Vintage Dirt Bike Q & A

I have replaced the points with new ones, new plug, replaced old pieced together ignition coil with a new one and a new condensor.
I am getting erratic and infrequent spark to the plug.
Did the following test per the Clymer manual;
Tried to set the timing with a 6 volt battery and test lite....FAILED! lite never went off.
Next i disconnected the two wires to the points and tested for continuity between base plate and where the wires connect to the points...open no continuity.(fly wheel off)
when i connected the wires back to the points i have continuity with points open and closed.
Could this be caused by a bad coil on the stator????
I can't seem to find any thing that tells me how to test it....when i read the AC volts from the stator while kicking it over i read between 10 and 20 volts AC.
Anyone know what is up with this????

Sounds to me like it could be a bad stator coil. Try reading the coil resistance (across the open points) and see what you get. I read 2.9 ohms on mine, but I don't know if that's correct or not.

A guy on eBay a while back was having similar symptoms with a non-running MR175 he was trying to sell. He replaced the stator, and boom - the bike came back to life.

Ray

_________________
'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

thanks for the quick reply...i think it is the stator too.
reading across the points open was 3.0 ohms open and .8 Ohms closed.
I have a used stator coming that i bought on ebay...it is the only thing i have not replaced.

Let me see if I can help. I know everything is new but sometimes its the little things that count. So use what you want from the following,,,,,,,

1) Check the continuity from the points to the coil, There is a inline connector between the wires on the stator and the coil. Its usually located near or just below the air cleaner box tied to the frame. BeIts not a good connector,,,,,so carefully examine it. If its loose or has has any corrosion on it your spark suffers greatly. To check to see if its the connector, pull it apart and check continuity in each direction. a)From the connector to the points. b)From the connector to the coil. If its good in both directions then the connector is suspect and you may want to replace it with a 2 prong trailer light type plug.

2) Take the points out and make sure they open and close electrically. Again use the ohmeter and dont worry about values just make sure you see a sharp change. (if they dont then go to 4 and 5)

3) The Clymer fails to tell you that light never really goes out it just goes dim on the MR175. It wont because of the of the pickoffs on the stator windings for the MR175 which doesnt have a battery but uses the pickoff for the lights. Sooooooooo just look for a change in brightness when you hook it up, rotate the rotor clocwise and watch the index line on the rotor, when the T aligns with the index on the cover it should dim. If it doesnt open your points with the two marks aligned and try again. Trust me the manual is spot on except the light does not go out 100%. .

4) Look at the nut on the points where the stator wire connects. You may have to reverse it. That is if the nut is facing out it could be grounding to the stator, Take the whole screw, insulators, (dont loose them) and put the nut on the inside of the point assembly.

5) If you happen to take the electrical connection screw off the points you may of lost the insualtor and that screw is now intermittely grounded to the points chassis.