636 fork conversion- steering stem welded in?

joes280 · June 23rd, 2011, 04:24 PM

I've seen a couple of indonesian 250's and a guy on stuntlife do the swap. From what I see the 08 stem is welded in. From other bikes I know they are pressed in. And you can swap them usually.

Just wanted insights before I started hackin ish. Anybody got any info, just don't wanna reinvent the wheel unless I have to.

Alex · August 14th, 2011, 01:43 PM

Did you make any progress on this?

extremez31 · April 11th, 2012, 10:21 AM

interesting, I have a complete 636 front end which i started to use on on a gs400 Cafe build. its tempting but im not sure if its such a good idea. The brakes are insane, also the front 636 rim is wider than the ninja rim. I believe the pregen rear rim is 2.5 inches wide and the 636 front is 3 inches. would having a wider front rim than rear rim affect handling?

the 636 front takes a 120 wide and the ninja rear takes a 130 wide. I suppose you could strong-arm a 110 on the 636 front but i think handeling would be affected more than anything.

I suppose i could just mount a single caliper and rotor which is still probably too much but would feel safer.

Anyone have any input?

Jono · April 11th, 2012, 06:39 PM

Mmmhm. Doesn't seem worth it to me. And it would just look weird!

kamikaze · April 13th, 2012, 08:36 AM

Quote:

Originally Posted by extremez31

interesting, I have a complete 636 front end which i started to use on on a gs400 Cafe build. its tempting but im not sure if its such a good idea. The brakes are insane, also the front 636 rim is wider than the ninja rim. I believe the pregen rear rim is 2.5 inches wide and the 636 front is 3 inches. would having a wider front rim than rear rim affect handling?

the 636 front takes a 120 wide and the ninja rear takes a 130 wide. I suppose you could strong-arm a 110 on the 636 front but i think handeling would be affected more than anything.

I suppose i could just mount a single caliper and rotor which is still probably too much but would feel safer.

Anyone have any input?

120 front would prolly be ok if you went with a 140 or 150 rear.

extremez31 · April 13th, 2012, 09:50 AM

But thats the thing, I wouldn't want to increase the rear tire width on the ninja. I love the way it rides. If the bike was putting out 42-50 hp a 140, 150 tire would be welcomed. Truth is any of those changes would hurt the ninja, it'll look cook.

Kevin2109 · April 13th, 2012, 11:54 AM

Do a 140, thats the ideal size for this bike, gives you just enough rubber to use

csmith12 · April 13th, 2012, 12:09 PM

Quote:

Originally Posted by Kevin2109

Do a 140, thats the ideal size for this bike, gives you just enough rubber to use

+1

extremez31 · April 13th, 2012, 12:14 PM

Thanks for the replies. What tires would you recommend on the pregen 250? I do want to do some trackdays so more emphasis on sport riding.

I need some rule books on the fork conversion, this would look pretty but i have a feeling it will put me up against some serious bikes.

Dampening should be ok as the bikes are not too far apart in weight. I may just do this...

duckracer · April 13th, 2012, 05:00 PM

I have done this conversion (pic's of Duc-asaki) will be posted in another thread soon. I used a Yamaha R1 front that I had lying around. So, yes the 250 triple clamp stem is press fit, then welded in, but only at the bottom. You grind the weld down and press the stem out. The 636 stem is the same size as the R1 stem. But it is aprox 1/4 inch larger diameter than the 250 stem. So you need to weld up the 250 stem larger than the press fit for the 636 lower clamp, then turn it down to a 1 to 2 thousands interfearence fit. Heat the lower clamp and cool the stem then press them together and your lower is done (you can't weld them as the stem is steel and the clamp aluminium).
The upper clamp has a smaller diameter seat so that will need to be milled to provide the correct stack height. That is all the machining you should need.
The front tire is now a 120/70. I run a single caliper and have more than enough stopping power. On the rear I am running a 17 inch new gen wheel with a 140 tire. Keep an eye open for the new thread and you will be able to see how I eliminated the rear caliper torgue arm. My rear caliper is mounted with a one off caliper mount/wheel spacer that retains the caliper vie the swing arm top and bottom.
The turn in will be just a tad slower with the bigger tires. That is easy to fix by raising the rear or lowering the front. I have my forks set 10mm from the top triple and the turn in now matches my Ducati 1098 race bike.
So this is a good conversion, but for most racing orgs it will be illeagle and push you into 250 superbike. Check your rule book. My org's 250 lw gt is a run what you brung 250 only class so mine is accepted

gt_turbo · April 16th, 2012, 01:24 PM

@duckracer what did you do with the ignition switch? i am working on a 636 front conversion on my 09 250r, the 250 ignition seems too small to fit the 636 triple.

extremez31 · April 16th, 2012, 01:27 PM

I think using a 636 ignition and key would be the simplest solution

gt_turbo · April 16th, 2012, 01:38 PM

Quote:

Originally Posted by extremez31

I think using a 636 ignition and key would be the simplest solution

i thought about that, but not sure if the connector between the two bikes would fit or not. if it doesn't then i'd have to splice it up, but i'm trying to keep it as close to stock if i want to go back. plus carrying 2 different keys for the ignition/tank is something i want to avoid.

duckracer · April 16th, 2012, 05:00 PM

Sorry, been busy. I used the stock ignition switch. The R1 top triple just needed to have the ignition switch hole bored out slightly, and I added longer bolts with spacers made from aluminium round stock. After I locktited the bolts I ground the heads to help prevent theft. The cool thing is the steering lock feature still works. Most ignition switches use a standard bolt pattern since the factories usually don't make them, and source them from an outside vendor. Unless you buy a Ducati then like me you are screwed! Damn Italians!!!! The 250 ignition switch has a plastic cover that can be removed and it would probably fit as is, but the plastic cover makes the switch look better. If you don't have access to a mill or lathe you could use and dremel to open the hole.

gt_turbo · April 16th, 2012, 05:24 PM

I have the opposite problem, the 250r ignition is about a quarter inch too small than the 636 triple. I'll have to find some thing to fill the gap. Rubber gromet maybe.

How do you try to retain the stock 250r geometry with the fork conversion? Is it like measuring the fork length from axle to top of the triple tree and trying to keep that distance? Unfortunately I did not measure anything before i dis-assembled.

duckracer · April 16th, 2012, 07:43 PM

The geometry will be way different. You are going to have a lot less fork offset with the 636 front end. This will give you more trail and make the bike hold a line really well. I use rake and trail as well as swingarm angle to set my race bikes up. But you can plan on having around 10 to 15mm of fork above the top triple clamp. This is because you have less fork offsett and the forks will be standing up more straight than stock. Just start at around 10mm and make sure you have front wheel clearence, then raise of lower the forks untill you get the turn in where you like it and gives you good feedback.

June 23rd, 2011, 04:24 PM	#1
joes280 ninjette.org member Name: joe Location: virginia Join Date: Oct 2010 Motorcycle(s): 250 Posts: 78	636 fork conversion- steering stem welded in? I've seen a couple of indonesian 250's and a guy on stuntlife do the swap. From what I see the 08 stem is welded in. From other bikes I know they are pressed in. And you can swap them usually. Just wanted insights before I started hackin ish. Anybody got any info, just don't wanna reinvent the wheel unless I have to.

August 14th, 2011, 01:43 PM	#2
Alex ninjette.org dude Name: 1 guess :-) Location: SF Bay Area Join Date: Jun 2008 Motorcycle(s): '13 Ninja 300 (white, the fastest color!), '13 R1200RT, '14 CRF250L, '12 TT-R125LE Posts: Too much. Blog Entries: 7	Did you make any progress on this? __________________________________________________ Montgomery Street Motorcycle Club / cal24.com / crf250l.org / ninjette.org ninjette.org Terms of Service Shopping for motorcycle parts or equipment? Come here first. The friendliest Ninja 250R/300/400 forum on the internet! (especially Unregistered)

April 13th, 2012, 11:54 AM	#7
Kevin2109 KThanksBye Name: Kevin Location: Orange County Join Date: Mar 2011 Motorcycle(s): 2006 zx636r Posts: A lot.	Do a 140, thats the ideal size for this bike, gives you just enough rubber to use __________________________________________________ ----> My Youtube! <---- Unregistered, watch my youtube page!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Steering stem bearing	justdrew	2008 - 2012 Ninja 250R Tech Talk	3	February 5th, 2015 07:57 AM
RAM on Steering Stem?	headshrink	2008 - 2012 Ninja 250R Farkles	15	May 30th, 2014 06:28 PM
Inverted fork conversion	old3	2013 - 2017 Ninja 300 Tech Talk	69	February 15th, 2014 07:41 PM
Upside down fork conversion from 636 bolt on	joes280	Motorcycle-related	46	April 11th, 2012 05:58 PM
steering stem nut	snowfish	2008 - 2012 Ninja 250R Tech Talk	2	April 14th, 2010 07:12 AM

April 11th, 2012, 10:21 AM	#3
extremez31 ninjette.org member Name: Rich Location: New Jersey Join Date: Apr 2012 Motorcycle(s): 94 EX250, 81 GS450 Posts: 67	interesting, I have a complete 636 front end which i started to use on on a gs400 Cafe build. its tempting but im not sure if its such a good idea. The brakes are insane, also the front 636 rim is wider than the ninja rim. I believe the pregen rear rim is 2.5 inches wide and the 636 front is 3 inches. would having a wider front rim than rear rim affect handling? the 636 front takes a 120 wide and the ninja rear takes a 130 wide. I suppose you could strong-arm a 110 on the 636 front but i think handeling would be affected more than anything. I suppose i could just mount a single caliper and rotor which is still probably too much but would feel safer. Anyone have any input?

April 11th, 2012, 06:39 PM	#4
Jono ninjette.org certified postwhore Name: Jono Location: Memphis, TN Join Date: Sep 2011 Motorcycle(s): 2009 Triumph Street Triple, 2009 KLX250SF, 2003 Suzuki SV650S (Sold), 2006 Ninja 250 (Sold) Posts: A lot.	Mmmhm. Doesn't seem worth it to me. And it would just look weird!

April 13th, 2012, 09:50 AM	#6
extremez31 ninjette.org member Name: Rich Location: New Jersey Join Date: Apr 2012 Motorcycle(s): 94 EX250, 81 GS450 Posts: 67	But thats the thing, I wouldn't want to increase the rear tire width on the ninja. I love the way it rides. If the bike was putting out 42-50 hp a 140, 150 tire would be welcomed. Truth is any of those changes would hurt the ninja, it'll look cook.

April 13th, 2012, 12:14 PM	#9
extremez31 ninjette.org member Name: Rich Location: New Jersey Join Date: Apr 2012 Motorcycle(s): 94 EX250, 81 GS450 Posts: 67	Thanks for the replies. What tires would you recommend on the pregen 250? I do want to do some trackdays so more emphasis on sport riding. I need some rule books on the fork conversion, this would look pretty but i have a feeling it will put me up against some serious bikes. Dampening should be ok as the bikes are not too far apart in weight. I may just do this...

April 13th, 2012, 05:00 PM	#10
duckracer ninjette.org member Name: Randy Location: Ofallon, Mo Join Date: Dec 2011 Motorcycle(s): Ducati 1098 and 04 Ninja 250 race bikes Posts: 60	I have done this conversion (pic's of Duc-asaki) will be posted in another thread soon. I used a Yamaha R1 front that I had lying around. So, yes the 250 triple clamp stem is press fit, then welded in, but only at the bottom. You grind the weld down and press the stem out. The 636 stem is the same size as the R1 stem. But it is aprox 1/4 inch larger diameter than the 250 stem. So you need to weld up the 250 stem larger than the press fit for the 636 lower clamp, then turn it down to a 1 to 2 thousands interfearence fit. Heat the lower clamp and cool the stem then press them together and your lower is done (you can't weld them as the stem is steel and the clamp aluminium). The upper clamp has a smaller diameter seat so that will need to be milled to provide the correct stack height. That is all the machining you should need. The front tire is now a 120/70. I run a single caliper and have more than enough stopping power. On the rear I am running a 17 inch new gen wheel with a 140 tire. Keep an eye open for the new thread and you will be able to see how I eliminated the rear caliper torgue arm. My rear caliper is mounted with a one off caliper mount/wheel spacer that retains the caliper vie the swing arm top and bottom. The turn in will be just a tad slower with the bigger tires. That is easy to fix by raising the rear or lowering the front. I have my forks set 10mm from the top triple and the turn in now matches my Ducati 1098 race bike. So this is a good conversion, but for most racing orgs it will be illeagle and push you into 250 superbike. Check your rule book. My org's 250 lw gt is a run what you brung 250 only class so mine is accepted

April 16th, 2012, 01:24 PM	#11
gt_turbo ninjette.org sage Name: L Location: WI Join Date: Apr 2011 Motorcycle(s): '09 250R, '13 CBR500R Posts: 709	@duckracer what did you do with the ignition switch? i am working on a 636 front conversion on my 09 250r, the 250 ignition seems too small to fit the 636 triple.

April 16th, 2012, 01:27 PM	#12
extremez31 ninjette.org member Name: Rich Location: New Jersey Join Date: Apr 2012 Motorcycle(s): 94 EX250, 81 GS450 Posts: 67	I think using a 636 ignition and key would be the simplest solution

April 16th, 2012, 05:00 PM	#14
duckracer ninjette.org member Name: Randy Location: Ofallon, Mo Join Date: Dec 2011 Motorcycle(s): Ducati 1098 and 04 Ninja 250 race bikes Posts: 60	Sorry, been busy. I used the stock ignition switch. The R1 top triple just needed to have the ignition switch hole bored out slightly, and I added longer bolts with spacers made from aluminium round stock. After I locktited the bolts I ground the heads to help prevent theft. The cool thing is the steering lock feature still works. Most ignition switches use a standard bolt pattern since the factories usually don't make them, and source them from an outside vendor. Unless you buy a Ducati then like me you are screwed! Damn Italians!!!! The 250 ignition switch has a plastic cover that can be removed and it would probably fit as is, but the plastic cover makes the switch look better. If you don't have access to a mill or lathe you could use and dremel to open the hole.

April 16th, 2012, 05:24 PM	#15
gt_turbo ninjette.org sage Name: L Location: WI Join Date: Apr 2011 Motorcycle(s): '09 250R, '13 CBR500R Posts: 709	I have the opposite problem, the 250r ignition is about a quarter inch too small than the 636 triple. I'll have to find some thing to fill the gap. Rubber gromet maybe. How do you try to retain the stock 250r geometry with the fork conversion? Is it like measuring the fork length from axle to top of the triple tree and trying to keep that distance? Unfortunately I did not measure anything before i dis-assembled.

April 16th, 2012, 07:43 PM	#16
duckracer ninjette.org member Name: Randy Location: Ofallon, Mo Join Date: Dec 2011 Motorcycle(s): Ducati 1098 and 04 Ninja 250 race bikes Posts: 60	The geometry will be way different. You are going to have a lot less fork offset with the 636 front end. This will give you more trail and make the bike hold a line really well. I use rake and trail as well as swingarm angle to set my race bikes up. But you can plan on having around 10 to 15mm of fork above the top triple clamp. This is because you have less fork offsett and the forks will be standing up more straight than stock. Just start at around 10mm and make sure you have front wheel clearence, then raise of lower the forks untill you get the turn in where you like it and gives you good feedback.