Hey guys,

I have an MC21 that has been slightly changed over the years by previous owners and myself. I need some advice with a set up issue.

Firstly, fitted to the bike are '95 ZXR750 forks/triples, running the standard front wheel. The rear is an SP shock with standard SP (red) spring. I have done no valving/rebuilding work, though that is the plan when money permits.

The issue I have is that I believe the front forks as they MAY sit the front end up too high. When static the bike appears to be balanced front and rear, but when loaded and moving it looks (from pictures) like the rear sits too low/or the front is too tall. What I want to determine is whether it is more likely that I have a rear spring issue, or are my forks positioned incorrectly from the get go?

- Forks/triples are 1991-4 ZX7R. They are sitting about 6mm out of the top clamp.
- Rear definately does sag with a rider more than i would like.

Is there some form of basic geometry settings that I can apply to the bike to get a good starting point?

What is the length of the standard 21 forks? If they are longer than the ZXR ones that would indicate the problem is with the rear, yes?


Also, what rear spring options do i have available to harden it up? I hear HRC ones are available, but where do you get them? What about K-Tech?

Oh and yes the forks are designed for a heavier bike and should be resprung. But position in the clamps is something I would like to determine.

Need photos really mate, but its usually the rear spring sagging too much that makes them look nose high in riding pictures.
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Hermit wrote:Need photos really mate, but its usually the rear spring sagging too much that makes them look nose high in riding pictures.

Will get on to better photos, but here is an average one under power down the straight.


Spring options though? Rebuilding the shock is fine but how to up the spring rating?

Mod edit: BB code correction, please check your image codes are correct FY

Actually the fork does look long in that pic. The gap between the front of the lower fairing and the ground seems wide. Also the problem can be exaggerated by having a 120/70 front tyre. A 120/60 would lower the front wheel closer to the floor slightly.

What's your laptime at Ruapuna on the NSR?
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Here are 2 threads that might be of interest to you?

http://www.nsr250.net/forums/viewtopic.php?t=11032

http://www.nsr250.net/forums/viewtopic.php?t=8292

But for what it is worth, the length of an assembled MC18 R5k fork (with no load on it) from the centre of the front axle to the top of the stanchion is about 722mm.
What is this measurement for your forks? Are they '95 ZXR750 or 1991-4 ZX7R?

Also, if you do end up raising the drive sprocket (in relation to the rear axle), it may induce a bit more antisquat.
<edit> Actually, after thinking about that a bit, I think that is wrong. The NSR generally is set up to squat the rear suspension under power. </edit>
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TuckerBag wrote:Here are 2 threads that might be of interest to you?

http://www.nsr250.net/forums/viewtopic.php?t=11032

http://www.nsr250.net/forums/viewtopic.php?t=8292

But for what it is worth, the length of an assembled MC18 R5k fork (with no load on it) from the centre of the front axle to the top of the stanchion is about 722mm.
What is this measurement for your forks? Are they '95 ZXR750 or 1991-4 ZX7R?

Also, if you do end up raising the drive sprocket (in relation to the rear axle), it may induce a bit more antisquat.
<edit> Actually, after thinking about that a bit, I think that is wrong. The NSR generally is set up to squat the rear suspension under power. </edit>

I'll measure mine up tonight. They are 91-94 model forks, and i was pretty sure they were around the 700mm mark. But I may well be wrong. I'd be interested to see if dropping the triple clamps causes the tyre to rub on the plug lead though...

Yes I'm currently running a 120/17 Racetec front. I know it's not ideal but the tyre was free and it handles ok so far.. Have a 110 supercorsa on the way though.

Hermit wrote:Actually the fork does look long in that pic. The gap between the front of the lower fairing and the ground seems wide. Also the problem can be exaggerated by having a 120/70 front tyre. A 120/60 would lower the front wheel closer to the floor slightly.

What's your laptime at Ruapuna on the NSR?

Looks like the ZX7R forks are 29" in length as opposed to 28" as MC21 originals (correct me if that is wrong). So what's the easiest answer? Drop the triples by an inch/25mm or so?

Do the original forks sit flush with the top triple? I can get it close to standard then set sag if I have enough info. Anybody?

Unsure of laptimes, that picture was the first proper Ruapuna outing on that bike, and it was wet. But without a doubt in the low 30s