So Fix it

A clogged air filter causes dark smoke to come out of the exhaust pipes. If this is the cause of the smoke, then the bikes spark plugs will also not work. Change the motorcycles filter to remedy the situation.

An open starter plunger can also result in grey smoke from motorcycle exhaust pipes. The starter plunger is a small component of the starter. Repair this problem by removing the bolts from the starters cover to reveal the component. Push the plunger closed and replace the starter cover.

Grey smoke can result from improper fuel levels in the float bowl of the carburetor. Remove the float bowl from the carburetor by taking out the screws. Check the markings on the float bowl to ensure the fuel levels are correct.

Converters contain a honeycomb-like ceramic matrix with thousands of tiny passages. Exhaust flows through these passages, combining with the platinum, rhodium, palladium and cesium on the passage walls to add or subtract nitrogen or oxygen atoms. This gain or loss converts the toxic molecules in the exhaust into more benign forms.

Different countries and unions have different emissions requirements and require different catalytic converters. The European Union disallows the use of nickel in converters but permits copper (which the United States does not). Most large car manufacturers offer several variations on the same chassis to market all over the world. Using more than one converter allows the manufacturer to meet local emissions standards while using the same basic chassis worldwide.

Not all car manufacturers produce their own catalytic converters; many converters are outsourced from specialty catalytic converter manufacturers. Because most cars come with a number of different engine options, manufacturers may need to mix and match different converters to meet emissions requirements for a particular engine-chassis combination.

Typically, milling engine cylinder heads is part of a larger repair called an engine rebuild. The lower portion of the engine block is detached, inspected and cleaned. The cylinder heads are then resurfaced to properly seat the pistons and rings within the cylinders body.

Cars Direct estimates that a common four-cylinder engine rebuild can cost from $400 to $500, and as the amount of cylinders increases, so does the pricing. A six-cylinder vehicle costs about $500 to $600, and an eight-cylinder increases to between $600 and $700. Estimates are as of early 2011.

The extent of damage to the cylinder heads can increase the cost of rebuilding. The more resurfacing that is needed requires extra labor hours to create the correct effect for a properly functioning vehicle.

An unbalanced driveshaft will wobble while spinning. This wobble may create a vibration felt in the steering wheel while driving or may shake the entire vehicle. The driveshaft may wobble only at certain speeds and not be felt otherwise. An unbalanced driveshaft will also cause increased wear to related components that may require frequent replacement.

Driveshafts can become unbalanced for a variety of reasons. A vehicle wreck may bend the driveshaft. The driveshaft may also become unbalanced due to loss of balance weights, corrosion or other damage. Bent or significantly damaged driveshafts may be incapable of being balanced and will require replacement.

Balancing driveshafts requires specialized equipment. A large device similar to a lathe spins the driveshaft and measures balance. Technicians weld small weights onto the driveshaft where needed to properly balance the driveshaft. Car owners should use only an experienced repair technician to tune driveshafts, as the process is complicated.