Installing a ZX750 shock
This is the story of a happy accident. Our man was playing shop-by-picture on eBay and managed to get a ZX750 shock when he thought he was getting one from a ZX600. As it turns out, this shock does work on the EX250, particularly for the waist-unchallenged rider. Small, wiry riders may want to look elsewhere.
It's easy to confuse these two shocks. They look exactly the same; there is no difference in dimensions, hose routing, etc... The only difference is the number on the side. Part number is 45014-1351 from years '87-90. For installation, just follow the article for the ZX600.
The official model name of this bike is the ZX750F1 (1987) - ZX750F4 (1990). The marketing name is Ninja 750R. There was also a ZX750H model that overlapped some of these years, aka Ninja ZX-7. This shock looks like this, and you don't want it:
You want the shock that looks just like the ZX600 shock.
Notes and opinions:
So, I got this thing by mistake. I figured what the hell and changed the oil and put it on my bike to see how it would work. After a short ride a week or so ago, I was pretty pleased with how it felt. Then I took a 125 mile run through some of my favorite twisties. Lots of long sweepers, tight switchbacks, and plenty of rough pavement, with some freeway riding going to and coming from. Overall, I think this shock is perfect for me, at about 250-260 pounds in gear. It did not seem to be too stiff, and it definitely performed better than my old EX500 shock. With the EX500 shock set for me (cranked about 2/3 - 3/4 of the way down) the ride was stiff enough, but tended to be harsh on particularly bumpy roads.
Tearing through the twisties the back end felt planted, and the bike felt more balanced front to rear. I was being particularly harsh in my riding style, so I think it's fair to say that you can definitely use a shock from a ZX750, but you should be at the "heavy" end of the spectrum. My buddy who sometimes gets to ride my 250 only weighs about 170-ish, and he barely compressed the shock when he sat on it. The EX500 shock at about 1/4 preload fit him fine.
Final verdict - this ranks as one of those things where sure, it'll work. But there are a couple of reasons NOT to go this route:
1. EX500 shocks are cheaper (usually) and fit a broader range of riders - all you "average" height and weight people.
2. ZX600 shocks fit a broader range of people slightly heavier than "average", but not in the 225+ range.
3. Depending on what you need in suspension, you might be better off with an aftermarket shock specifically suited to your weight and riding style.
2000 mile update
This shock is definitely NOT for light riders. I use this bike to commute daily and the shock is actually pretty "tame" on the streets during normal commuting. I weigh about 250 geared up; a 175-pound friend finds it a little harsh for him. The bike definitely sits lower than it did with the EX500 shock, but I also had the preload on the 500 cranked about 2/3 or more of the way. I never got around to adding any air or changing any of the settings from base other than the oil swap.
I've now taken it out into the canyons in several different conditions, from smooth, freshly-paved 2 lanes to older, less well maintained (read: bumpy as hell) 2 lanes. For riding in the twisties, you get a lot more feedback from the rear end, and it seems to get stiffer as you hit more bumps in quick succession. It never gets out of shape for me, and I have yet to bottom it out. Overall, I am pleased that my "lemonade" turned out as well as it did, and I would definitely recommend this as an upgrade for riders in my weight range who don't have the $$ to spring (pardon the pun) for an aftermarket shock.