Exhaust Smoke

Your motorcycle may be smoking for one or both of these reasons.  One, your carburetion is too rich.  Two, your exhaust is fouling with excess unburned oil.  Both can be rectified.  The first by a spark plug check and subsequent changes to pilot jet/air screw adjustment and main jet reduction. If the engine is running fine than the second smokier solution may be appropriate.  It involves a LOT of smoke and an oxy-acetylene torch.

The exhaust is removed and a fire is lit with a flame of oxy-acetylene mix.  Once the fire starts the acetylene gas is turned off and the oil in the pipe becomes the fuel.  The oxygen is still supplied by the torch.  It will burn until the flame consumes the last remnants of oil.  A rosebud tip or a cutting tip, without use of the oxygen lance, can be used.  The only problem with this is the heat might be great enough to burn through the pipe somewhere.  I haven’t found this to be true yet.  It will burn any aluminum that might be in the pipe and it will certainly burn any fiberglass if any is present.

Recommended ratio is 20:1.  That is a quart to 5 gallons.  This is recommended for all Impala’s, Scorpion and King Scorpion, and 247 Cota’s.  If in doubt check the Montesa parts/owner’s manual for its recommendations.  I recommend you follow Montesa’s recommendations.  Golden Spectro can be used at that ratio no matter what the can says or a parts person might say at any motorcycle shop.  These old engines have marginal bearing sizes.  Most of the Montesa engines use the same bearings as the first 175 Impala that produced about 16 Spanish horses.  A third bearing was added to the power takeoff side of the crank and is somewhat isolated from the crankcase premix on any of the 5 speed Cappra’s and Enduro’s.  Bearing sizes did not change until the VA series in 1976.

Other oils I have tried with success are Full Bore 50 wt., Castrol 2 stroke petroleum base, Yamaha R, Schaeffer’s, and Maxima.

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