vambo Posted May 23, 2009 Author Share Posted May 23, 2009 A weak spark can give the impresion of a rich mixture as the spark struggles to ignite the fuel so it doesent burn properly and soots up the top end. Leaning the mixture out will help it run but ultimately at higher rpm you will lose out. see that's why i've always had brit bikes before. magneto's work or they dont and you can set the timing with a piece of fag paper and a stick (i'm not joking either, that's exactly how i set it on the Matchless) :-) Link to comment Share on other sites More sharing options...
vambo Posted May 25, 2009 Author Share Posted May 25, 2009 Ok Just been out to the bike. There are 4 wires and here are the readings. The readings where jumping around a bit but that could be my meter. white/red to black 12.4 (peaked at just under 14 at one point) brown to black 413 red to black 15.9 (peaked at 18) so does that tell us anything ? petrol and match on standby Link to comment Share on other sites More sharing options...
Moderator Airhead Posted May 25, 2009 Moderator Share Posted May 25, 2009 Ok Just been out to the bike. There are 4 wires and here are the readings. The readings where jumping around a bit but that could be my meter. white/red to black 12.4 (peaked at just under 14 at one point) brown to black 413 red to black 15.9 (peaked at 18) so does that tell us anything ? petrol and match on standby The figures should be Source coil 1 brown_black + 420 Ohms Source coil 2 Red_Black = 13.6 Ohms Pulse coil Wht/Rd_Black = 12.4 Ohms All Plus / Minus 10% so it looks like your source coil 2 is out of spec, thats the thin one piggy backed onto the other, check this one again to make sure you didnt have a bad connection. Link to comment Share on other sites More sharing options...
bzurborg Posted May 27, 2009 Share Posted May 27, 2009 Sorry to butt in but I have been following this thread because I am having the same problem with my Yamaha RT100 - It will bogg down after it starts and when you give it throttle it will eventually die. What about the oil to gas mixture would that cause this problem - My model has an oil injector on it -Just wondering if that could be the issue with yours as well. What about a bad reed valve. Any input on these two particular issues would be great thanks Brian Link to comment Share on other sites More sharing options...
Moderator Cynic Posted May 27, 2009 Moderator Share Posted May 27, 2009 The figures should be Source coil 1 brown_black + 420 Ohms Source coil 2 Red_Black = 13.6 Ohms Pulse coil Wht/Rd_Black = 12.4 Ohms All Plus / Minus 10% so it looks like your source coil 2 is out of spec, thats the thin one piggy backed onto the other, check this one again to make sure you didnt have a bad connection. That is the coil that deals with high rpm realistically from around 3000rmp upwards. Link to comment Share on other sites More sharing options...
vambo Posted May 27, 2009 Author Share Posted May 27, 2009 finally got out to the bike. I've taken the unit out and rechecked the readings on the actual coils. (put a new battery in the meter too just in case) source coil 2 is still way over spec and still reads 15.9 white/red to black 12.4 brown to black 413 red to black 15.9 now questions are what would happen given coil 2 is way over spec? if its mullered where would be a good place to get a new one or is it worth trying to get it re-wound? i got the part number from the DT175F parts catalogue as 2A7-85512-20-00. Brian re your questions. I'm sure the more experienced guys here would have an answer but my guess would be if it was oil/gas mixture you could tell by the amount of smoke she kicks out, plus the plug would be very oily (mine is neither oily or sooty just black) and as far as the reed goes if there not stuck or split i don't think they can make much difference. I've not taken mine off but i can feel when the carb has been off and its not stuck and there's no feel of damage Link to comment Share on other sites More sharing options...
Moderator Airhead Posted May 27, 2009 Moderator Share Posted May 27, 2009 you can get a coil from Yamaha but will cost loads and to be honest I dont think its that or worth spending silly money on it yet, you can also get a coil from electrex world, source coil 1 and 2 will cost a mere £44 posted . Ive just bought me a set but source coil 2 is high at 15.3 ohms (out of spec) and source coil 1 is low at 388 ohms (in spec though), so you can see why it isnt something to rush into, I honestly dont know how much it matters either. Options to consider are Try it with the air filter removed. Does it need a de-coke, is the exhaust port getting made up? is the expansion pipe free flowing, try the vacuum cleaner test, seal the vacuum cleaner against the manifold, you should not get a huge difference in tone, if you do it indicates blockages within. Have you tried a new spark plug? Pressure test your engine (see my topic "pressure testing") Alternatively, place the crankcase breather in a jar of water, run the bike and rev it, watch for bubbles, Then remove the oil filler cap and does it smell of fuel? ...Note The bubble test wont be effective while this filler cap is out! this is a crude test of the RH crank seal. With engine running spray WD40 through the gaps in the flywheel aim at the LH crank seal, listen for a change in engine sound / speed, this is a crude test of the LH crank seal Do an engine compression test, not the same as above, unless you can feel lots of compression through the kick starter. Check your ignition timing, the true test is static using a dial gauge and stand, however you could do it with a strobe lamp if you power the strobe from a 12v battery At this stage you may as well look at the HT coil readings too, primary 1.0 ohm...15%, secondary 5.9k ohm...20% These tests will check the general health of your engine with little cost Link to comment Share on other sites More sharing options...
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