Finally………………………..I fixed the Beta, the phantom electrical problem turned out to be the stator (known KTM weak point)… but it was reading as within spec on the ohm meter so I tested everything else 9 times over, but in the end I just could not see what else it could be…. I did the rewind myself (to save a few quid) and it is working nicely. Thank feck.
The bike just stopped one rainy Saturday as i was off trying to get some tyres, I pushed it to a service station (quite nice as it was 1deg that day and i was freezing) … petrol OK so i checked the spark…Nothing!!
OK- i assumed it was salty water in a connector block so i took the tank off and tried to find the short at he side of the petrol station, using some stuff from the garage, ie cotton buds, a nail file, distilled water, petrol and the air hose I had a go and tried to clean up the muddy oily connections and blocks… two hours later, when i was sure i had cleaned ever wire possible, tested the kill switch and the plug and looked at the HT leads and cap and kicked it over about 3000 times… I had to call the RAC, some hours later they did the same things again and looked at the HT coil with his multi meter but after an hour he gave up and called the tow truck to come and get the bike home… I got home at 10.30 and i was massively pissed off and so cold, my balls pulled themselves up somewhere inside my belly, it took 50 mins in a hot bath to get my scrote feeling normal…
Had to leave the bike a few weeks after that as I was too depressed to look at it and busy as feck with other stuff (and it was too cold to work on the bike outside again). the remaining culprits were the CDI (timing brain) it is a black box that can’t be tested with out a fancy computer or a working bike, the HT coil, the plug cap, a bad earth, and the stator coils…. over the coming weeks I tested everything and one by one they all checked out as fine!
KTM stators have 3 coils, the main one gives voltage to the lights etc, as the Beta can work without a battery this one was not part of the problem, the next one is the exciter coil this provides the spark with it’s energy, the final coil is called a pulser it tells the CDI’s when top dead center is so it can get the timing right, these go most regularly. KTM suggest two tests in the service manual 1) resistance 2) peak voltage (which needs a fancy meter) these are the resistance readings for the 3 coils, the order is exciter coil, pluser coil and the primary winding….
they are all about right, +-10% so I did not think there was reason to look any further at these coils… so I spent the next two free weekends taking the other components and testing them in working bikes… and damn it they all worked fine!!!
after a lot of testing of componets, i decided it must be the stator exciter coil that was giving me the problem…somewhere in that cump of tightly coiled fine wire was a short, where the wire had rubbed though the lacquer put on it, or maybe the oil in the bike had dissolved it away, the point was that only some of the turns were working, feeding the CDI and HT coil with too low a voltage to make a spark. Or at least that was my best guess.
it looks like this: first i had to remove the old windings, cutting the old wire back was a pain as it is set in resin. also i could not get any tec spec on how many turns of wire are on the standard stator, so i was counting on being able to count down the turns as i took the with wire off… this was risky as I needed to know the number exactly and in the end did not work out as planned…
in the end i got them off..and as i say took a shot that there might be about 600 turns on it..
i bought this special hi temp wire from a place in Essex, it is slightly thicker than the original and much better quality. The main difference is the original winding is done by a big sort of lathe that moves the stator around gradually as well as spinning it and keeps even tension on the wire but not so much as to snap it… i made a widget from an old pen and kept my finger on the end as i was winding it on, to keep the wire tight… I started at the bottom and wound to the top gently and then back again, counting each turn.. 566, 567,568,569,560,561,562.. it took ages and if you put on a single slack wind you can bet it will vibrate like feck down there right in the motor and wear off the wires clear insulation in 30 miles!
as my flywheel magnets are 5 years old, i guess they must have lost some uoomph, so as well as fatter wire i put on a few extra turns, in the end i put 777 turns (like to guess my lucky number anyone?)
it looked like this:
i got some special epoxy resin from maplin online that is made for toy electric race car winding motors, it can stand 250 degrees C and has almost no conductivity, also it is quite runny and so gets nice and deep in the windings in case i have a few loose windings, that would like to vibrate off their laquer and short out again. it comes in a single use packet with a clip in the middle, keeping the harderner at one end, pull off the clip mush it about then cut off a corner and apply, i had to keep turning it over untill it set, so it did not all run onto one side. All in all took about two hours to go thick.
I put a bit of extra sealant on the wires of the primary winding as i managed to scratch them a tiny bit taking the old wire off and needed to cover it..
Al ready to rock…Makes a brighter fatter spark now, the CDI seems fine (though i might cook it with too many volts), started with the slightest kick….. took it for a glory ride and it is much smother low down, and the tendency to stall at low RPM, with anything other that a brand new plug seems gone.
Conclusion: Total cost £2.50 for the wire and £3.15 for the fancy Resin, new KTM stators are around the £200 so might be worth the evening in… if she holds….
tags: Beta 450 RR diy stator coil rewind, KTM exc stator coil self wind, exciter coil repair.
Thanks to everyone I spoke to on the phone about my problem, and thanks to Simon who was very cool letting me test an unknown coil on his lovely working bike, gnome, lady gnome, and the brilliant trail world mechanic who were all stars lending me a working beta for some readings and a CDi swap, and big thanks to Portuguese David and his dad Jeorge for taking the CDI to work to test it and for calling me every weekend and verbally kicking me up the arse when i was too depressed to even watch a motoGP. Finally a big thanks to the guy that invented Google… for making it possible to find any information on any subject, some specialist winding wire and hi temp resin all from my desk, cool as feck.
If all this seems a bit too much work… westcountry windings of Harlow, Essex (go figure?) http://www.westcountrywindings.co.uk/applications.htm do a proper rewinding service for about £80 and they will rewind the main coils for brighter lights for an extra tenner too! They are top blokes and that’s what I will be doing if/when my home spun deluxo do-it-yer-self job shakes itself apart.
Still after 4.5 months off road, when I finally put it back together (with no other way of testing it or even knowing for sure if it that was the real problem)… that first sight of a big blue spark! Satisfaction