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Twirl Method of Adjusting Valves

Helpful notes:

Remove the spark plugs, it's much easier to turn the engine over without them.

Take some white or silver paint and paint the timing marks on the flywheel so they will be easier to see. It helps too if you put a few dots of paint before the marks. You can do this after painting the 2 marks by putting the bike in gear and gently pushing it backwards. Put a few drops of paint on the flywheel to warn you before the real marks come up, this makes it far easier to stop the engine on the marks.

Procedure:

Spark plugs are removed. Bike is in neutral, engine cold. Valve covers removed, plug on inspection hole removed.

Many feel that this is a good time to check the head torque. If you do this, use some caution as the 650 bolts are very easy to strip. They are to be torqued to 20-22 ft. lbs. The 750s are 40-42 ft. lbs. Make sure you loosen the nut some before torquing, as the nut will tend to 'freeze' in place and this gives a false high reading.

Rotate the engine slowly with the kickstarter until the 2nd timing mark is in the center of the window. This is Top Dead Center.

At TDC, one side is ready to adjust, the other side is between Exhaust and Intake stroke. If the valves have been well maintained in the past, you can tell which is ready by twirling the pushrods between thumb and forefinger. The side that's ready for adjustment will have both pushrods so they can be easily spun, the other side will have one or both that are tight.

If the pushrods are all too tight, you'll have to watch the valves move on one cylinder as you rotate the engine. As the exhaust valve slowly closes on one cylinder, start watching for the timing mark. When it's centered adjust the OTHER cylinder.

To Adjust: Grasp the pushrod between thumb and forefinger and try to spin it. It should rotate freely and even keep spinning a bit. Wiggle it from side to side - if it moves around much it's too loose. Loosen the 13 or 14 mm nut (varies by bike) that locks down the valve adjustment screw. Make sure you turn it a couple of times so the adjustment screw has plenty of free movement, or else when you start to tighten the adjustment screw the locking nut will bump and you'll think it's tight. Using a 10 mm wrench, tighten the adjustment screw until you start to feel a little resistance - this means it's tightening against the pushrod (unless the nut is bumping, see above). Try twirling the pushrod, it will probably be a little tight. While twirling, back off the 10 mm adjusting screw until the pushrod twirls easily but doesn't move a lot from side to side. Hold the 10 mm wrench in place so the adjustment doesn't change, and tighten the locking nut down. Before tightening the locknut the final bit, I slightly loosen the 10 mm adjustment a hair just to make sure the valve isn't too tight. Lock it down and re-check your work.

Do the other valve on this cylinder the same way.

Now rotate the engine one turn until the timing mark is back in the center of the hole. Adjust the valves on the OTHER cylinder using the same procedure as the first one.

When finished, rotate the engine one turn again and re-check your 1st cylinder, then rotate again and re-check the 2nd one.

Replace the valve covers, spark plugs, and inspection hole cover and fire it up!

Vance Blosser

 

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