tltel Posted December 30, 2012 Report Share Posted December 30, 2012 Hi Matt Interesting reading, nice looking bike. I am not familiar with these carbs, but have you checked that the float hieght is set right, you should be able to get the infomation on here or google it. It usually involves bending the tab on the float that shuts off the fuel flow, i see from your picture that the carb is tilted down towards the engine, so if fuel level is slightly too high then it could be flooding the engine but not coming out of the carb overflow. Also what fuel oil mix are you using? not sure whats recomended for these bikes but its worth checking your not putting too much oil in! I would also be checking head bolts are tight, (can need tightening after a rebuild) and take off exhaust and shine a light in the port have a look at piston and bore, you dont know that the rebuild was done by someone that knew what they were doing. ( i bought a bike and found that it had only one piston ring in it once) did you check out the crank seal when you took the flywheel off? good luck TLTEL Quote Link to comment Share on other sites More sharing options...
zerorev3rev4 Posted December 30, 2012 Report Share Posted December 30, 2012 I managed to snap this one for you mate. She's a bit dirty around the engine but that's what they're made for! This is a great idea. (Today I couldn't even start the engine besides one kick where she splutter for ten seconds before dropping out and dying.) So, I connected up my timing strobe with the plug out but earthed with a piece of wire. I got multiple fast flashes every time when spinning the engine over by hand. (Which was relatively easy with the plug out.) When the plug was back in though the strobe would only flash briefly once every other kick or so. So I think some of you may be right about the plug failing inside the cylinder. In the morning I'm going to repeat my strobe experiment and if I get the same results I'm going to remove the carb and repeat. If I can confirm that the spark is failing inside the cylinder even with the carb disconnected then it is the compression that's snubbing out a weak spark. If by some chance the plug does fire properly inside the cylinder without the carb then I can investigate a potential problem with fuelling/ flooding and fouling of the plug. It's fascinating because the motorcycle works by running multiple independent systems which must all harmonise and work together to produce a functioning engine. Ignition, air and fuel for example. In my case each one of these systems is working correctly when independently inspected. They are all observed to function but that synergy is not happening. When combined, these systems are not harmonising to produce the desired result. A bit of mystery and a bit of fun in the workshop. I guess this is what I signed up for and this is what I get. ...If the plug fails tomorrow under compression with the carb off then I'll finally try a new coil. Here's hoping. Thanks again. i think you could be on the right track now i would of sugested this method earlier but thought someone else would of ,, it has a weak spark which is breaking down when hot when engine is running it runs ok due to plenty voltage been created ,but at kicking speed it cant generate enough so it cant ignite the fuel hence more you kick more it floods and wipes out the spark even more ,this could be due to a bad earth ,bad stator coil points or condensor or a wire arking out to earth (the one to the coil ) it can be rubbing on the stator or even the flywheel ,it could also be the hi tension coil the leed cap or plug , if plug new ( unused not fairly new as will not be much good after been flooded so many times ) i would check routing of wires from points and that they are insulated on the pivot and the contacts are clean , i would also remove the condensor from stator and fit an old car mini type one nearer the coil away from engine heat Quote Link to comment Share on other sites More sharing options...
woody Posted December 31, 2012 Report Share Posted December 31, 2012 i think you could be on the right track now i would of sugested this method earlier but thought someone else would of ,, it has a weak spark which is breaking down when hot when engine is running it runs ok due to plenty voltage been created ,but at kicking speed it cant generate enough so it cant ignite the fuel hence more you kick more it floods and wipes out the spark even more I did, I suggested this about a week ago, along with eliminating the kill button as a possible cause (it probably isn't but for £12 - 15 I'd have replaced it anyway, or at the very least disconnected it. But focus went back onto the carb. If fuel is left on whilst the engine isn't running and the carb floods, it will pour fuel out of the overflow and it can also run down the inlet and fill the crankcase (and I mean fill it, you won't believe the mess when you eventually get the bike started and it burns off whatever is left after kicking with the spark plug out) If the carb floods whilst the engine is running it will still pour fuel out of the overflow but the engine will also run very poorly due to over fueling, probably 4-stroking at best, like running with the choke on when the engine is warm. None of these symptoms have been reported which is why I suggested eliminate the electrics first. When the bike is running it runs fine so it's very unlikely anything is wrong with float levels, timing, jetting, fuel/oil mixture, crank seals etc. Quote Link to comment Share on other sites More sharing options...
handmadematt Posted January 1, 2013 Author Report Share Posted January 1, 2013 SOLVED. Thank you everyone, really - So much thanks! It was the coil. I changed it for a new one and she literally starts first kick in any situation... An absolute joy. I appreciate that many of you said this straight away and I've investigated all sorts of other avenues but there is nothing lost, it's been an important journey for me and has resulted in me being fully acquainted with the bike, inside and out... She feels like an old friend already. What a valuable resource this forum is, thanks for making it what it is. Speak soon. Matt 2 Quote Link to comment Share on other sites More sharing options...
lineaway Posted January 2, 2013 Report Share Posted January 2, 2013 I`m glad you are happy. You should go back to woody`s posts. Coils rarely go out. I would re-think your ground. Either way have FUN! Quote Link to comment Share on other sites More sharing options...
handmadematt Posted January 2, 2013 Author Report Share Posted January 2, 2013 (edited) I don't think there is a grounding issue. When I fitted the new HT coil the engine started nicely, to confirm that it wasn't just coincidence I then swapped it back for the old one and I couldn't start the bike, re-fitted the new one and then hey presto. An interesting thing came up in regards to the ground though. When I was looking in the magneto case behind the flywheel checking if everything was OK I discovered that one of the magneto coils (of which there are three) had it's earth (green wire) cut and hanging loose. The other end of the green wire that ran all the way up to the HT coil was earthed to the engine case behind the flywheel here. I traced this up to the HT coil and it was earthed to the HT coil mounting point... So the previous owner has had the HT coil earthed twice, once here with this green wire and again with an addition of a black wire that runs down the inside of the frame (inside the riders leg) and bolts to the engine case above the drive sprocket. I confirmed this by disconnecting the black wire and I still got a spark. So, having discovered this I had previously thought.. "Ah, with one magneto coil out of service maybe that is my problem." So I had already re-connected that to the same earth that the green wire was already on inside the magneto case. It did not solve my problem unfortunately. Maybe this "third" magneto coil is only for auxiliary lighting or something? Is it not part of the ignition? The bike clearly ran before without it... Unless that's what caused the HT coil to fail? A contestant under powering from the magneto? (Seems unlikely to me.) Anyway, it's all working now. Cheers. Edited January 2, 2013 by handmadematt Quote Link to comment Share on other sites More sharing options...
feetupfun Posted January 2, 2013 Report Share Posted January 2, 2013 (edited) I don't think there is a grounding issue. When I fitted the new HT coil the engine started nicely, to confirm that it wasn't just coincidence I then swapped it back for the old one and I couldn't start the bike, re-fitted the new one and then hey presto. An interesting thing came up in regards to the ground though. When I was looking in the magneto case behind the flywheel checking if everything was OK I discovered that one of the magneto coils (of which there are three) had it's earth (green wire) cut and hanging loose. The other end of the green wire that ran all the way up to the HT coil was earthed to the engine case behind the flywheel here. I traced this up to the HT coil and it was earthed to the HT coil mounting point... So the previous owner has had the HT coil earthed twice, once here with this green wire and again with an addition of a black wire that runs down the inside of the frame (inside the riders leg) and bolts to the engine case above the drive sprocket. I confirmed this by disconnecting the black wire and I still got a spark. So, having discovered this I had previously thought.. "Ah, with one magneto coil out of service maybe that is my problem." So I had already re-connected that to the same earth that the green wire was already on inside the magneto case. It did not solve my problem unfortunately. Maybe this "third" magneto coil is only for auxiliary lighting or something? Is it not part of the ignition? The bike clearly ran before without it... Unless that's what caused the HT coil to fail? A contestant under powering from the magneto? (Seems unlikely to me.) Anyway, it's all working now. Cheers. Sometimes people run an earth wire all the way from the stator backing plate to where the HT coil attaches.to the frame. This avoids any concerns about the resistance of the connection between the backing plate to the inner case, the engine mounts to the frame, and the frame to the coil. Sometimes that same earth wire is also run to the kill switch to avoid passing a current through the steering head ball races when the kill switch is operated. That current can cause damage to the bearing surfaces. Having an earth wire run to the kill switch also makes the kill switch more reliable for stopping the motor. The third stator coil is probably for lighting/battery charging. Some bikes have two or more lighting coils on the one core and others have two separate stator coils for the lighting. Bikes with points/flywheel magneto ignition usually only have one (stator) ignition coil. Edited January 2, 2013 by feetupfun Quote Link to comment Share on other sites More sharing options...
guys Posted January 2, 2013 Report Share Posted January 2, 2013 I`m glad you are happy. You should go back to woody`s posts. Coils rarely go out. I would re-think your ground. Either way have FUN! Maybe coils do rarely go out, but somtimes they do. On my BMW Boxer the coil had an almost invisable crack and only when the engine was warm, the coil would fail because the engine heat would expand the coil a litlle bit, open the crack a bit and the engine would run bad or stop completely. When I let the engine cool down the coil would work again... Quote Link to comment Share on other sites More sharing options...
lineaway Posted January 3, 2013 Report Share Posted January 3, 2013 Guys , if you followed this post he answered the question straight away. He had a single earth wire instead of the frame as the earth. It was possible that changing out the coil would change to a good ground. The owner `proved` to himself all was good. Which is what he needed to do. People always try to buy coils to fix the problems they don`t understand. I worked in a shop for years and saw this time and time again. I`ve only ridden trials for more than 40 years, and would not send someone to `spend` instead of repair. This would have been the third coil in a short time period according to the past owner. Quote Link to comment Share on other sites More sharing options...
handmadematt Posted January 3, 2013 Author Report Share Posted January 3, 2013 It was possible that changing out the coil would change to a good ground. I don't think there is a grounding issue. When I fitted the new HT coil the engine started nicely, to confirm that it wasn't just coincidence I then swapped it back for the old one and I couldn't start the bike, re-fitted the new one and then hey presto. An interesting thing came up in regards to the ground though. When I was looking in the magneto case behind the flywheel checking if everything was OK I discovered that one of the magneto coils (of which there are three) had it's earth (green wire) cut and hanging loose. The other end of the green wire that ran all the way up to the HT coil was earthed to the engine case behind the flywheel here. I traced this up to the HT coil and it was earthed to the HT coil mounting point... So the previous owner has had the HT coil earthed twice, once here with this green wire and again with an addition of a black wire that runs down the inside of the frame (inside the riders leg) and bolts to the engine case above the drive sprocket. I confirmed this by disconnecting the black wire and I still got a spark. So, having discovered this I had previously thought.. "Ah, with one magneto coil out of service maybe that is my problem." So I had already re-connected that to the same earth that the green wire was already on inside the magneto case. It did not solve my problem unfortunately. Maybe this "third" magneto coil is only for auxiliary lighting or something? Is it not part of the ignition? The bike clearly ran before without it... Unless that's what caused the HT coil to fail? A contestant under powering from the magneto? (Seems unlikely to me.) Anyway, it's all working now. Cheers. Thanks for the contribution mate. All the best. Quote Link to comment Share on other sites More sharing options...
guys Posted January 3, 2013 Report Share Posted January 3, 2013 Lineaway, I can't say with certainty what the problem was with Handemadematt's bike sitting behind my PC. I was only saying that coils do fail sometimes. 1 Quote Link to comment Share on other sites More sharing options...
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