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Tech Help 1983 Suzuki XN85D Turbo

This article was written by Steve Klose . (Revised 9/12/01)

Low production numbers and few riders with considerable miles on their XN's odometers make compiling an accurate service history of the Suzuki difficult. The following are my experiences with my 20,000-mile Suzi T along with a few observations from a handful of other XN85 owners.

First and foremost is the propensity for the XN's exhaust system to retain water better than Roseanne Barr. True, water is a by-product of combustion, but it would appear that exhaust system condensation is more of a problem on the XN85 than on any of the other factory Turbos -- or on any other motorcycle for that matter. When I removed the exhaust system of my XN for service after the garage-kept bike had been sitting for about 4 months what must have been more than a cup of water poured out onto the floor! I'm not kidding. And when I removed the cylinder head a small puddle of water was sitting on top of each piston!

Why it collects water at such a prodigious rate is a mystery, but our sources at A.T.C.O. (Antwerp Turbo Cycle Owners) in Belgium report that all the XNs in their organization (less than 10) have rotted pipes.

The first "breakthrough" of rust almost always occurs where the pipe leading from the muffler is joined to the pipe exiting the left side of the turbocharger which happens to be directly under the engine. This also, not surprisingly, is the lowest point of the exhaust system. At startup the exhaust will force the moisture through the rotted-out juncture and a tell-tale puddle of water will collect under the engine. If the hole is small enough it can be welded, but of course that doesn't cure the moisture collection problem. I've been advised to drill a small drain hole through the pipe, but then the water only drains when the engine is running which doesn't help things much if the bike is left idle for extended periods of time. (This abundance of moisture may also explain why my turbocharger wastegate was found rusted shut).

If you'd like to end your XN85 pipe rust problems once and for all, Louis Thompson of England recommends a stainless-steel exhaust system from a company called Gazelle. Their chief technician who goes by the monophthong Brausch (Brausch@gazbike.demon.co.uk) says that a common problem on the XN85's he's seen is a collapsed inner "skin" on the turbocharger intake pipe. This forces the turbocharger to suck air through a hole the diameter of a writing pen. Consequently, the bike feels as if the turbocharger is not working at all. Gazelle can replace the entire exhaust system with their stainless-steel parts for about £600, or about $1,100. Usually the bike must be brought to Gazelle for custom fitting of the pipes, but since Gazelle has done at least two XN85's they've retained a template making custom-fitting unecessary. They can be reached by e-mail (info@gazbike.demon.co.uk). Their web site can be found at www.gazelle.demon.co.uk.

In tearing my XN engine down to the cases I've discovered two interesting things. For no explicable reason the intake valve on the #1 cylinder had a pitted contact surface. All the other valves were fine. The pitting was bad enough that I decided to replace the valve as opposed to having it resurfaced. Note that Suzuki strongly suggest that the valves not be lapped. Just pop in the new valve and move on.

Another discovery is that cylinder base gaskets are no longer available. Fortunately the gasket is steel and the old one can be reused if it is not bent or otherwise damaged. So be particularly careful not to harm the gasket when removing the cylinders. When replacing it sand it lightly with a #400 grit paper and spray it on both sides with a high-heat paint. Silver looks best.

Early '80s Suzuki fours suffer from weak stators. So when my charging system failed at 18,000 miles I immediately suspected the stator. Much to my relief the failure actually occurred in the rectifier, a far less expensive part. You'll need a multimeter to check it along with the service manual but it's only a 10 minute task. At 23,000 miles the stator, as advertised, finally did give up the ghost. Instead of a factory replacement (about $350) I opted for a rebuild from Willie's Cycle Stators, 25921 Highway 280, P.O. Box 10, Camp Hill, AL, 36850 (205-896-4141 or 1-800-334-4045). At first I was told they had a rebuild "on the shelf" for about $160. In light of the extremely low production numbers on the XN85 I doubted this, but bowed to their wisdom. Sure enough the stator they sent to me was a perfect fit - for a GS1000. Unfortunately it was too narrow for an XN and the lead wires were about 14 inches too short. After a short discussion on the phone with Willie's I suggested they rewind my existing XN85 stator core. They agreed and now Willie's has a model for any future XN85 stator rebuilds (if any are ever needed). If you belong to the TMIOA mention it to Willie's for a discount. We do know of another promising source of Turbo stators but you'll have to join the club to find out - sorry, but that's the agreement we have with the manufacturer, who normally does not sell to end users.

XN85s are notoriously hard to shift when the engine is cold. It's far less of an annoyance in the heat of summer than in winter, obviously, but it can still be bothersome nonetheless. Heavier oils don't help it any so stick with the recommended 10W-40. I've never used synthetic oil so don't know if it would improve shifting or not, though I doubt it. Since oil in a turbocharged engine should be changed twice as often as a normally-aspirated engine to ensure long turbocharger bearing life the use of expensive synthetic oil is not cost effective. Still I wonder...

The engine Thermo-Sensor, which detects the change in oil temperature as a change in its resistance, is rather fragile and the sensor "cap" which holds the wire leads can work itself loose from the sensor (located on the left side of the engine under the injectors). Be careful when wrenching around the area.

If you do have the injectors removed for any reason it's a good time to check the o-rings on BOTH side of the injectors. They're easily damaged if not inserted properly. When reassembling keep Chubby Checker in mind and twist - do not push - the injectors back into the delivery pipe and then insert the assembly into the cylinder head. A little WD-40 works wonders here.

Check body panels for tightness at every opportunity. Side panels are especially prone to popping off at speed. Air "scoops" are difficult to remove and can be easily damaged if the job is not done properly. Worse yet, you can crack the fairing. Have patience. Side panels and scoops are still available. The scoops come painted, with the TURBO decal applied and with clearcoat. Side panels come primed, and the paint is no longer available from Suzuki. You'll have to get an aftermarket color-match. Fortunately we have the color code for the paint - 99000-10209-15K. It goes by the name Iron Silver Metallic.

Ramon Becerra of California, who races an XN85, reports that handling can be improved with the use of Kawasaki 900 fork springs. Ramon also installed a Works Performance "Ultra-Sport" shock in the rear and is happy with the change, saying it's much better than stock especially after a "few heated miles."

I like to use two fingers on the front lever when braking, but pinning the remaining fingers to the throttle grip when braking hard is no fun. I've replaced the recommended D.O.T. 4 (glycol-based) front brake fluid with D.O.T. 5 (silicone-based) for less mushiness in the lever. Since then I've been advised against using #5 (causes the caliper seals to swell I'm told). Better to use the new #5.1 fluid which is also glycol-based. Disconnecting the anti-dive and installing braided steel brake lines will improve lever feel even more.

Other parts no longer available include rear sprockets and windscreens. There are places that can custom make the sprocket, so keep your old one as a template. Aftermarket windscreens are available from Gufstafsson Windscreens (904-824-3443) in Florida. Mufflers were reported unobtainable for about half a year in '98. Then a large boat shipment suddenly arrived in the States, and are said to cost a reasonable $150 a piece. Another mystery of the sea.

The only performance mod I know of for the XN85 is an adjustable wastegate regulator available for $90 from Andy Morris of New York (516-728-8961). It installs in about 15 minutes and, after road-test adjustments, lets the turbocharger build boost closer to the 12.5 psi "kill" point determined by the onboard computer. It really works. For the first time I was able to see my boost gauge light up all seven segments after installing the device Andy calls the "secret weapon" (so-called because it hides in the right-side storage compartment). Well worth the asking price. Short of that you can try Ron Graf's Weak Turbo Wastegate Spring fix described in his Honda CX Turbo tech help section. It's a little more trial-and-error, but the results are the same and you get to keep your fairing storage pocket.

There you have it. Not much to be wary of considering this was a one-year only bike (in the States anyway) produced in ridiculously low numbers and that Suzuki does everything short of denying the bike's existence.

Last Modified March 06, 2007, 18:41:38 Eastern Standard Time
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