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Bogging down in the rain

6K views 22 replies 9 participants last post by  punxsybob 
#1 ·
So I rode my 95 Shadow 1100 about 90 miles in hard pouring rain with no issues a few months ago. Then around Dec it rained lightly again and my bike bogged down as I was heading home from work and I wasn't able to figure out why- Today I rode it to work in light rain and it started doing this bogging down again. When I got to work, I tried pulling the drain plug under the airbox and nothing came out, so I don't think I have water building up in my air filter.
Any other ideas that I can check? I have my tools in saddles so I can open stuff up later in the day if work gets slow, before I go home...
 
#4 ·
HAHA definitely likes the girl better lol

I would be looking at your sparkplug wires.
hmmmmm I'll have to look into that. What am I looking for? They visually look okay. Spark plugs themselves are probably less than 3 months old (iridium)
 
#6 ·
Depends if you mean bogging by a roughness and misfire, or a slowing down loss of power like a fuel starvation. One cylinder miss? Or complete engine loss of power?
 
#7 ·
Slowing down loss of power .

Also - It stopped raining so I was able to get home okay - except it did lose power and shut off.... but that was because I forgot to turn the petcock into reserve LOL .Scared me for a second then I looked at my miles haha....

I'll try the sprinkle water on wires trick per suggestion.

thanks guys
 
#9 ·
Big mouthful of beer and spray it! No just kidding.


If you can duplicate the symptom, stop and drain the fuel bowls to see how much fuel is inside each carb.
I don't know why that would be the case unless the fuel pump connector is corroded and when rains and gets wet it open circuits ???
Since the whole engine is involved not just one cylinder I am thinking a fuel starvation.
 
#11 ·
In both cases I'd wonder if the air filter is getting wet enough to clog? I don't know the bikes in question so don't know how exposed the filters are, but that's one place I would look. Even if the box isn't getting wet, the filters may be drawing in and trapping enough moisture for it to be an issue.
 
#15 ·
Eh, I was never able to figure it out lol. I hosed the hell out of the bike and could never get it to replicate the issue at home. I think I needed to dip it in a swimming pool to get it more wet. Only happened when it was raining and I was riding. Weird. I changed spark plug wires just to be safe and didn't fix it either. Air filter cabin stayed dry (it's the one that sits below/inside the seat). I'm guessing maybe a vacuum hose had a leak and was sucking in the water from the air when moving? Dunno. Doesn't rain in LA often enough to concern me and I have another bike now that doesn't mind the rain lol :) (my 99 Aero)

Cellulose filters don't like to get wet, plus when's the last time you changed the air filter.
I had changed it right around then. I experimented with taking it off and it ran the same. But yes it had a clean filter.
 
#13 ·
@punxsybob, that is weird about one plug on each cylinder being a different color. Mine do that too and I though it was because mine uses some oil. But the spark system is a circuit that power goes into one plug and through the head as ground and out the other plug in reverse. So strange things can happen with a dirty plug or rich mixtures, wire resistances, etc.

Almost like the waste spark systems but with both plugs in one cylinder.
 

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#14 ·
The air filter is pretty well protected but I will remove and see if it clears up the rough running next time this happens. Never heard of the waste spark system but , OK. Could the 2 dark plugs mean that I am running too rich? The PO had installed dial a jet - maybe I need to dial back 1 notch...
 
#17 ·
Also see my the post I just made - routing of wires and perhaps a coil arcing across with humidity.


"Wasted Spark" is common in 4cyl bikes and some cars as well. My CBX is a 4cyl bike but has 2 coils (the same as the Shadows). When Cyl 1 is due to fire, Cyl 3 also fires as the power goes from the coil so plug 1, through the gap and into the head, across the head to P3, across the gap, then back through the plug to the coil to complete the circuit. So the spark on P3 is 'wasted'.

On the Shadow's it's not 'wasted' but they use the same style of system. In fact, it's probably a benefit on the Shadows as you get the fuel ignition from both sides of the cylinder, allowing a faster and more even burn.

I'm not sure on the plugs. If Swifty hadn't confirmed it I'd wonder if you'd pulled all 4 and were mistaken as to which was which (ie 2 dark ones from one cylinder :) ) - and yes, something I have done!.

Have you re-checked this after a few days or weeks of riding? It should be that the two are the same from each cylinder but if there's an oil leak letting oil in at some stage (eg around the cap on the side the timing chain is on - a leak in the seal on that cap could maybe let some oil be drawn in while the bike is cooling and there's a small vacuum in the cylinder). If it was a once-off I'd suspect something was left on 2 of the plugs from manufacture or handling, and it's just a fluke it happened to be those two. But I am kinda grasping at straws here :)
 
#18 ·
It almost sounds like you may have weak coils. Have you checked your battery to make sure it is giving full power to the coils? You may need to ohm out those coils to see if they are within specs. Another cheap trick is to use an infrared thermometer and see what your exhaust temps are. This will let you know if they are burning both cylinders around the same temp. If there is a big difference you may have a fuel delivery difference, leaking spark or maybe a bad plug. You're not getting water in the tank from the rain are you?
 
#19 ·
Hmmm...Spark unit. Maybe on to something there. This bike has been "bobbed" and the spark unit that sits on top of the battery is open to elements (not fully enclosed like a stock bike) Maybe if I add dielectric grease to the connections on this unit, it would help during the rain?
 
#21 ·
Wrap a plastic bag around it also if it is hidden under a seat or something.
 
#23 ·
Well....we bagged the controller and added another shield where rain may have been getting in. Got caught in rain riding home and it seems to be doing just fine for now. Will be adding more here if it acts up again. Thanks for all of the advice. Saw a sign at "BILLET PROOF" on my way home. Said "To ride or not to ride....now that's a stupid question! This fix will help keep me riding all year long!
 
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