#1 Cylinder misses at highway speed

[Bizcocho]

My GS550E has been losing power. Today while climbing a long freeway hill, I pulled the #1 sparkplug wire off. No change! That's why I think it must be missing. At idle if I pull off the same wire it almost dies. Any ideas?

Oh: The other three spark plugs look alike. They are almost new and the ceramic is still white. #1 has brownish stain on the ceramic.

Thanks,
~Rich

[Bizcocho]

I hope someone has an idea; I'm not getting anywhere troubleshooting this.

[Guest]

Screw the spark plug cap off the wire and snip a bit off and reinstall.
Hope this helps

[Bizcocho]

Thanks! I think you're onto something. I had already snipped the wire, but I think the cap may be bad. I couldn't get a replacement today, but I have high hopes.

~Rich

[Bizcocho]

I'm soooo disappointed! Number one wasn't firing at speed and the spark plug cap measured open, so I was sure replacing it would fix thiings. You guessed it - no luck. The engine ran a little better in lower gears and lower RPMs, but still topped out at 55 going up a moderate freeway hill. Then I changed the rest of the caps (why not) and it ran even better, but of course number one still didn't contribute on the same hill.

I haven't been able to figure out how to pull the #3 & 4 wires under load, but Ive assumed that only #1 was missing. The other plugs all look the same. Do you think I could be running on only two cylinders at speed? I could swap the coils and see if the problem moved away from #1. Does this seem like the next step?

Thanks,

~Rich

[Guest]

It might be a coil or a dirty carburetor.

[Steve]

It might be a coil or a dirty carburetor.

I would lean toward the carb, myself. Main jet could be partially plugged, allowing enough fuel through for low-speed operation, but not enough for high-speed.

.

[p_s]

This happened on my GS550ES--and only above 8k rpm--and it turned out one of the wires going into the connector on the CDI box ("ignitor") was just loose. So go over all the wiring.

BTW, when this happened I could feel every time it cut in and out, and I could hear a clacking noise. It would randomly happen, but only at higher rpms.

[tkent02]

Switch plugs from another cylinder, does the problem switch too? If so buy new plugs. If not then:

Switch plug wires 1-4. Just takes a few minutes to re route the wires. Does the dead cylinder switch too?
If yes you have ignition problems, plug wire probably as anything upstream would take out two cylinders. look for bad connections...

If not you have carb issue, partially clogged main jet, fuel level low, clogged passage somewhere, could even be the float valve not allowing fuel in fast enough?
Inline filter not flowing enough?
Is this a later CV equiped 550 or an earlier VM one?
Has this problem just started or did you inherit it?
Is the bike stock, or modded incorrectly, i.e. pipes or pods but not rejetted, etc??

[andrewclaycomb]

I know it seems like an obvious thing but make sure the fuel line isn't kinked. I learned this the hard way.

[Guest]

Switch plugs from another cylinder, does the problem switch too? If so buy new plugs. If not then:

Switch plug wires 1-4. Just takes a few minutes to re route the wires. Does the dead cylinder switch too?
If yes you have ignition problems, plug wire probably as anything upstream would take out two cylinders. look for bad connections...

If not you have carb issue, partially clogged main jet, fuel level low, clogged passage somewhere, could even be the float valve not allowing fuel in fast enough?
Inline filter not flowing enough?
Is this a later CV equiped 550 or an earlier VM one?
Has this problem just started or did you inherit it?
Is the bike stock, or modded incorrectly, i.e. pipes or pods but not rejetted, etc??

Good post................

[Bizcocho]

Thanks for the good ideas. Now I have some direction for the weekend. I hope I'll have a better report soon.

~Rich

[Bizcocho]

Thanks!

My baby is back! It turned out that the #1 carb needed cleaning. I used the good advice I got there to eliminate the ignitor, coils, wires, caps, and plugs. I was 'positive' it wasn't the carb because it had been recently cleaned.


Thanks!

~Rich