The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: chris_blake on September 29, 2007, 03:19:28 AM
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hi guys hope someone can help . riding along motorway when it starts to rain hard 5mins later loud backfire engine cuts out and dies. i check spark at both plugs both fine all the other electrics lights etc fine while iwas waiting for a pickup about 1 hour later bike restarts slowly at first then fine when i got home i sprayed all the electrics with dampstart sealer . 2days later same thing happens again .iwas wondering if anybody else had suffered the same problem or is there any electrical parts prone to water penetration any help most welcome just one thing electrics make my head hurt so please be gentle with me
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A BMW mechanic told me that if you have the metal plug HT caps, they can sometimes short out and lead to problems. Have you got the metal caps or the plastic NGK ones? Maybe check their condition.
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What year bike do you have ? If you have a bike with the single ignition coil ( dual output ) it is a common trait of the coil to develop cracks in the plastic case. Also how old are the ignition leads from the coil to the spark plugs ?
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My first bet is on the coil and/or plug wires...
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Yep, +1 on the above. Classic symptoms.
I'd swap out wires & plugs 1st for new NGKs, and then look at the coil next if the problem persists.
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the bike is a1986 mono i have hosed the bike down earlier to replicate problem now it wont start even after several hours as for it being the plugs leads or coil this was my first guess but the spark is good the only thing i have noticed now trying to restart the bike is the headlight dimming whilst turning over the engine but the battery is good are these 2problems linked
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By "good" spark, do you mean that it is a fairly bright, blue, wide spark ?
If it is dim and yellow it is weak. The headlight dimming indicates that something is
drawing appreciable current from the battery, which is often the case during starting.
But, something may be drawing too much.... Does the starter spin the engine with
some authority, or is it going rrrr...rrrrr...rrrr ?
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It's probably daft to even ask this. But since no ones mentioned it... have you checked the float bowls for water? Because if you've got good spark, and the motors turning over properly then you could just have a bad case of water contamination in your fuel.
Tony
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the spark is anice fat blue one as for water in carbs i dont think so as it would not have restarted the first 2 times it happened but iwill check them.on the coil issue i dont think it is the early problem type as the bike is 1986 also the plug caps are black hard rubber types any way like i say the spark looks good keep thinking guys i am going to try a few things out ok bike has restarted after drying out overnight a couple of things i have noticed the generator light stayed on for acouple of minutes even revving off idle it then went off also a lot of condensation in head light i have a nasty feeling this will turn out to be some sort of electrical gremlin in which case i will have to get help can any one recommend someone in the romford essex area heres hoping.
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This is what caused me to convert to NGK cap in 1997. Stopped in the rain. It doesn't help if your caps and wires are old, either. I change mine every two years just like my fuel line.
It looks like you are in the U.K., but here is my source in the US. He is a Yamaha XS650 guy, so I am sure he ships abroad. http://www.mikesxs.com/mikesxs-electrical.php?category_id=2.1
His wires are good, also, if you need them. If you still have the original wires, DO NOT throw them away if you replace them. You want to remove the ends that plug into the coil with a soldering iron, and reuse them with the new wires. Continue to do this. This type of connection is far superior to the crimp-on type.
I don't know if the later bikes were plagued with the crack-o-matic coils or not.
Also, you may have a good spark in atmosphere, but not under compression. That is not a perfect test.
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fwww.mikesxs.com%2Fparts%2Fimg250%2F23-3113.jpg&hash=884d7c12d6e11ee0241fc1d868be3ab3fb2fc05d)
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ok thanks rob and eyeryone ithink i will switch the plugs leads and caps and i will let you know how it goes