Airhead

Dont assume anything! If the coil has been bashed with something sharp it will cut the insulation cover and possibly the winding too. My main concern is the pulse coil as thay are expensive and very hard to come by. The other one is available as a non yamaha replacement at a good price. I want you to be very careful, examine each coil you will see how one side is grounded under a mounting screw. if needs must you will have to remove the coils to check this tab is attached to a ciol winding. The trouble is if someone wasnt careful and omitted the washer that sits under the screw...then this tab could twist as the screw was tightened and snap free of the winding.

ok you get to remove the rotor and stator again, you need to make sure that the coils are grounded at one side properly and connected securely to their respective coloured wire.

right now make sure that you are not on the 200 Ohm range when you do the brown wire, you are expecting 430 Ohms here so you need to be on the 2K Ohm range. 200 Ohm range is fine for the red/white one though. At least we know the black is properly grounded. check again

Right you need to clarify something you said. "The plot thickens (Or gets clearer ) I don't seem to be getting any resistance between both of the two you told me to check." Does this mean you are seeing a dead short just like holding the two test probes together.......or.....does it mean you are not seeing any value of resistance, just like holding the probes in thin air?? That comment of yours can be taken either way..try to be clearer, like open circuit or short circuit

Yes you are checking correctly. The black wire is connected to the baseplate so double check now from the two coloured wires to a clean part of an engine screw, and from the black wire to an engine screw (this should be a dead short obviously)

Check the resistance of the magneto stator coils Pulser white/red to black = 12.4 Ohm +- 10% Source coil, Brown to black = 420 Ohm +- 10%

Are you using the choke? It wont start without it unless the engine is warm. It is lever up for choke on mine, not sure about yours though, whether the carb is the same or not.

You wont see any voltage on the black wire, this is because the black wire is connected to the backplate and so is grounded. Remember I marked it on your picture in post #6 You must understand that there is no way of checking the CDI function and so what you have to do is check everything else and when happy...replace the CDI. We havent checked everything yet though. you need to connect the black back up to the CDI did you ground the ignition coil mounting to the common ground? Wired like this?

Was the two stroke oil run dry? If so you will need to bleed the pump before using the engine as it may be airlocked.

Happy birthday Drewpy,

my latest DT came with only one set of keys, I just took em along to a locksmiths and now I have two, this means that if I lose one I am still good to go Wise beyond my years

I remembered reading it a while back I suggest you ask on yamahait.au these bikes are popular in australia

Bob, read this and see if you think it applies to you. From another forum http://www.bikechatforums.com/viewtopic.php?t=163786&postdays=0&postorder=asc&highlight=dt175mx&start=100 I know its about a 175 but I doubt that matters.

No poit in guessing until the exhaust is fixed and sealed properly.

Just read it more closely, no it's not for CDI models This is though and is even cheaper http://cgi.ebay.co.uk/Yamaha-DT125-DT175-DT250-DT400-New-Ignition-Coil-QC125-/310191454436?cmd=ViewItem&pt=UK_Motorcycle_Parts&hash=item4838d9f8e4 Dont beat me up though if it still dont work, I can only do so so much on a qwerty keyboard,

0.12 Ohms...that sound like a dead short to ground. I bet you get that reading by holding both meter leads together. New coil £13 including delivery Yambits coil for DT175

have you put the floats in upside down? I suspect the little pegs that operate the float arm are not moulded exactly central to the float diameter.

Pattern coils are not all that expensive Just do a search for one, I guess you are American, here in the uk for example http://www.wemoto.com/bikes/Yamaha/DT_175_MX/78-79/picture/Ignition_Coil/'>http://www.wemoto.com/bikes/Yamaha/DT_175_MX/78-79/picture/Ignition_Coil/ http://www.wemoto.com/bikes/Yamaha/DT_175_MX/78-79/ £16.45 You will also probably fetch a better price for a runner If the coil is scrap as it stands now...why not have a go at digging out the lead from it and replacing that with some new lead...nothing to loose there just check you get the 5900 ohms or whatever before you buy new lead.

Sounds like 1: A blocked main jet or 2: You are taking the choke off too early. Check sparkplug gap.

Bob, how can you get an answer when you dont fill in the detail What bike model what year engine frame numbers? I cant guarantee any answers but info will help anyone who may try to help.

Aahh tickover sticks I thought it was a new carb adjusting tool you had there. Welcome celicatintin

If your'e not happy with the connections, neither am I. It goes without saying the all need to be clean and sound, as in no oily wires twisted together. More things to check Check the resistance values of your magneto source coil = 420 ohms +- 10%............Brown to chassis Check the resistance of the magneto pulse coil = 12.4 ohms +- 10%...........White / Red to chassis Check the resistance values of the ignition coil, Primary = 1.0 ohm =- 15%, secondary = 5900 ohms +- 20% But sort the wiring first.

Thats how it is on the bike, the bolt alone isnt trusted and a wire is placed under it. I do understand your scepticism but you are not in a position to cast doubt.

When on a standard bike, there is a ring terminal under the HT coil mounting bolt, with Bk wire to chassis.

Make sure the HT coil mounting bolt is clean and has a wire to the same chassis common point.