AllanB Posted March 12, 2014 Author Share Posted March 12, 2014 This problem does run on a bit, yet another disappointment. Took the clutch cover panel off, expecting to find one of the triggers loose, given the recent symptoms of down to firing on one cylinder and found nothing untoward. I little bit of dirt on both triggers, but checking out the resistances both measure 43ohms. I assume that if we get the same reading all is well, anyone know a better way to test then before I reassemble? The digital tacho still hasn't arrived from China and that will help us a lot, meanwhile we are thinking a sticky float chamber valve, as one float chamber has much more fuel than the other. We are thinking that the misfire could be caused by number 2 cylinder flooding and drowning the sparks. Really ? Like one hundred posts back I asked for photos of the plugs and you couldn't do it but said they were OK. No no, this total failure of cylinder two and the wet plugs only happened last week and suddenly. That is why I suspected a trigger problem, after I had eliminated, plugs, coils and CDIs as a possible cause. Link to comment Share on other sites More sharing options...
AllanB Posted March 19, 2014 Author Share Posted March 19, 2014 So have I finally got to the bottom of this misfire problem? I think so. The rest of the bike was/is by no means perfect, after all it is 30 years old and maintained in Thailand, but I am pretty sure now that the main culprit has been one of the float chamber valves. It was certainly the reason for the latest total cylinder failure, as it had jammed open and was flooding cylinder 2. The excess fuel found it's way into the sump, after I converted a leaky vacuum operated petcock into a manual one and then left the fuel on. When I measured the height of the two floats (after I had cleaned up both seats) there was about 1mm difference between the two and then I found the correct setting height was 7mm. Cylinder 2 was set at around 6mm, so I adjusted it back to 7 and reassembled the rest of the bike, after doing a recheck. Now it revs right up to 9,000rpm with only a very slight hiccup, but nothing compared to what it was before and since I never rev much beyond 4k, it isn't an issue. So something quite minor really, but 6 months to get to the bottom of it, if it is fixed, what do I do now? Well there are a couple of small oil leaks, one that was existing and another I created when I was unable to renew an engine gasket. Still, just bought a new box of cornflakes, so that is the next little job. The exhaust i still popping a bit, which is nice but may get on my nerves and the air filter still isn't standard. But anyway thanks to all those who helped and I now know the bike a little better.... PS. I may look around for two new float chamber valves and seats, as the existing ones are not perfect and will run the bike on Benzine, as the gasohol may have been responsible for the damage. Link to comment Share on other sites More sharing options...
VocalNeal Posted March 19, 2014 Share Posted March 19, 2014 I love a happy ending. Link to comment Share on other sites More sharing options...
AllanB Posted March 19, 2014 Author Share Posted March 19, 2014 I like reading about how others fixed faults on their bike, unfortunately mine was a bit tedious, yes that was an understatement. I guess one lesson I learned was to be meticulous when it comes to carb cleaning, checking and setting up, then maybe I would have noticed the float levels, only 1 mm out but enough to cause a slight overflow and gasahol doesn't do carbs any favours either. Leaves a brown stain over everything, the "Bismark" of fuels then. Link to comment Share on other sites More sharing options...
ll2 Posted March 19, 2014 Share Posted March 19, 2014 so no more stator readings? i am sad. Link to comment Share on other sites More sharing options...
paz Posted March 19, 2014 Share Posted March 19, 2014 Glad to know you got it fixed and that I was wrong in saying it was an electrical fault. I would also have said that float off by 1mm could not have caused this, but hey facts are what they are. Link to comment Share on other sites More sharing options...
seedy Posted March 19, 2014 Share Posted March 19, 2014 Congrats. Glad it is fixed. Tedious at times, but it did not defeat you. Kudos !! Link to comment Share on other sites More sharing options...
AllanB Posted March 19, 2014 Author Share Posted March 19, 2014 To be honest most people including me were convinced it was electrical, almost from the start. All the symptoms led to coils and with the small performance improvements along the way there were quite a few peripheral faults, or certainly faults that would have shown themselves in the future. Incidentally a few people have said CDI's either work or they don't, which is often true of electronics and I never discovered any way of testing them, or indeed fixing them. Also, I don't understand why they are powered by a variable AC supply from the stator and not a stable DC supply from the battery, perhaps someone could explain in simple terms. Or do I have this totally wrong. 1 Link to comment Share on other sites More sharing options...
seedy Posted March 19, 2014 Share Posted March 19, 2014 Also, I don't understand why they are powered by a variable AC supply from the stator and not a stable DC supply from the battery, perhaps someone could explain in simple terms. Or do I have this totally wrong. Don't know your bike, but most use alternator to provide AC because they are lighter and smaller. The old DC generators were quite large and heavy. There is a rectifier in the circuit to change AC to DC to run the bike. Link to comment Share on other sites More sharing options...
AllanB Posted March 20, 2014 Author Share Posted March 20, 2014 Also, I don't understand why they are powered by a variable AC supply from the stator and not a stable DC supply from the battery, perhaps someone could explain in simple terms. Or do I have this totally wrong. Don't know your bike, but most use alternator to provide AC because they are lighter and smaller. The old DC generators were quite large and heavy. There is a rectifier in the circuit to change AC to DC to run the bike. Yes, the stator/rotor is an alternator supplying AC current, but is variable in it's output and therefore not good for powering electronic equipment....... Oh! sorry I have just thought of the answer... Coils. which are transformers only work on AC,... so I assume they use 12vdc to power the electronics and then pass on the AC power signal, to the coils to up the voltage. So am I right in assuming that the rectifier plays no direct part in firing the engine? Link to comment Share on other sites More sharing options...
yankee99 Posted March 20, 2014 Share Posted March 20, 2014 All the coils on my bikes are based on DC and work after the regulators. Not old like yours but my cars with a points distributor in the 70s also fired the coils with DC. Link to comment Share on other sites More sharing options...
VocalNeal Posted March 20, 2014 Share Posted March 20, 2014 Many older bikes ran their headlights off AC from the generator. Link to comment Share on other sites More sharing options...
yankee99 Posted March 20, 2014 Share Posted March 20, 2014 Many older bikes ran their headlights off AC from the generator. Yes but the bike in question is not that old and its Japanese. Of course I havent seen a schematic. My memory isn't great but I think my Honda 350 standard 12volts Link to comment Share on other sites More sharing options...
AllanB Posted March 20, 2014 Author Share Posted March 20, 2014 Seems I got it completely wrong, should have known better. Bloody Chang beer, knew I should have stuck with Archer. Now I am confused, why is the CDI powered from the stator/rotor and not direct from the battery? Link to comment Share on other sites More sharing options...
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