Misfires while raining

[Me_Rock]

Howdy all,

The temperature in eastern Washington has been creeping above forty degrees recently, and that inevitably leads to riding the ol' Steamer in the rain. My lovely English lady has been a little bit grumpy when it's wet out. She will misfire under acceleration and idles roughly. Even after being fully warmed up, she'll expel some white exhaust.

That said, she behaves beautifully when the weather is dry. No scary smoke or misfiring drama. My current hypothesis is the infiltration of water in to the questionably airtight air box assembly. Air boxes are expensive, however, and it would be great to get an outside opinion before purchasing a new one.

Any ideas?

Thanks!
Me_Rock

[windscreenman1]

 :thumbsupMine used to do that I would check the tank breather pipe it will probably be blocked and allow water to track back to your filler cap and infiltrate your tank if this is correct you will nedd to drain your tank and douse it with a water reppelent and let it dry out then drain your float bowls refil you tank and drop anadditive in for good measurethen giveher a run also check the rubber seal under the filler cap these have been known to perish too mine was crackedand they are not expensive to replace
Hope this helps your cause
Cheers

[Bixxer Bob]

Good reply WSM1 

Being from the NE myself, I am not at all surprised that you had the answer; God knows, it rains enough!

My Girly was lucky in that the first time I had rough running in the rain, I actually saw the problem develop.  It was at Shildon Jet station and pissing down.  When I opened the filler cap I saw about an egg-cup-full of water run into the tank.  I had about 200 miles to go and she ran rough for about 25miles then settled down.  When I got home I drained the tank and found out of the 3 litres that was left, about half a litre was water.  My guess is that over time the water level had risen to just below the fuel pickup  and the-egg-cup full  was the limit and so she was picking up water and fuel till the water level dropped again

[windscreenman1]

Cheers bob
I know that garage well
Its good to share knowledge
Thats why we are all here isnt it ?

[Mustang]

over the years I've seen several things cause that scenario ............
1. is certainly the possibility of water in the fuel tank
2. seen it when coils start to go bad
3. have seen those same symptoms when the valve clearances are going to zero on one or more cylinders .
4. and the NUMBER 1 problem is dirty carbs after sitting for the winter

#1 and #4 is where I'd start
#1 is easy pull the hose off the petcock put it reserve and drain some fuel into a bottle .see what comes out
water will be obvious .
# 4 is next CLEAN THOSE CARBS
if you haven't solved it by now CHECK your valve clearances (especially if they haven't been done in a while)

[Me_Rock]

Thanks for the responses!

I will investigate the water content of my gasoline. I didn't think about that.

I'm guessing the coils on the bike are original, and this bike hasn't had a good life. What do failing coils on a Steamer act like? I once had an '83 Honda Ascot that had really bad coils, and it would refuse to start up when it was already warm. The Steamer starts reliably.

To my knowledge, the valves were last checked on this beast about 12,000 miles ago. They didn't need any adjustment. The shop manual says it's time to check them again. Will I need special tools to check clearances? I've only experienced misfires twice, and both times it was raining. If the problem is indeed the valves, wouldn't it be acting up all the time, and not just when it's raining?

I've been riding the bike (and getting her up to temperature) at least a few times a week. The carbs shouldn't have any cobwebs left from winter. Especially after the half can of sea foam they've gone though. That said, I haven't had the carbs open since last Spring.

Thanks!
Me_Rock

[sweller]

I live in the UK where it's fairly damp.  Hence our green and pleasant land.

My Tiger's misfire in wet weather was down to one of the coils getting wet.  I sprayed them with "Waxoyl" (a waxy rust preventative and moisture repellent).  Now no problem in the heaviest downpours; even without a front fairing or lowers.

On the whole we don't have too much of a problem with contaminated fuel here - I only had one bike that had issues with water in the fuel (an MZ) and that was more likely to be down to internal condensation.

A friend of mine was always concerned about the problems he thought he was having with water ingress around the filler cap on a Triumph Sprint.

[Mustang]

Thanks for the responses!

I will investigate the water content of my gasoline. I didn't think about that.

I'm guessing the coils on the bike are original, and this bike hasn't had a good life. What do failing coils on a Steamer act like? I once had an '83 Honda Ascot that had really bad coils, and it would refuse to start up when it was already warm. The Steamer starts reliably.

it's usually the Gill coils that go tits up , and the usual failure is a misfire or complete missing cylinder up to around 3500 - 4000 rpm , and then once past that rpm range it comes back alive nice and strong . the cause is an internal break on the wiring in the windings of the coil and the lame OEM spark has a hard time bridging the gap until the rpms come up . If your bike has the PVL coils you are probably fine , if it's a 98 model you got Gill coils .

To my knowledge, the valves were last checked on this beast about 12,000 miles ago. They didn't need any adjustment. The shop manual says it's time to check them again. Will I need special tools to check clearances? I've only experienced misfires twice, and both times it was raining. If the problem is indeed the valves, wouldn't it be acting up all the time, and not just when it's raining?

no tool reqd to check them and you can always pull the cams to replace the shims , the tool just eliminates having to pull the cams .