Faults:

I've owned four Yamaha XJ motorcycles. All these 4-cylinder XJs (550, 650, 750, 1100) are cursed with the YICS system that often produces troublesome vacuum leaks.

Subsequently it's common for old XJs to run poorly and defy efforts to tune them. As a result these XJs are often parked, unused and sold, very cheap. Fortunately a repair is straightforward, but few people understand how.

The YICS is simply a narrow passage drilled through the cylinder block. There are four short passages that pass through the cylinder head gasket to each intake port in the head. It's intended to equalize vacuum signals for the 4 carburetors, increasing power slightly.

Vacuum leaks around the head gasket are common and cause all the poor running. The solution is to replace the gasket AND the 4 tiny O-rings at each of the 4 passages.

I did this, and sealed up the 4 passages entirely, using simple 5/16 inch plugs made from steel rod, sealed with Loctite. I lost about 3 horsepower, but the bike runs better and is easier to tune and synchronize carburetors.

Another troublesome issue is counterfeit carburetor rebuild kits from Amazon. I ordered 2 sets, both were incorrectly designed in 2 ways:

1. The float bowl gaskets were cut from a vinyl material which shrank from gasoline, causing leaks and flooding gas from stuck carburetor floats.

2. The float needles had incorrect damper springs. They'd occasionally get stuck closed, causing an engine miss. This defect was difficult to detect. So.... get carburetor parts from a reliable supplier, like XJMike, and not Amazon or Ebay.

Some parts for this bike are impossible to find new, like the carb vacuum diaphragms. Sometimes you have to be creative in finding parts.

Spark plugs... when buying new plugs look for the NON-resistor variant of the correct plugs. They tend to be more difficult to find, but are correct. The stock spark plug boots have resistors in them already so non resistor plugs work best.

Finally, the stock mufflers rusted off, the previous owner installed new mufflers to the original exhaust, they look good and work well, but I don't know where they're from.

General Comments:

These are great bikes. As noted above, the Yamaha XJs are the cheapest street bikes available in Ontario, where I live. As noted above, IMHO it's because of a design flaw that causes vacuum leaks and poor running. People can't always fix them so they're a bargain.

These XJ engines are very compact and narrow for an inline 4, due to a compact design. This makes the bike easier to handle, and it has plenty of cornering clearance.

These engines are beautiful when you finally get everything set up right. Like any 4 cyl 4 carburetor bike, a bit of skill is required to tune and adjust them right. But it's an old school sports bike engine... powerful (for its displacement), responsive, very smooth and free revving. It's happy to putter at low rpm, then instantly wind out to 9500 rpm and 73 hp.

Although this bike is an early cruiser style, the whole bike feels light, compact and vintage-sporty. Handling is fast and responsive, and with the sporty engine, the riding experience is more sporting than cruising. Compared to a modern cruiser, it feels a bit small, almost like a mini bike. But that makes it easy and a pleasure to ride. But tall people, over 6 ft will feel a bit cramped, especially with the stepped seat. A friend had a custom, flatter seat made for his XJ that allows taller people to slide back more, for comfort.

The transmission is slightly clunky at times, but OK. It's a 5 speed with short gearing. 1st gear is very low and great for very slow city traffic.

All gears are quite low. It's geared for the engine to rev high for maximum acceleration.

And yes, it's quite fast. Like many old Japanese bikes, they got a lot of power from a modest displacement. This bike turned the quarter mile in about 12 seconds flat and will out accelerate many modern, larger cruisers. Yet you pay little-bike insurance.

Unfortunately at highway speeds the engine is revving higher than most street bikes.

The suspension is remarkably smooth and absorbent for an older twin shock style. It's air adjustable and can be tuned.

It's a short, lighter bike, so it's a bit of forward-aft rocking over some bumps, compared to modern, long cruisers. But it's okay. Seat height and center of gravity are nice and low.

This bike has shaft drive, which works well, much preferred to a chain. Brakes are fair. They're adequate. The rear drum is good the front dual disc requires a hearty squeeze. I installed new pads, but the brakes will work better if I machine the rotors.

This bike is a rare (one-year-only ) model, all black with gold aluminum wheels and trim. Very retro -80s. But mechanically it's identical to the standard shiny silver/chrome model made for several years in the early 1980s. I like the classic looks.... round lights, 4 exhaust pipes, nice curves and a very purposeful engine filling the frame.

Overall, a great bike with many functional advantages. Relatively light, compact, reasonably fast, good handling, easy to ride, and cheap, cheap. Also it's easy to work on, it's mechanically sophisticated, but straightforward.

Downside is, some parts are tricky to get, it's old and unfashionable, if that's important to you. ..... it looks vaguely cruiser-like but runs like a 70s sport bike. That's a good thing in my book, but definitely not for everyone.

It's got that vintage Japanese bike charm in spades.