Dropped Cylinder

[godsend1]

I'll throw this in here for now,

I lost my right rear cylinder last week, I was riding 2 up and noticed it toward the end of the ride, it would fire at high RPM but not at idle-to 6-7k. It is getting spark looks good and shocked me good to, I threw an old known good plug and still no love. Strong smell of fuel, cyclinder remains cold.

I guess I need to check the coil, any other ideas based on the symptoms?

A little more info, it rode fine for 20 miles or so, then about a mile from home, it just started missing, then the fuel smell and like above would fire at higher rpms but not at idle etc.

 

[one2dmax]

Could be bad TCI or even pickup coil letting it only get random spark.

Sean

 

[maleko89]

What's the Ohm reading from boot to ground? Does it change if you wiggle the wire? Could be bad boot and/or plug wire.

 

[Thevmaxrider]

What's the Ohm reading from boot to ground? Does it change if you wiggle the wire? Could be bad boot and/or plug wire.

+1 to this advice and I would like to add a couple of other things to try. Disconnect the plug wire from the coil, trim 1/8" off of the wire (or better yet replace the wires entirely), put dielectric grease in the hole (not too much or it will come out of the hole and make a mess) in the coil, pull the rubber grommet back from the coil, stab the wire into the coil until it bottoms out, and then move the grommet back into place and screw on cap. Repeat this procedure for the boot end of the plug wire as well. I found that before going to COPs the wires tend to corrode and break off inside the coil and boot which can and will cause an intermittent firing issue that gets worse at low RPM's.

 

[naughtyG]

It sounds EXACTLY like the problems I was having a few weeks ago.

They were due to a rusty tank and a crapped out old fuel filter, sending dirt into the carbs, stopping the needle valves from sealing, dumping tons of fuel into the cylinder and flooding it. I was losing mostly #1, ran like shit from 0-5000rpm then picked up ok. I was getting about 50-75miles to a tank, and could smell gas as soon as I stopped too..

The Fix:
- first check your fuel filter. It may look ok from outside, but be decomposing inside (mine did). You can't tell until you cut it open (destroying it) so just replace it.
- drain your fuel bowls and look at the gas - has it got dirt in it?
- then check your tank. Empty it (there's a drain plug at the bottom) and inspect with flash light. If it's rusty you will need to treat it or replace.

If you find dirt, it's most likely that after fixing the tank/filter problems, you'll also need to take your carbs out and thoroughly clean them. That's what I did - replaced tank with treated one, renewed fuel filter, cleaned carbs, and now it runs like a champ again.

Hope this helps..

 

[godsend1]

Thanks guys, I'll have some time tomorrow night and I'll give these things a shot.

 

[godsend1]

What's the Ohm reading from boot to ground? Does it change if you wiggle the wire? Could be bad boot and/or plug wire.

LF:16.9
LR:17.4
RF:17.2
RR:16.6 problem cylinder

No variations when wiggling. I'll look at the carbs next.

 

[godsend1]

Could be bad TCI or even pickup coil letting it only get random spark.

Sean

I ran it with a plug in the boot , and another in the cylinder, it was sparking pretty good against my hand and the cylinder wall.

 

[godsend1]

Idle circuit clogged, shotgunned the carb and cleared the problem.

NaughtyG,

Ya, the fuel tank has some rust in the bottom, when I drained the carb there was some rust present. I put in a new glass fuel filter last year. I guess I get to coat the tank. Blargh!

 

[naughtyG]

Idle circuit clogged, shotgunned the carb and cleared the problem.

NaughtyG,

Ya, the fuel tank has some rust in the bottom, when I drained the carb there was some rust present. I put in a new glass fuel filter last year. I guess I get to coat the tank. Blargh!

Ya - I had the exact same problem. Trust me, it only gets worse.. And no fuel filter will stop that fine rust dust from getting into the carbs.

If it helps at all, I still have my rusty tank. It also needs coating, but at least it's out and dry already, so you could just do it while still riding, and do a straight swap when ready. I'll let it go cheap as I haven't had time to coat it yet.

 

[godsend1]

Ya - I had the exact same problem. Trust me, it only gets worse.. And no fuel filter will stop that fine rust dust from getting into the carbs.

If it helps at all, I still have my rusty tank. It also needs coating, but at least it's out and dry already, so you could just do it while still riding, and do a straight swap when ready. I'll let it go cheap as I haven't had time to coat it yet.

Thanks for the offer, I'm cash strapped at the moment , so I'll have to pass.