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Old 08-06-2013, 09:49 AM   #1
BlkNH750 OP
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Joined: Aug 2013
Oddometer: 2
Anybody to help with '75 Dt250 ignition issues?

I have had this bike for almost two years now and haven't had the chance until recently to pay the correct amount of attention to it. The first goal is to get it running reliably and then to work out the remainder of the kinks. I am mechanically able, but I am more familiar with newer bikes and their electrical systems.

This bike has been unfortunately been through a lot, and it has been stripped to a dirt-only state. It retains the stock Mitsubishi magneto system, and had been wired directly to a kill switch. I was able to acquire an additional stator plate and coils for it.

This is what I have done so far:
1. Replaced (frame mounted) primary ignition coil with new Yamaha unit
2. Replaced points and condenser with spec'd mitsu units
3. Set point gap to .012" @3.2mm BTDC as required for timing.
4. Checked resistance of source coil = .6 ohms
5. Good grounds to all electrical components

But..
1. I cannot get more than 2.8 VAC from source coil when kicked
2. I find that output from primary coil maxes at 18.6 VAC



I completely stumped beyond what I have done so far and I need to reach out for help. I am looking forward to getting this bike running good if I could only get spark


..Thanks in advance

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Old 08-07-2013, 01:44 AM   #2
Twin-shocker
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You firstly need to check the resistance figures you have with those in the shop manual, or compare with those of spare stator. Flywheel magneto systems are generally very reliable, so if your resistance figures are ok, I would suggest very carefully check of the installation of the new points, and if you have fitted pattern parts, that they may well be faulty from new.

Its also worth checking if the new HT coil you have fitted is the correct one for the bike, as these do vary and while it might appear identical, may be quite different. Finally always worth disconnecting the kill switch, and fitting new spark plug, and non resistor type spark plug cap.
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Old 08-07-2013, 07:15 AM   #3
BlkNH750 OP
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From what I can see, the measured impedance of the source coil, and the ignition coil match what is listed in the Clymer manual. Whereas the Clymer is not the most comprehensive manual, it does list the resistance values for each of the components tested.

The ignition coil that is on the bike is NOS for the Dt250 of this year, and was tested on a friend's Dt250 to check for functionality. The bike is currently without a kill switch of any sort, because I wanted to eliminate that as possible problem area. I am currently running a single wire from the stator to the ignition coil.

I have tried three spark plugs that match what would have come stock on the bike, and have tested 2 different types of plug caps. I am running out of ideas... mainly because I have exhausted all of the ones that have been suggested or read about.

Any additional help would be greatly appreciated.
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Old 08-07-2013, 08:03 AM   #4
Foot dragger
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Location: chico,just below rag dump(nor-cal)
Oddometer: 12,818
It looks to have had a rough time.

I do have a complete engine for one of those sitting in a box here,its has compression but I know nothing more about it.
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Old 08-08-2013, 01:50 AM   #5
Twin-shocker
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Quote:
Originally Posted by BlkNH750 View Post
From what I can see, the measured impedance of the source coil, and the ignition coil match what is listed in the Clymer manual. Whereas the Clymer is not the most comprehensive manual, it does list the resistance values for each of the components tested.

The ignition coil that is on the bike is NOS for the Dt250 of this year, and was tested on a friend's Dt250 to check for functionality. The bike is currently without a kill switch of any sort, because I wanted to eliminate that as possible problem area. I am currently running a single wire from the stator to the ignition coil.

I have tried three spark plugs that match what would have come stock on the bike, and have tested 2 different types of plug caps. I am running out of ideas... mainly because I have exhausted all of the ones that have been suggested or read about.

Any additional help would be greatly appreciated.

If the resistance figures are good, then the problem is related to either points/condenser or the wiring. Did you carefully check the installation of the points as I suggested, and is all the wiring good?
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