I have MC18 and the shock is blown, can't ride the bike as is. Finding new one has proven difficult so I'm researching the possibility of a swap from another machine or having a custom shock built, I'm sure Ohlins or Penske can do that.

Question for the experts is what is if any the difference between the MC18 and MC21/28 lower linkages?

I have +/-280mm eye to eye length and according to Ohlins website MC21 and MC 28 are 302mm, so If everything else is the same only thing I will have to do is shorten the shock, or order a CB900F shock which is 283mm for same style shock.

Any help appreciated

D

Have you looked into getting yours rebuilt?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Rebuild stock shock? kinda waste of time, it's an emulsion type (no reservoir) and I don't see the plug for nitrogen fill, so that probably has to be added, loads of work and no gain.

Been doing some looking and '02-'06 CB900F (we call them 919 in US) has same length and mounts, but the spring rate from Ohlins is 1028 lb on CB vs 742 lbs on MC21. If the linkage system is same/similar on MC21 and MC18 I can order the 919 shock re-sprung and re-valved for 742 lbs. Ditch hydraulic pre-load adjuster and save few bucks as well.

Got a 900 Hornet shock from a friend, it's pretty close. Other than spring rate being 30% too much, top mounting bush needs to be drilled for the larger bolt and milled down to narrow it. When I get a chance to play with it I swap the spring for NSR one and try it.

NSR is the dirty one

the CBR600 F4i is also a pretty close match.

Perhaps for MC21, looking at Ohlins site the CBR600 shocks they list are either 295 or 310mm, mine is 280mm

The MC21 has quite a different linkage to the MC18. Check here http://www.nsr250.net/forums/viewtopic.php?t=8292&highlight=

I tried to fit the MC21 Shock to my 18 and it would not go even tho they are not that different in length.

I had it cut down to length and rebuilt by a suspension expert and it seems really good on the road. Not too expensive either from memory about $140 NZ or 70ish pounds

Thanks for the links! I'm relatively new here and missed the thread entirely, good read, CAD file pretty awesome too.

One question to the experts: The HRC plates, anyone tried them? I can easily have them remade and willing to try them once I figure out what I'm doing with a shock, are they designed for a 17" wheel or ...?

I can rebuild the shock (with little assistance) and it would be the easy option, but the Hornet shock I have is on loan as the owner wants back at some point as he intends to keep the Ohlins if he ever sells the bike, so I don't really want to re-valve it and than have to do it again. I would look for another one but those bikes are rare in US.

HRC link plates make the world of difference, and gives the MC18 a much more agressive stance. They also sharpen the steering and increase the rear suspension "rising rate".

Win everywhere!
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Andy.
NSR-WORLD.COM

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I'm off to the laser-cutter with a proper file and the old link for material sample, seems quite a bit different, also I assume the "F" on the drawing is equivalent of "F->" on the link.

I wonder what is that last hole marked up for on the left of the drawing?

Got a 1994 CBR600 shock, $28 shipped, it's nearly identical to MC18 secs, I was using Ohlins specs as a reference, only issue is that CBR has a smaller hole on the top mount and it's too wide, but that's an easy thing to correct, drill the bushing and shave the sides.

Reason I went with '94 is that it was the first year they had remote reservoir and full adjustment, compression and rebound. Spring rate is 50 lbs more than MC21 (I assume MC18 has similar rate?)

Once its rebuilt and modified I will update further. I don't expect a miracle but at low budget solution.

Also I had 6 sets of HRC linkage plates made, will try with it with stock and HRC spec plates.

If anyone else is looking to get some of these bits made, I have supplied cutting files (.dxf files) for download at the bottom of this blog post.

With any luck, you can just email these to your local cutter.
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[color=#808080][size=9]Yes,.. I too know how to waste Time and Money,...

I made my own cut file, traded some shirts for some plates... barter system is awesome!

I'm using OHLINS rear shock, that from 2006 model CBR1000rr. But need to set up the spring for your weight.
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1996 HONDA RS250
1995 MC28 NSR250 SE red/white/green
1994 MC28 NSR250 sp W/ RS250 engine

Ohlins shock spec:

2006 CBR1000RR Length 314mm (+6) Stroke 58mm Spring 685 lbs

NSR MC21/28 Length 302 mm (+6/-6) Stroke 50mm Spring 742 lbs

NSR MC18 (measuring my old shock) Length bout 280 mm, spring ??

So CBR shock is little too long for MC21/28, however taking 8mm out of stroke will get you close (306mm)
it's under-sprung so will need new spring and valving and also it has attached reservoir that might clash with subframe.