Givi EA102B tank bag £79.50
Tested by Martin Fitz-Gibbons for six months, 1000 miles
Modest-looking but well-made, smartly designed and highly versatile magnetic tank bag. There’s a resounding sense of considered quality throughout, from the handy plastic loops on the zip tabs, to the neat internal pocket for the rainproof cover, to its four ultra-strong magnets. The main compartment expands up to a huge 25 litres of storage, with a large clear map pocket on the top, and some foldout rucksack straps on the base. Even loaded, this Givi clung to my Triumph Scrambler’s metal tank so tenaciously I braved 10 miles of bumpy off-roading standing up, and it didn’t shift. Massively impressed – and if £79.50 seems a touch steep, then right now Sportsbikeshop are offering it for £65.40. That’s a great price for a quality bit of bike luggage.
Get to know your power valve
The power valve is a cylindrical-shaped form that is located within the cylinder just after the exhaust port on Yamaha’s legendary strokers. It rotates a few degrees backwards and forwards, raising and lowering the height of the exhaust port, which gives the engine improved flexibility for the road. Refurbing the valves should be done with the cylinders removed.
How it’s put together
Yamaha fitted the YPVS system to many different models, and they’re all pretty similar in terms of design and actuation. They’re made in two halves which are bolted together in the middle. The bolt that holds them together usually has a 4mm Allen head. If it needs replacing only use the original Yamaha item otherwise you will risk causing damage to the bike.
Check rings and install
Check the condition of the seals and O-rings which sit on either side of the valve. The original parts are still available from Yamaha so opt to use these as opposed to pattern parts if you need to replace anything. Fit the power valve into the cylinder, then turn it to make sure it moves freely backwards and forwards.
Open the valve
The next step is to turn the power valve to the fully open position and check that it lines up exactly with the top of the exhaust port. You can check this either by looking from the piston side of the port or by the exhaust side. In the open position, the exhaust gases will be completely free to flow – maximising the performance of the engine.
Check the cables
The valves are actuated by a servo motor and cables. The motor rotates the valve backwards and forwards, and the cables take it in turns to pull depending on whether the valve is opening or closing. Look for signs of fraying near the nipple ends and where they mount on to the servo motor.
Don’t forget the joint
On twin-cylinder bikes each cylinder has its own power valve but only one side is moved by the cables and pulley. The other valve is actuated via a linkage to the driven one. Quite often this linkage can become worn or loose, so give it a check and tighten up/replace if necessary.
On your marks…
The power valve is set by lining up a hole in the pulley with a hole on the cylinder. With the cables fitted and the pulley bolted on, you can then start to check the position. If you turn the ignition on, the servo motor cycles the power valve to closed and then rests in the open position. It’s at this point that the hole in the pulley should line up with the hole on the cylinder.
Get the right slack
Adjust the cable so that the hole lines up precisely, the cables should not be too tight. You will need to turn the ignition off and on several times to make the perfect adjustment. Using an 8mm spanner, adjust the freeplay in the cable by turning back the adjuster one quarter of a turn from tight. Tighten the locknut using a 10mm spanner.
It’s all about the timing
Check the timing and position of the valves by removing the exhaust and getting under the bike and shining a torch into the exposed exhaust port. Get someone to turn the ignition on to trigger the power valve initiation cycle. As it moves and then comes to rest, make sure the valve is perfectly flush with the top of the exhaust port. Do this for both cylinders.
Refit the cover and ride
Refit the power valve pulley cover. Check that the cable locknuts are tight. Be sure to refit the rubber surround that covers the threaded section and apply a little grease to make them slide over smoothly. Finally, take the bike for a road test and make sure the engine revs correctly throughout its rpm range, and delivers a wide spread of power with no steps or flat spots.