What to look out for...
Owners and mechanics highlight the weak spots
1
Normally incredibly tough but they don’t like neglect and long periods of disuse, especially if left parked on the sidestand. The oil drains away from the right-hand ends of the cams, which wear on startup. In extreme cases they rust, pitting the cam lobes and leading first to rattles, then expensive bills.
Happily, most ZRX owners look after their bikes and top-end rattles are more likely down to valve clearances and/or a carb imbalance. Some recommend a manual camchain tensioner (noise increases ‘til the automatic one lurches to the next notch). The ZZ-R1100 engine on which this is based has a history of number three big-end failing, allowing the conrod to exit via the crankcases often related to falling over with the engine running, causing oil starvation. Be wary of a rumbly bottom end and check the oil light goes out quickly.
Clattery noises while the starter motor’s engaged can be a flapping starter chain - the automatic tensioner can fail. It’s easily replaced, or there’s a DIY fix to make a simple manual one.
2
COOLING As mileages rise on older REXS, expect to see more instances of water pump and head-gasket failure, as well as steel coolant pipes rusting from the inside, common on the ZZ-R. Check the carb-heating water circuit - it can get clogged up, causing problems with carb icing and poor running. There’s a filter that should be cleaned regularly.
3
GEARBOX/CLUTCH The gearbox is fine (abuse apart) at normal mileages. If it’s abused or at high mileages (80k plus) the gear selector forks tend to wear or distort, causing it to jump out of gear. Check each gear engages and throttle on and off hard a few times in each gear to make sure it doesn’t pop out. Check the clutch basket - it’s not uncommon for the plates to fret against the basket and shed swarf into the oil.
4
ELECTRICS There’s no fundamental problem here but they’re getting to an age now when problems with corroded, loose or damaged connectors and tarnished (high-resistance) wires can occur. A weekend cleaning, tightening and protecting connectors and earth points is time well spent. Look for evidence of overheating and burning on the main connectors to the regulator and alternator - if in doubt, replace them and splice in new wire if it’s
tarnished. A popular tweak is to disconnect the plug to the K-TRIC throttle-position sensor on the carbs. That means instead of emissions/ noise-friendly mild ignition advance at smaller throttle openings, it reverts to a more extreme advance curve, offering better throttle response - though you’ll probably need to use super unleaded to notice the difference.
5
SUSPENSION Soft as standard, but can easily be stiffened up if desired. The rear shocks are high quality, but as new suffered from poor-quality oil, and often not enough of it, resulting in a tendency to wallow. It’s possible to strip and rebuild them yourself with fresh oil, though they will need recharging with nitrogen afterwards (there is a lot of info on this on the excellent forum at zrxocboard.com). Might be better to trust them to a specialist who can also transform the damping characteristics. Same goes for the forks, which lack rebound damping in particular. There are bolt-in kits (from Racetech notably) which make a big difference, but a good specialist can achieve as much by modifying what’s already there. Try mctsuspension.co.uk or twsuspensiontech.co.uk. For a free tweak to quicken your steering, rotate the chain adjuster eccentrics a full 180° for an extra inch of rear ride height.
6
GREASE (IS THE WORD) The lower the mileage, the more likely that the steering head bearings and swingarms will be running in their original grease. Since they were woefully under-lubed at the factory, you need to remedy that ASAP. The swingarm pivots in particular are prone to water ingress, leading to corroded roller bearings - the roller breaks up and can damage the swingarm itself.
7
BRAKES Those monster Tokico six-pots were big news when they first appeared in the ’90s, but were never as good as they looked. They don’t offer better performance than good fourpots and the extra complication of keeping them in good condition (they’re prone to sticking pistons and corrosion) means many people upgrade to Nissin four-pots from early 2000s Suzukis. You do need to match the master cylinder to suit though, or you may get a hard feel at the lever and no power. The standard pads on the ZRX are pretty soft, which is good for feel but not so good for outright power. Many owners recommend upgrading to HH compound pads, regardless of whether you stick with standard calipers or change them.
8
KEYS There’s a built-in immobiliser, linked to a transponder in the key and a receiver in the ignition barrel. New bikes were supplied with two normal and one red key which allows you to code new keys. Lose the red key and you’re in trouble, so make sure any used bike you look at has all three keys.
“Normally incredibly tough, but they don’t like neglect”