Bogging down/stuttering after it rained

[beardedmonkey]

Left my bike at my gf's and it rained overnight. Rode it home in a downpour but it was fine. Covered it up, took my car to work. Got on a day or two later and it was stuttering like crazy. Gunned it and it hesitated, hesitated... then died. Started it, it hesitated, then I revved it and it did the same thing, then started popping (backfiring) like crazy and then cleared -- I thought whatever was in there had burned off. Then a little while later it started doing it -- rides fine but when I open it up it seems to be lagging, and occasionally it will hesitate/stutter. Been doing that since it rained (four days ago), and it hasn't rained since.

I'm also the guy who had all sorts of problems with the shop rebuilding my carbs, but I finally got it back about 1.5 weeks ago and it was fine... until I rode it in the rain.

Thoughts?

[7981GS]

What model bike and year?

Eric

[MisterCinders]

Any mods to the bike, especially pod filters? Those can react badly to rain, particularly the cheap paper filter versions.

[beardedmonkey]

It's a '78 GS 750, and nope, no mods. But, I finally burned off that last tank (careful not to run it through the reserve though -- they cleaned it, but still, who knows what lurks at the bottom of that tank!), refilled it, and voila: runnin' like a top. Phew!

[beardedmonkey]

BTW: Mistercinders, that is a SWEET bike!

[7981GS]

Throw an entire can of Berryman's B-12 carb/injector cleaner in the tank and forget about it.
Use a half of a can in each of the following two fill-ups.

Eric

[beardedmonkey]

Throw an entire can of Berryman's B-12 carb/injector cleaner in the tank and forget about it.
Use a half of a can in each of the following two fill-ups.

Eric

Is that to clean out the tank so I can rest assured I'm not allowing 34 years of gunk into the engine when I let it run into the reserve, or is that to deal with rain-fouled gas?

Also, it rained *again* and for some dumb*** reason I was caught without my cover. I managed to make due with garbage bags and a roll of tape, and later I rode it home without any problem -- which is good because I just filled up. Had I not gotten so lucky, I guess I'd just siphon out the gas... but what exactly does one do with 4.5 gallons of bad gas? How would I dispose of that? Giant bonfires are out of the question since I live in the city

[mrbill5491]

Think I would pull the tank and thoroughly clean it out. Check the seal around your tank cap, sounds like water could be leaking in that way.

[Dave8338]

Is the little metal flipper tab for the gas cap lock cylinder, working correctly?

[beardedmonkey]

Is the little metal flipper tab for the gas cap lock cylinder, working correctly?

Could you post a pic of what you mean?

Think I would pull the tank and thoroughly clean it out. Check the seal around your tank cap, sounds like water could be leaking in that way.

What would you clean it with? How would I know if the seal is leaking? Would I need a new cap or would something need to be replaced?

I'm assuming it's gotta be the tank and not water through the intake, since that would have cleared up/burned off after everything dried out, right?

[Gonzo]

Could you post a pic of what you mean?



What would you clean it with? How would I know if the seal is leaking? Would I need a new cap or would something need to be replaced?

I'm assuming it's gotta be the tank and not water through the intake, since that would have cleared up/burned off after everything dried out, right?

The flap he is taking about is the locking fuel door that covers the gas cap.

Unless there is somewhere for water to get into your airbox or something, it sounds like you have a bad seal on your gas cap. I have ridden my bike through some hella heavy downpours, and left it out all night in thunderstorms and never had a issue with it running right. It seems odd to me though that water would get in at all. Gravity alone should be enough to keep water from getting in there. It would have to run up the neck of the cap opening, get in between the cap and tank, and then down inside. I can't think of any place that would allow water to pool deep enough to run over that lip.

There are multiple ways to clean your tank too. Assuming we are talking about derusting it of course. A search will turn up a plethora of methods ranging from pea gravel and a dryer, molasses and water, all the way to fancy chemicals and electrolysis. Choose one and have at it!

[sk843143]

Sounds like you gas cap is leaking......when it rains its letting water in through the the tank vent

[reliant_turbo]

i wonder if its more water messing with electronics/ignition than water in the tank.....

[robertbarr]

i wonder if its more water messing with electronics/ignition than water in the tank.....

Yeah, me too. Do we have any evidence of water in the fuel?

Water in the fuel will settle to the bottom, so if you let the bike sit for long enough, it should be fairly straightforward to siphon off good fuel from the top, down to perhaps 1/8 tank. This fuel should be OK. From there, you might start picking up water, so you can keep a closer eye on what's being drawn out (or simply drained via the petcock).

I'm not 100% sure that draining from the petcock using Prime will pull fuel from the very bottom of the tank, but if you siphon off most of the good fuel first, whatever is left can be agitated and then drained and examined in whatever container you used; in no time, the water (if any) will settle out to the bottom.

That way, you don't have the problem you mentioned, of discarding gallons of possibly bad fuel.

Not an easy process, but it will provide an answer rather than a guess.

[Gonzo]

i wonder if its more water messing with electronics/ignition than water in the tank.....

Good call! My reaction was to say it wasn't water in the gas, but other possiblilties eluded me at the time.