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Author Topic: RD350 TO NINJA 250 SUSPENSION SWAP  (Read 4125 times)

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Offline banzairx7

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RD350 TO NINJA 250 SUSPENSION SWAP
« on: September 07, 2013, 01:44:07 PM »
I recently purchased a 74 RD350 and am starting down the modding road. The first thing I'm doing is swapping the suspension/brakes completely over to Ninja 250 bits. I picked up a wrecked 08 Ninja off craigslist as my parts donor. I've seen a few of these swaps but didn't see the details that would make it so I could repeat it easily. I figured I'd try to document my attempt here for others to use.

Today was fitting up the front forks. I ending up using two Ninja 250 All Balls bearing kits to get something that worked. I used the two upper races from the Ninja kit for both the upper lower races in the RD. These are the smaller of the two races. The old races popped right out and I put in the new ones. Then I had to use the two lower bearings again both top and bottom. The lower bearings from the Ninja are a little taller than the uppers. This allows you to catch the upper area of the stem where the bearing needs to ride. If you use the shorter bearings the upper bearing will sit on the turned down part of the Ninja stem and flop around.

Finally I still needed a spacer to make up the gap on the top. The Ninja stem is a little longer than the RD one. Here is a drawing for part I made-


And some pictures of everything bolted up-





Over this next week I'm going to start on the rear suspension. The plan is to use the complete Ninja rear including the mono shock.
« Last Edit: September 07, 2013, 01:45:30 PM by banzairx7 »
1974 Yamaha RD350
2006 Derbi GPR125, EFI'd and thoroughly modded
2003 Derbi GP1 Scooter, 70cc's of fury

Offline banzairx7

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #1 on: September 15, 2013, 03:23:08 PM »
I've gotten a lot done over the last week. The rear suspension is mounted up minus the upper shock mount. That should be done this week though. Here is the run down of what was done-

The swingarm and swingarm spacer needed to be reduced in width. I machin dthe swingarm in a milling machine and shortened the spacer using the Lathe. The bearings in the swingarm pivot need to be tapped in as far as they will go too. Lucky for me that there was room to move them in which made life way easier. The Ninja swing arm bolt fits but it is short by ~1/4".













I was able to use the center stand mount for the shock lower link. The center stand mount was within 1/16" of the Ninja lower mount. All that was needed was some spacers. The bolt shown in the pictures is just for scale. I did have to source a 140mm long 12mm bolt for the lower link mount. I'm still waiting for it to show up.











And finally some pictures of the bike as it sits right now-





1974 Yamaha RD350
2006 Derbi GPR125, EFI'd and thoroughly modded
2003 Derbi GP1 Scooter, 70cc's of fury

Offline Vintage Smoke

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #2 on: September 15, 2013, 04:26:50 PM »
Looks awesome!! Really nice work!!
BTW....tons of people mod and race the 250 Ninjas. Check out www.Ninjette.org. You will find a bunch of good info on upgrading the 250 suspension and brakes as well.
Nick Pastore
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www.VintageSmoke.com
77 RD400
73 & 75 RD350
75 RD200
2010 Ninja 350R (Banshee powered Ninja!!)

Offline clem73

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #3 on: September 16, 2013, 03:28:37 AM »
I did a similar mod on my DS7. I used ZX6E front end, ex250(2008) wheels, swingarm, brakes and GSXR600 rear shock. I didn't use the centerstand mounts since it appeared to give the linkage too steep of an angle. I tried to replicate what was done on the ninja as good as I could. Some problems that I ran into are the sprockets of course don't line up and most exhaust won't fit with the linkage installed. The rear drive hub will need to be turned down for the chain to clear the frame well enough to be safe. Looks good so far, keep at it.

Offline banzairx7

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #4 on: September 16, 2013, 07:03:50 AM »
Thanks for the pointers clem. It will be a few more weeks before I get to the sprockets. I'm in the process of rebuilding the motor now also. It will be a bit before it's back together.

As far as the linkage location goes I had the Ninja frame and used threaded rod to transfer the suspension mount points over to the RD. The lower link mount on the ninja was ~1/16" lower than the center stand mount.

1974 Yamaha RD350
2006 Derbi GPR125, EFI'd and thoroughly modded
2003 Derbi GP1 Scooter, 70cc's of fury

Offline rdshaw400

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #5 on: September 16, 2013, 07:39:43 AM »
the sprocket issue is super simple, just use ninja sprocket.
I have built 10s of these and found that cutting and welding the triple bolt gives you the perfect amount of space to mount clip-ons above the tree.
the second picture is my bolt on swap incase you wanted to be less weld happy on the frame. although I usually use 2" square stock and cut a 1"slot to slide over the frame and sneak over towards center , then down to the center stand mount .
Mark was sure the bolt on was going to break the motor mount but with more than 1000 bone jarring,  chicago pot hole miles the bolt on works fine other than the crude miscalculated fabrication techniques used on this prototype .

Offline rdshaw400

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #6 on: September 16, 2013, 07:50:36 AM »
if you use the ninja rearsets I find it makes things the most straight forward and cost effective.
you will be astounded with the transformation. I am sure you are already realising how simple this build can be, and all the issues it addresses! good luck it is going to be a great bike. 
your top spacer is perfect.
what is the distance from  center of the old shock mount to the top of the swing arm?
« Last Edit: September 16, 2013, 08:04:12 AM by rdshaw400 »

Offline banzairx7

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #7 on: September 16, 2013, 07:58:34 AM »
I've really been amazed at almost how easy this has been. This is my first go at building something like this. I thought I might have been over my head but it's been coming out really well I think.

The plan was to use 250 rear sets. I'll be getting some aftermarket ones. I only have the right side from my parts bike. For some reason people think the left one is gold. It's not much more for brand new ones.

Thanks for chiming in BTW. It was seeing your bikes online that gave me confidence to go ahead with this.
« Last Edit: September 16, 2013, 03:07:04 PM by banzairx7 »
1974 Yamaha RD350
2006 Derbi GPR125, EFI'd and thoroughly modded
2003 Derbi GP1 Scooter, 70cc's of fury

Offline twinlinemoto

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #8 on: September 16, 2013, 11:15:16 AM »
This is really cool!
1974 Honda CB125S cafe
1975 Yamaha RD350B TZ replica
1968 Honda CB160 racer
1970 Honda Trail 70
1970 Yamaha DT1
1984 Suzuki RM500

Offline clem73

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #9 on: September 16, 2013, 12:15:39 PM »
This is mine so far. Pretty similar to yours

Offline banzairx7

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #10 on: September 16, 2013, 03:07:58 PM »
Glad to see the interest in this. Hopefully this will be a good resource for others going down the same road.

Clem- Digging the gold wheels. Gives the bike a more classic look over the black ones I have.
1974 Yamaha RD350
2006 Derbi GPR125, EFI'd and thoroughly modded
2003 Derbi GP1 Scooter, 70cc's of fury

Offline JA-Moo

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #11 on: September 16, 2013, 10:07:23 PM »
Just wondering, what is the wheelbase ending up with this mod?  :umm:
Just because you almost won once at Operation, doesn't qualify you to do actual surgery..........

Offline clem73

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #12 on: September 17, 2013, 05:26:02 AM »
the sprocket issue is super simple, just use ninja sprocket.

Rdshaw, Maybe the 250 DS7 is different but mine is +10mm off and lining up on the rear sprocket, the chain will rub the frame. My rear drive hub will need to be turned down to clear the frame with no chance of chain rub. Maybe there is a difference between the newer and pre-gen EX250's? I didn't get to take very accurate measurements on the alignment yet besides eyeballing with the straightedge that I use to build guitar necks, so I trust it's straight.

Offline rdshaw400

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #13 on: September 17, 2013, 07:02:17 AM »
Clem,how much did you trim off both sides of you pivot?...I have used R5 frames and no such problems. I am speaking in gen1 terms.
my gen2 suspension bike is storage, but I dont remember anything being quite that far out.

Offline banzairx7

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Re: RD350 TO NINJA 250 SUSPENSION SWAP
« Reply #14 on: September 17, 2013, 07:42:17 AM »
Just wondering, what is the wheelbase ending up with this mod?  :umm:

As mine sits right now 57.5"
1974 Yamaha RD350
2006 Derbi GPR125, EFI'd and thoroughly modded
2003 Derbi GP1 Scooter, 70cc's of fury