Intruders-Alert

My son picked up this 93 vs800. It seemed to run ok at first, but after a few rides it developed a misfire that had grown to hardly firing on the rear jug. I thought maybe it needed a coil, so I bought 2 new ones, no change. Checked both the new and old coils, almost the same numbers on the meter (ohms & volts). Thought I would swap plugs, they are different? Both NGK, but different size sockets. one is an 18mm(DPR8EA9), the other is 5/8 (DCPR8E). ok, WHICH ONE IS CORRECT?
Anyway, swap them and still weak spark on the rear and the exhaust is cold. After riding a mile you can't touch the front pipe, but the rear is hot, but you can touch it.

Thoughts? He will be home from the Navy on Tuesday and I was hoping to have it fixed so we can go ride.

Jason

Wow. 1st is Correct. 2nd is NOT.
Get new Correct plugs for both sides.
You have the same issue with the new coils.. So not coil or boot related.
What do the plugs look like? Dark, white, wet?..
Could be weak battery, filthy air filter or fuel delivery issue unless you're sure it's weak spark.. Did you check color/strength of spark?

I bought the correct plugs and now it runs ALOT better. Still has a bit of a stumble, but I'll give it a few rides and see what happens. I suspect it is burning oil in the rear. I had a Yamaha Virago 920 that did the same thing.

Carb synch and AF adjustments required.
http://intruders-alert.com/viewtopic.php?f=32&t=4139

Stick a finger in the exhausts,if the soot is dry. no problems, if it is quite oily, problem. The usual culprit would be a bad valve stem seal, engine out for this job.

[emoji41]

I too have the same issue (weak spark on rear cylinder). However, I did buy new plugs (DPR7EA-9 NGK) Replaced CDI box, checked both coils (Primary and secondary) and both checked good with 2.9 ohms on one and 3.1 on the other. Checked power going to both coils and seemed fine to me at 12.1 volts and battery was at 12.7-12.8. Checked Stator and all three wires checked fine according to my ohm meter and specs in the book. The front cylinder spark is fine. The rear does spark but it's very weak and orange. I have new coils coming just to be sure to eliminate this as an issue. Any thoughts?

Unscrew the plug cap from the plug wire coming from the coil, trim 1/4" or so off the wire and screw the cap back on. Sometimes that cures the problem.

Inside the spark plug cap is a little resistor. I have had these corrode and cause an issue. Turn the cap up and look down inside, there is a brass colored piece that is slotted. use a good fitting screwdriver and pull it out. turn the cap over and catch the resistor and the spring that holds it tight to the cap. Be careful not to lose either it or the spring. The resistor is small. about the size of a large pencil lead and less than half an inch in length. clean the ends of it and check the spring for rust. I have found corrosion on the resistor AND have found rusty springs that prevented good contract.

Thanks! I will give it a try.