Transformation your YAMAHA XS5650 to a XS BOBBER!

The YAMAHA XS650 was launched in 1968 it had one of the most advanced engines in its class of large parallel twin motorcycles. Over a quarter million XS650s in 40 different variations were produced by Yamaha between 1970 and 1985. The XS650 big twin, in America and worldwide has developed a cult following for good reason. The bike makes a cool XS650 Chopper. The engine and gearbox are unit construction with the crankcase split horizontally for ease of assembly whereas almost all contemporaries in its class in 1968 are either unit construction with a vertically-split crankcase or pre-unit construction with separate engine and gearbox.However, like its contemporaries in its class the XS 650 has a 360° crank angle. This provides an even firing interval between the two cylinders, but also generates some vibration caused by the two pistons rising and falling together. At the heart of the XS650 is a indestructible engine. The best parallel twin ever built.. Tough durability, classic look and abundance of cheap parts make the XS650 the perfect platform to build a KILLER Chopper.

Before you get started in your transformation your YAMAHA XS5650 to a XS BOBBER you will need to diagnose any problems with getting the bike to start.

1. First charge your battery to at least 12.5-12.7V. The XS uses a 12 Volt / 6 cell battery. The type is 12N14-3A. Metric size is 130×85 Millimeter and 160 mm high. The original type is a lead battery with liquid electrolyte. The electrolyte is dilated sulfuric acid with 1.28 density. Safety goggles are a must if you do anything else except disconnecting the battery or charging it!It is most important to keep the acid level between the marks. If it goes below the lower mark the lead electrode (board) of the cell gets exposed. If a section of lead gets dry it will not recover even when the cell is filled up again. Is important to get your battery in good condition so you’re XS BOBBER has juice to run. By oxidation it will be then a partially working cell. The electrolyte level will get lower by evaporation. It is only the water what evaporates, the amount of acid will be constant. A battery never gets refilled with acid. An exception is if you spill the acid – then it has to be replaced of course.The electrolyte is diluted sulfuric acid with a density of 1.28. Before you handle the battery be sure to have a water tap or at least a filled bucket nearby! Refilling requires distilled water.A water tap in a workshop should have a piece of rubber hose attached to it. In case of an accident you will be able to flush the eyes or body parts with the hose! Batteries and bottles with acid must be kept away from children – such things are highly interesting for ‘experiments’!Charging a battery causes combustible gas to escape! Only in ventilated areas! It’s sold at the supermarkets for ironing and of course at service stations. Don’t use ordinary tap water or bottled water since it contains minerals. Minerals disturb the chemical balance of the electrolyte and weaken or damage the battery. A good idea is to get a syringe from the pharmacy to refill the cells. Examine the cables of the battery and the ground connection to the frame! It is a common source of trouble. Check the insulation. The connectors may oxalate – keep them clean and apply some petroleum jelly to keep them protected. You can use a wire brush or same paper to clean the terminals.

In case of an accident you flush with lots of water. Acid starts its destructive work after some delay – it may not even itch at the first contact! Consult a doctor immediately in case of an accident. If you spill the acid on your clothes quickly put them into water – if you re fast enough they will stay OK. You have to return your dead battery to the dealer or service station. Keep in mind that it contains a pound of poisonous lead and half a lit re of acid – that’s definitely a case for professional recycling!

Okay now to test your regulator and generator so that your YAMAHA XS5650 can charge and you don’t look like a moron pushing your XS BOBBER home.

2. Find a really thin feeler Gage like 0.010″ or 0.015″ and hold it pointed down about a half inch away from your generator cover on the engine. Now turn the key on. If your regulator and rotor are working the feeler Gage should slap the case when the magnetic field is created in the rotor. If nothing happens or the magnetic effect seems really weak then go on to the next test because you’re not generating any electricity in your generator on and the XS650 Chopper will need power.

3. On the YAMAHA XS5650 the solid state regulator models all you need to do is locate the green wire at the regulator plug and make a jump from it to ground. The purpose of the voltage regulator is to keep the voltage under 14 Volt on the XS bobber. It controls the electrical current from the battery to the rotor. The rotor builds up an magnetic field and inducts the coils (3 coils) of the stator. If the output of the stator gets to high then the Voltage Regulator interrupts the circuit to the rotor and the magnetic field as well and the output of the stator stops. That bypasses the regulator and allows full battery current to flow through the brushes out of the rotor through the green wire to ground on the YAMAHA XS5650. That causes the rotor to make a stronger magnetic field which in turn causes more current to flow in the stator. If your battery terminal charge voltage jumps up to 14.5VDC when you rev the engine then the regulator or the ground connection for the regulator is your problem.