running bad in bad weather

xjwmx

XS650 Guru
Top Contributor
Messages
8,055
Reaction score
4,888
Points
313
Location
U.S.A.
One time in an extended misty rain I found I had to hold the throttle completely open to maintain any speed, and the bike sounded like it was missing real bad. After 20 mi of this I took an exit and as soon as I had gotten off I ran out of gas and coasted into a school parking lot. I ran out of gas a lot sooner than I expected, because of running like that. I saw businesses about a mile away, so poured gas out of a Peak stove into my take and made it up there and filled the tank.

Few days later somebody was talking to me about bikes and I mentioned that experience and that I suspected something water+electrical and he said no, it's the effect of drawing water into the intake. I thought maybe the air filters (stock '81) had been saturated with water. He said it like it was a common thing. Any ideas and fixes? Just happened that once so far. Maybe it was a perfect storm...
 
^Stock '81 carbs w/stock jetting and adjustment. Stock air boxes, filters, and side covers for '81. Stock ignition too. All in good shape.
 
Well old plug wires and or coils can have problems in any kind of damp weather. My old rat bike I rode to work for 20+ years only ever had a problem starting or running on rainy days. More than once I just gave the plugs and wires a soaking with WD-40 or similar and it would start and run just fine.
 
+1 on your experience. '79 stock running in the rain it would bog badly. It only happened on 2 occasions. Like you I came to the conclusion it was water and the perfect storm.
 
A simple test if it happens again.

Find a place out of the weather, shut it off, wait a several minutes.
Carb ice will thaw and melt much faster than electronics and filters dry out.
Fire it up.
If it runs better, it's likely carb ice...
 
^I hadn't considered that possibility. Also been wondering what would happen if you took a spray bottle of water and started shooting a mist into the carb.
 
Plus one on icing it's way more common than folks realize. A wet misty day on a motorcycle is kind of a perfect storm, high humidity Road's wet, so you run slower, carb is barely open. Carbs can ice even in 80F temps. A big part of why older cars have the vacuum operated heat riser on the air cleaner snorkel. Flivver fliers have a carb heat knob in the cabin. A fair number of newer bikes have electric carb heaters at the venturi for the same reason.
 
Curious..............would the crank case venting hose connected to the air-box help to alleviate this issue ???
 
^Interesting. The hose was there (everything stock). Anybody ever noticed how much air comes out of it?
 
Several guys running aftermarket filters with no side covers have gone very rich in rainstorms as the filters get saturated.
 
Go start up Period's Piece and tell us what comes out of the hose... I'm sure it's indoors with lights.
 
It is but the hose is hooked to the stock air boxes just like yours. I think the short answer is not enough to deice the carbs,
 
Start up Period's piece and tell us what comes out of the hose... lol
 
Ps airplanes are especially susceptable to icing at low throttle ie coming in to land. Easy to not know you have it till something goes wrong and you need to "go around" and find there's no power!
 
I never go on board a plane like that without a parachute.

You know, after I put the stove gas in it, it ran fine, best as I can remember. That five min before the light bulb went on might have been time to unfreeze. Certainly not time for anything to dry much. I bet it was icing. Now where was the cake?
 
Last edited:
Back
Top