Service

SERVICE

Paul Dean

The cam-chain caper

I own a 1985 Kawasaki 900 Ninja that has about 40,000 miles on the odometer. While I have maintained it immaculately, it needs a new cam chain. My Kawasaki dealer tells me it will be necessary to drop the engine and split the cases, despite the chain being mounted on the left side of the engine. This sounds very expensive. Are there any cheaper alternatives, such as an aftermarket chain that uses a masterlink? Eric Black

Tempe, Arizona

You indeed can replace the cam chain without dropping the engine and splitting the cases. First, take off the cam cover and remove the metal camchain guide that bolts between the two camshaft sprockets. Slip a long piece of safety wire around the cam chain at any convenient location, then take off both of the cam sprockets. Removing the sprockets allows plenty of slack in the chain, and the safety wire prevents the chain from accidentally falling down into the cam-chain tunnel. Next, after undoing the ignition cover on the left side of the engine, take the ignition rotor off the end of the crankshaft and remove the cam-chain tensioner that

bolts to the cases just to the right of the rear ignition pickup. Now you can take the cam chain off the engine sprocket, slip it around the end of the crankshaft, and pull it up and out of the engine through the cam-chain tunnel.

To install the new chain, essentially reverse this procedure. Put the safety wire around the chain before feeding it down through the tunnel, then loop the chain around the engine sprocket.

You 'll have to retime both cams, of course, and set the ignition, as well, but this method still is a whole lot easier-and considerably less expensive—than removing the engine and splitting the cases.

No company I know of sells a cam chain with a clip-secured masterlink to fit the 900 Ninja engine. Some bikes do come from the factory equipped with chains that have clipless masterlinks that require their pins to be peened over after installation. Most race mechanics tend to shun these kinds of chains, however, preferring the security of an endless chain to the possibility of a masterlink flying off at high rpm and causing severe damage to the engine—or perhaps even to the rider, should the failure result in a rear-wheel lockup that causes a crash.

Boxer revival

I have just purchased a 1976 BMW R75/6, a 750cc Boxer Twin. It has been in storage since 1988. Please advise me what I have to do to get it back in running condition.

David Morton Kobel Hillsboro, Oregon

That’s a very difficult question to answer correctly without being able to see the bike or knowing more about its present condition. When a motorcycle is stored for an extended period, the amount of work required to put it back in service depends almost entirely on how well it was readied for storage. If it was thoughtfully and expertly prepared, you could have it back on the road in a few hours or less. If someone just walked away from the bike and let it sit in the damp climate of Oregon for more than five years, practically every moving part might need some kind of reconditioning.

There are a few areas, however, that are likely to need attention no matter how capably the bike was stored. You should change the engine oil and the air filter, and inspect the fuel tank for rust and other forms of corrosion. If you find either, you ’ll probably have to treat the tank with a rust-removing solvent and coat it with a good fueltank sealer. The carburetors may have gotten gummed up with the residue evaporated gasoline, so remove the carbs and pull the float bowls for inspection. Clean any residue or sediment that you find in the bowls, and carefully check all the jets and passages for clogging. Blow them out with compressed air if necessary, and use individual strands from a piece of electrical wire to clean any clogged jets. If that tactic fails, simply replace the affected jets; they re cheap.

Carefully check the tires for dry rot before airing them up to the prescribed pressure; actually, you should consider replacing them in any event, since they surely have hardened, even if they haven’t gotten terminally weather-checked over the years. Check the brake-fluid level, and if there is any rust on the brake rotors, use steel wool to clean it off.

I also advise that you remove both cylinders-an easy job on a BMW Boxer-and check the bores for rust, particularly where the piston rings have been resting for years. If you detect any kind of corrosion, hone the cylinders and replace all the rings. Finally, cross your fingers and hope that when you fire up the engine and take the bike for its first ride, no other major problems will emerge to spoil the enjoyment of your new toy.

O-rings or no rings

There is a good chance that the flooding problem with Arthur DeJaeger’s carburetors (Service, August, 1993) is not with the fuel pump but with the float-needle seats in the carburetors. The needle seats on many late-model machines do not thread up into the carb bodies but instead are simply a press-fit sealed with an O-ring in a groove machined around the outside of the seat. The Oring performs the same function as a gasket on carbs that use threaded needle seats. If these O-rings deteriorate, which they sometimes do, gasoline can pass around the outside of the seat body and into the float bowl, even when the float needle itself has shut off the flow of fuel.

I experienced this on a brand-new motorcycle that had two gas-fouled sparkplugs when I picked it up from the dealer. After numerous failed attempts to stop the flooding using other techniques, I pulled the carbs and ultimately found this condition. I finally cured the problem by installing slightly fatter O-rings I found at a > good auto-parts store. I chose not to use the original-equipment O-rings because they obviously were not getting the job done. J.REwing

Lafayette, Indiana

A bum steer

I have a 1982 Yamaha Vision 550 that was involved in a small accident. The only damage was a bent front fork and a cracked rear wheel. I have come across a 16-inch rear wheel from a Maxim and some front forks from other Yamahas that will fit in the Vision’s triple-clamps. My questions are: What are the pros and cons of replacing the 110/90-18 rear tire and wheel with either a 130/90-16 or 140/90-16? And what are the side effects of replacing the stock trailingaxle fork legs with conventional, straight-axle legs while retaining the stock, 18-inch front wheel? I do some mild canyon strafing on weekends.

Albert Cardona El Monte, California

The stock, 110/90-18 rear tire on your Vision has approximately the same outside diameter as a 140/90-16 rear, so the overall gearing and rear ride height will be essentially unaffected by your proposed change. And the Vision ’s swingarm is wide enough to accept the 140/90-16-inch tire you have in mind, which is about 30mm wider. So, aside from a slightly larger footprint, the only positive difference will be visual, while the only significant negative effect will be an increase in unsprung weight that will result in a marginally harsher ride at the rear and a slightly greater tendency to chatter over choppy bumps.

You should not, however, replace the Vision ’s trailing-axle fork legs with inline-axle legs if you intend to keep the stock triple clamps. Even if the replacement legs are about the same length as the originals-which would let your Vision retain its original front ride height-the forward relocation of the axle would reduce the amount of front-wheel trail by about an inch-anda-quarter, from just under 4.6 inches to somewhere around 3.3 inches. The end result would be steering that is spooky at worst and twitchy at best. Instead, either use stock fork legs or replace the entire fork assembly, including the triple-clamps, with one that will provide much more sensible steering geometry. ^