Hi, I'd like to share with anyone here who would like to upgrade their rear suspension, a very good change over at very little cost. Now to start with, if you want to bolt something straight in , well this is not the way for you, it requires a bit of basic metal work and some ingenuity. This is not saying it's a hard job to do, and you do have to spend some money and lose the resale of your original shock as a complete unit, as you have to use components off your MC18 showa.
I have photos to put up, if I can upload them but first I'll describe what and how:
No way can I fund a new Ohlins, and seconds are hard to find, so I searched the net for something similar, mainly with compression and rebound adjustment, I have used a YZF R6 2010 rear shock in another NSR chassis that worked well and was reasonably easy to fit up, so I wasn't going in blind. here wasn't much in the way of modern units that came within the spec I was looking for until I cam across a SACHS , out of an MV Augusta F4 750. It had rebound and compression adj, eye to eye was within 4mm and the spring diameter's, Id & Od where the same as my NSR's. Better still the price was right, 103.5 pound.
BTW, these are the same shock as used on most high spec Ducati's as well, and there are a heap of them on offer in the US on theBay, possibly they have been replaced with Ohlins is my Guess, and again, at very reasonable prices.
So here's what the go to fit one up: Firstly remove your NSR shock and undo the lower shock eye from the from the shock rod. This requires the spring to be compressed and a spanner put on the lock nut. Another method is to grind of the anchor pins that hold on the preload adjuster sleeve and slip the adjusters and sleeve off over the top shock eye. Rules out using the shock again thou. From your original shock you will need to use the lower spring guide/retainer and the retaining plate that sits underneath the guide, and the spring. Do the same with the sachs, remove the lower spring retainer and the spring.
This is where it gets a bit tricky, from the Sachs shock, you take the top eye retaining washers out, they are machined with a step and a giude on them and you have to cut the guide of at the step( hacksaw does it) this is so you can get the NSR 12mm shock bolt through the sachs to eye, as the sach are 10mm both ends. Fortunately the sachs top shock eye bearing has an ID of12mm so its a then a straight fit, once the 10mm guides are cut off.
The bottoms a bit easier in the bolt up as it matches the 10mm NSR lower eye, but you have to make up a couple of spacer to take up the gap left by the narrower sachs unit, you will need 2 spacer with a 10mm id hole with approx a 22mm od. The spacers should be approx 6mm wide.
The next tricky bit is to linish or file the sachs lower shock eye Aluminium casting outer face "flat", as it's cast with a radius and this radius contacts the suspension "dogbone", so by removing some of the radius you gain a bit more clearance, without doing any damage to the shock, the shock need only clear the dogbone by a 1/2 mm as all the work from there by the shock is up away from the dogbone.
The next bit of work needed is to fit the NSR spring which slides straight on to the top perload adjusters then slip the NSR lower spring guide oner the bottom of the shock and into place. The NSR lower spring retainer the will need to have a slot cut into it from the outside to the centre, just slightly wider than the sachs shock rod. Then th3e lower retainer has to have the Id increase to the dimensions of the sachs lower retainer/ rebound adjuster, at the worst this can be done with a set of files or a die grinder, then once with a comfortable fit, slide the NSR lower retainer into the spring guide and over the sachs retainer and bingo, you have a working modern rear shock that fits your MC18.
Whilst we where doing this we checked the valveing of the sachs against that of the NSR and the sachs range of adjustments places the stock NSR valveing at about a a third of the way through the sachs adjustments so there is plenty to play with. Proof will be in the running, and that's a way of at present but we are confident from previous experience that it will work fine, particularly seeing we are sticking with the original spring and the bike has had a bit of weight taken out of it already.. The spring when installed has no load on it al all and is loose in the guides so it's all good. The picture are a breif look at some of the installation work, hope they explain a bit better than this post.
Thanks Andy, yes should be a good thing for the early bikes, even when the SP & SE loose their damping or are just plain worn out. The ducati shock has one advantage over the MV unit, in that the rebound can be adjusted with a skrewdriver, as a against the sachs where you have to get under the bike with your hand to twist the knob.
With your permission Jeff, I'd like to add that to the main site sometime. Maybe in the Tech section, and link to it from within the "suspension tuning" page.
Update us when you know how the bike rides, please. _________________ Andy.
NSR-WORLD.COM
Please keep all responses to Forum posts on the Forum so that others may benefit.
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No problems there Andy, That is what I put it up for, to share the info and possibly help out someone who is looking to update or repair. I hope it gets at least one NSR rider out of trouble.
The ducati's are a little different in that the can positioning is vertical, but the same shock, and these are just some of the series and years that are available. They range in price, in USD from $50.00 to $100.00.
I have few Ducati shocks laying around (900 SS, 996 S and 1198 S) none will work as the reservoir is positioned differently and interferes with the frame or some other issue, I already tried....
What seems to be best fit for MC18 is the 1994 CBR 600 F2, it's a one year only here in US as '93 has non-servicable shock and '95 has a different dimensions. '94 However has remote reservoir, adjustable compression and rebound and spring rate is almost same as MC18 (little higher which is actually better considering I'm a bit larger than typical Japanese teenager the NSR was intended for) The only mod you have to do is top mount has to be shaved from 27mm wide to 25mm and drilled from 10 to 12mm
By the way, every 748-916-996-998 bike has the same spec shock, only difference is the spring rate, more spring for 2 passenger.
Sachs came on entry level bikes, Showa mid-level and Ohlins top shelf
OK, here are some pics to illustrate
900SS shock with clearance issues
916 style shock (this one from 996)
and here is the problem with 848-1098-1198 style damper, wheel adjusted all the way back. This is an 18" wheel, I don't have a 17 to check clearance.
Another problem is that NSR linkage ratio is much lower than Ducati so NSR uses roughly 750 pond spring while Ducati is in 450 pond category which is a significant difference requiring complete re-valving
I keep coming back to this 1198 shock that I have, It's an Ohlins and I'm eager to make it work.
I measured a spring rate on my MC18 and it's about 12.5KG/mm, according to the markings the one on the 1198 shock is 8.15KG/mm (457 lbs)
length is pretty close, about 290mm eye to eye. Wonder how much clearance I gain with 17", in theory should be 12mm which might be enough, however if the tire meets the shock at speed results may be catastrophic so I have to make sure there is no chance of interference, perhaps shorten the reservoir? I have an extra one that was damaged, perhaps I can experiment or convert to remote reservoir but then it becomes too much of a project.
I see that the problem is that the MC18 RK5/6 has a different rear calliper restraining setup than my earlier MC18 chassis, where my rear brake dose not have the floating rear torque arm on top of the swing arm, which certainly restricts the amount of room you have to swing the canister around. You might be able to add some material into the torque arm so that it gives clearance, this wont effect 'how the rear brake works, asd it's over engineered as is and not a motocrosser. Other than that weld a anchor point onto the swing arm and shorten the torque rod and fix it to the anchor point, this also won't hurt your rear braking as the 21's ended up back with the fixed/slide method as on the earlier MC18's. I do not like the cannister barely missing the rear wheel bit, forget that one. Grab a MV unit, their cheaper than most but superior to the showa that comes standard in an MC18, yes we'd all like an Ohlins, Fleabay @$1,375.00 aussie dollars..Not.
Sorry I thought you just could not get the can around square. The attached photo is off a MC18RK5 chassis with a 2010 YZF 600 rear shock, some other things are none NSR as well.
Pretty sure I posted this somewhere else here but figured it's a good thread to add shock info:
IIRC MC18 shock was 285MM, and I measured 12.5 KG spring
First I was doing a conversion with 1994 CBR600 shock which is about same length and slightly over 13KG spring but it was blown and I gave up after I added cost of parts needed to service it
That's when I looked in to later CBR's
'95-'96 is 289mm while '97-'98 is 287mm so I picked one up from a '98 bike for $50
Used belt sander to shave down top bushing from 28 to 24.5mm and drilled the eye from 10 to 12mm, easy job, total cost $50 and no need for spring swap
Ran remote reservoir hose towards the back and tucked it under back seat
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