Firing on one cylinder
- Thread starter MikeM
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- Jul 8, 2011
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Physically confirm you have spark on RH side. Pull plugs, ground them to cylinder head, turn ignition on (important), kick over and observe. Swap or use new plugs for this test in the event of a bad plug.
Is the RH spark plug wet with fuel?
Do you have compression on the RH cylinder. Turn off ignition, pull plugs, carefully place finger over RH spark plug hole and gently kick through the four strokes. Do same on LH side for comparison. You could have a valve hung open (stuck).
As stated above, check other obvious things such as RH slide is moving, RH choke is cleared.
If indicated, turn off fuel taps and drain and measure each float bowl contents; the volume should be near identical.
Is the RH spark plug wet with fuel?
Do you have compression on the RH cylinder. Turn off ignition, pull plugs, carefully place finger over RH spark plug hole and gently kick through the four strokes. Do same on LH side for comparison. You could have a valve hung open (stuck).
As stated above, check other obvious things such as RH slide is moving, RH choke is cleared.
If indicated, turn off fuel taps and drain and measure each float bowl contents; the volume should be near identical.
Actual back-fireing in the muffler is a sign of intermittent contact in the primary circuit. What happens is, carbs are supplying fuel like they are supposed to but one of your plugs is not firing. Raw gas is getting in the muffler and when that plug does light off the cylinder,,,BANG in the muffler too. You need to find out why the plug is not firing all the time. I'd first check to see if the right plug is wet with fuel. If so I'd check all the Black & White and Yellow & White wires of the primary circuit first, including those to the condensers. Tug on them making sure the connections are tight and look for damaged insulation causing a bare wire to ground.
Be patient, keep in mind everyone has good ideas here, but it is hard to diagnose problems without having the bike right in front of you.
Do the easiest checks first and note your results and conclusions.
Be patient, keep in mind everyone has good ideas here, but it is hard to diagnose problems without having the bike right in front of you.
Do the easiest checks first and note your results and conclusions.
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- Jul 25, 2010
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Vith Zee Contact Breakers , firing it up on a dark overcast moonless night , with the points cover removed , can reveal much .
If you dont have a dark overcast moonless night , youll have to turn off the garage lights & shut the door .
One Strand of wire free protuding at the contact breaker connection can see you undone . OBVIOUSLY there should be No Tracking
( current flowing / spark track ) Other than AT the Contact Breaker Contacts .
Dont pull into a gas station and put your ha nd into the distributor leadfs to see if theres ' leaks ' .
Stop somewhere dark and
open the bonnet . Pays to have a flashlight with you so you dont trip over the cat . :wink:
someones probably mentioed a length of 1/8 " neopreene tube in your ear :shock: as a stethoscope ! , wandering the other end about the top end & carb / manifold joint faces you should hear
if theres any errant hissing , which signifies atmospheric interaction . That should only be occuring at the intake . If its elsewhere , its a LEAK .
If you dont have a dark overcast moonless night , youll have to turn off the garage lights & shut the door .
One Strand of wire free protuding at the contact breaker connection can see you undone . OBVIOUSLY there should be No Tracking
( current flowing / spark track ) Other than AT the Contact Breaker Contacts .
Dont pull into a gas station and put your ha nd into the distributor leadfs to see if theres ' leaks ' .
Stop somewhere dark and open the bonnet . Pays to have a flashlight with you so you dont trip over the cat . :wink:
someones probably mentioed a length of 1/8 " neopreene tube in your ear :shock: as a stethoscope ! , wandering the other end about the top end & carb / manifold joint faces you should hear
if theres any errant hissing , which signifies atmospheric interaction . That should only be occuring at the intake . If its elsewhere , its a LEAK .
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- Aug 29, 2010
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- 682
Well ... my guess it is it is an "intermittent" bad coil. Switch coil to other side, see what happens. Next, I would switch condenser to other side. Do one thing at a time, as intermittent problems are THE hardest to troubleshoot, and find. You WILL find problem eventually.
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- Dec 10, 2008
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From idle through 2500 rpm the fuel is almost entirely supplied by the idle circuit [when under no load].
If you ride it and twist the throttle beyond 1/2 throttle and the bike suddenly starts running on both cylinders, then you can be assured the problem is a carburetor idle circuit blockage. It can be difficult to clean out. This would be common after setting over the winter, if the carbs were not drained and preferably blown out with air.
If twisting the throttle does not make the engine run on both cylinders then you likely have an ignition problem. Rust or dirt on a contact would be common or I have also seen where the grease on the points pivot got so hard the points would not close.
Corrosion in the wiring to the coils or points would also be a possibility. Jim
If you ride it and twist the throttle beyond 1/2 throttle and the bike suddenly starts running on both cylinders, then you can be assured the problem is a carburetor idle circuit blockage. It can be difficult to clean out. This would be common after setting over the winter, if the carbs were not drained and preferably blown out with air.
If twisting the throttle does not make the engine run on both cylinders then you likely have an ignition problem. Rust or dirt on a contact would be common or I have also seen where the grease on the points pivot got so hard the points would not close.
Corrosion in the wiring to the coils or points would also be a possibility. Jim
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