doing my project, i have slowly been buying bits and pieces here and there as i squirrel away cash. I have everything i need except i have not bought the higher compression pistons yet, a little over $300 on ebay and a few odd and end things, tools ect.. Then i just need to find the time to tear into it. Hopefully i take the time to document the mods and make something useful out of it.