QuestionMy bike (97 Honda Shadow VLX vt600CD) decided 2 run on 1 cyl. Makes spark (@ all 4 plugs) has
compression. Norm plug color. Got over 100k miles on it(i got it 4 years ago w/ 10k on it) I NEVER adjusted the valves or changed plug wires.
Recently cracked rear mounting tab on tank & Its leakin a bit of fuel, Ill weld it today! 1 day it was fine & the next it wasent. Rdin it I could feel it tryin 2 kick in but it dosent. Tried pullin the choke out a bit while ridin it & it didnt get no better. I thought if 1 wasent firing the fuel would B getting pumped out the exhaust but I didnt see or smell it.
I was guessin mabey somthin like the rectifier bridge or the fuel pump on Is way out , mabey even a weak coil. BTW I modified the stock air intake & am using a UNI filter also aftermarket pipes w/out baffels & a Factory jet kit usin whatever the biggest jet in the box was. I still needs a bigger jet but i restricted the air intake untill the plugs were a nice golden color.Could never pass emissions since the pipes were added, old pipes were the same but skinnier & I guess that made the diff. I know its hard 2 answer a ? like this without seein it but i figured it was worth a shot. Thanks
AnswerHi Tm Hyde,
The way I interpret the carb, pipe, and air intake modifications, you've got some tuning issues going on. That may be the source of the problem. Like you said, really have to be present and perform some checks to accurately diagnose the problem.
It should be known that spark plugs may arc when removed form the cylinder head and grounded against the engine, but may not arc under the extreme loads of compression.
The first thing to do is try new plugs. Next, measure cylinder compression and perform a leak-down test if necessary. These tests will determine the condition of the combustion chamber's sealing properties, or the condition of the engine.
If all checks within specs, move on to tuning the carb and checking ignition. If not within specs, repair and then continue on.
The suspected non-firing plug may have a defective cap or secondary or HT lead causing what is known as "flash-over." Electrical current travels over the exterior secondary lead instead of thru it. You can check this by misting water over the wire and cap with engine running. Dosen't take much water and needs to be a mist. If you see the arc and you will if defective, replace bad components. CDI's usually affect all cylinders. I've only seen three defective ignition coils in 25 years. Coils could be bad, but I doubt it. Check wiring and multi-connectors. Use dielectric grease on all connectors. This helps to prevent water shorting and corrosion. After washing, water can last in a connector for days before evaporating, and may cause problems such as you've described.
Try this new information and advise.
Respectfully,
Mark Shively
