Misfire in rain

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nigb
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Misfire in rain

Post by nigb » Sun Jun 11, 2017 7:52 am

Hi I have had my KR over 10 years now & have done numerous long trips on it. However ever since I have had it if it rains it misfires like crazy especially under load & quite often just cutting out all together. Spraying WD40 in abundance helps for a short time & then it starts missing again. I recently replaced the copper HT leads, NGK spark plugs & caps & still have a problem. Anyone else experienced this with their KR?
2008 Ducati 1098
2003 Triumph Sprint
2003 KTM 450EXC
1975 h***a 400-4 (fully restored)
1984 KR 250

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Binetta Steve
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Re: Misfire in rain

Post by Binetta Steve » Sun Jun 11, 2017 8:45 pm

I know this sounds wacky, but have you tried removing the fairing , then in a garage or car port ( so its a bit darker) get a hand bottle sprayer and spray an aerosol of water from the coils down. If anything is arcing to earth you will see the blue flashes.

Given you have a fairing on and the engine is pretty hot then this cold dousing should show up shorting fairly quickly.

If dousing it with WD works then the silicone is finding the break.

Its strange , I would have thought changing the leads and plug caps would have had a positive result. Its not something silly like the kill switch or side switch earthing is it?

nigb
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Re: Misfire in rain

Post by nigb » Mon Jun 12, 2017 12:45 am

Doesnt sound wacky to me Steve sounds like a good idea. I am away from bike for 10 days (its at another house) so I will give that a go then. Yes I thought the plugs, leads & caps would have sorted it. One thing I have noticed is that it starts a lot easier than it used to do. Thanks for the reply I will let you know how I go.
2008 Ducati 1098
2003 Triumph Sprint
2003 KTM 450EXC
1975 h***a 400-4 (fully restored)
1984 KR 250

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StrokerBoy
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Re: Misfire in rain

Post by StrokerBoy » Mon Jun 12, 2017 9:27 am

Never had that problem with mine, but then it hardly ever rains here... :lol:

Plug caps and leads would have been my first attempt at a fix too. Both CDI units are pretty exposed, check the connections. Might be worth making some sort of temporary shield from cardboard next time you ride in the rain, see if you can prevent the water getting to wherever it's causing a short.
Kawasaki KR250 Tandem Twin (x4) & KS-II 80,
Yamaha RD350LC,
Suzuki GSX-R750RK & RB50 Gag.

nigb
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Location: Australia

Re: Misfire in rain

Post by nigb » Mon Jun 12, 2017 1:24 pm

LOL Tim its because it hardly rains here it hasn't been much of an issue but the last few rides have been wet & it has been a nightmare trying to get the bike home. Yes the cdi boxes are exposed but the fairings do prevent them them getting wet for a while. If I am driving down a dry road & it starts raining the misfiring happens very quickly & also continues whilst the road is wet after the rain (roads dry out very quick in Oz). I have tried putting duct tape between the bottom of the radiator & the belly fairing thinking the water was spraying through there to no avail.
Curiously my h***a 400-4 does it also but they were renowned for it. WD40 normally clears that for a while.
2008 Ducati 1098
2003 Triumph Sprint
2003 KTM 450EXC
1975 h***a 400-4 (fully restored)
1984 KR 250

nigb
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Location: Australia

Re: Misfire in rain

Post by nigb » Mon Feb 26, 2018 10:53 am

With the VJMC Rally down under looming next week I have endeavoured to rectify/improve this misfiring problem.
I have:
Replaced earth chassis to battery lead that looked a bit suspect.
Detected a hot spot visible thru the 6 pin connector going to ignition switch - Brown wire that gets switched thru to white wire when ignition on. Replaced connector with one from another loom.
Now:
Bike starts 1st kick every time hot or cold
starts on 2 cylinders rather than 1
with bike running sprayed copious amounts of water around anything electrical - no problem engine continues to run.

Been waiting for a rainy day for months (can be a problem in Oz!). Yesterday it poured so left bike out in rain for several hours, then it started 1st kick. Riding down flat road no problem but then when going up hill total lack of power (but no misfiring!). When I got it home I left it running & was inspecting connectors when I got a zap from the right hand cdi unit.

What I am now going to try is putting heatshrink around all off the connectors & try that. Weather forecast for trip to rally is mixed so I will take my chances with that.

Any other suggestions appreciated !
2008 Ducati 1098
2003 Triumph Sprint
2003 KTM 450EXC
1975 h***a 400-4 (fully restored)
1984 KR 250

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StrokerBoy
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Re: Misfire in rain

Post by StrokerBoy » Mon Feb 26, 2018 11:32 am

That zap you got is a big clue ! :lol:

Does it cut out altogether or just run on one when it's misbehaving ?

In the RC car world, a popular mod is to encase vulnerable electrical components in a rubber balloon, and cable-tie the opening to prevent moisture getting in. Pretty sure you'll be able to find lime-green balloons somewhere. :mrgreen:
Kawasaki KR250 Tandem Twin (x4) & KS-II 80,
Yamaha RD350LC,
Suzuki GSX-R750RK & RB50 Gag.

nigb
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Re: Misfire in rain

Post by nigb » Mon Feb 26, 2018 11:53 am

Yes Tim that is why i suggested the heatshrink! Like the cable tie idea too. What I cannot figure out is that no one in the wetter parts of the world hasn't had the same problem. I even read through your original tale of picking up your 1st KR in the pouring rain for clues to no avail!
I will report back on how I go.
2008 Ducati 1098
2003 Triumph Sprint
2003 KTM 450EXC
1975 h***a 400-4 (fully restored)
1984 KR 250

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StrokerBoy
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Re: Misfire in rain

Post by StrokerBoy » Mon Feb 26, 2018 4:54 pm

Yeah, I've not had any wet-weather running problems on my KR at all, lucky I guess. My TDR and 3MA were both prone to it though, as was my DT125R.

Good luck. Looking forward to pics from the rally. 8)
Kawasaki KR250 Tandem Twin (x4) & KS-II 80,
Yamaha RD350LC,
Suzuki GSX-R750RK & RB50 Gag.

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