help please

[Steven Klimaszewski]

i have a 1980 yamaha dt 175 i change the rings and pistons it has very good compression and spark but wont start i tryd starting fluid the carb is new and is getting gas to the to the cylinder i tought maybe it could be getting weak spark what would it most like be ign coil or stator also the bike has been complete stripd no kill switch and the and sthe on off switch up put the key n is gone to i think its calld the MAIN SWCH STRGLCK could that cause weak spark and can you rebuild a coil ur self not sure what to do i got this bike from a friend who past away i he never had it running would love to get it back running any help would be much appricated.

[deetee65]

did it run before you changed the piston rings ?

if it did and not now , you might have an air leak in the base gasket , carb to cylinder area .

if the engine didnt run before you may still have an airleak from the crank seals

will the engine run on a prime through the spark plug hole ?

[Steven Klimaszewski]

ya it ran before it gets gas from carb has real good compresion new gaskets does not start with any type of prime it has spark but looks like a small spark my lawnmower show more spark than my bike i test the plug in the lawn more to see how it sparks same color but smaller on the dirt bike its just a push mower i tryd running with the bike and releasing the clutch nothing not even a sound of wanting to fire only thing i can think of is electrical or spark i get shock from the spark plug but not enough to make me take my finger off i tested the wire going to the coils from the black box that gives me a little shock bout as much as the plug does dont know where to start stator or coil i can send you pics if you wanna see the bike thanks for any info you can give thanks

[Airhead]

it does seem the faint spark mey be an problem, try this

DT175MX Ignition checks

There were two versions of ignition systems on DT175MX bikes. The mk1 version from the earlier bike had a 7 wire CDI the early bikes had a round section swing arm.

The mk2 version had a 6 wire CDI, the red wire is absent on these. These bikes have a square section swing arm.

The HT cap (AKA spark plug cap)

unscrew it off the HT lead, it is supposed to be a resistor cap so should be around 5K Ohms

The ignition coil primary...Orange wire to battery neg should be 1 Ohm +- 10%

The ignition coil secondary...HT lead to battery neg should be 5900 Ohms +- 20%

If the readings are much higher, check the ignition coil has a clean ground connection.

Yes and the ignition coil mounting is a wiring harness ground point too, so check its clean and bright there.

Disconnect all the wires from the CDI.

Then using your multimeter on the loom side of the connectors.

Black probe on a clean part of HT coil ground point

Red probe on......

Orange, Meter to 200 Ohms, expect 1 Ohm (HT coil primary)

Brown, Meter to 2k Ohms, expect 420 Ohms for mk1 and 300 Ohms for mk2 (Magneto charge coil)

White/Red, Meter to 200 Ohms, expect 12.4 Ohms for mk1 and 10 Ohms for mk2 (Magneto pulser coil)

Red, Meter to 200 Ohms, expect 13.6 Ohms for mk1 only. (Source coil 2 or high speed coil)

Black female connector, Meter to 200 Ohms, expect dead short

repeat for black male connector

Any difference in the results for the two black wires may possibly be rectified by cleaning the front engine mounting bolt and a little of the frame behind the bolt head, then tighten to torque spec.

Black/White, Meter to 20K Ohms, with ignition off expect dead short, with key on expect open circuit, with kill operated expect dead short (Engine kill operation)

If all these tests are good you would be well advised to try another CDI.

If they are not good...reading higher...disconnect and clean any plugs/sockets you find along the way, if the magneto coils are reading lower, new ones needed if more than 10%...or so the book says

Finally, if you are working with a box full of mixed parts!

Mk1 1 flywheel is Mitsubishi F3T250, it has two slots in the face of the flywheel

Mk2 flywheel is Mitsubishi F3T251, it has four slots in the face of the flywheel

[Steven Klimaszewski]

mine is a 1980 dt175g it has been stipd down befor i got it it no battery lights ect. even the main switch that the key goes in is gone no kill switch ... there is a orange wire that come out of the black box to the coil i think its a cdi box asy from the diagram i looked at i dont have a omhs meter so i un cllip the orange wire n get shock through it but not much the hard i kick it over the more shock it gave my fingers not sure whats up iam lost

[Airhead]

mine is a 1980 dt175g it has been stipd down befor i got it it no battery lights ect. even the main switch that the key goes in is gone no kill switch ... there is a orange wire that come out of the black box to the coil i think its a cdi box asy from the diagram i looked at i dont have a omhs meter so i un cllip the orange wire n get shock through it but not much the hard i kick it over the more shock it gave my fingers not sure whats up iam lost

dt175g is the same as DT175MX mk2 as far as i'm aware so the checks i posted apply!

get yourself a multimeter and do the checks if you are serious about getting this thing fixed and stop trying to measure success by the degree of pain it gives you.!

dont forget to post a proper intro in new members forum...

[Steven Klimaszewski]

also i have to extra wires comeing out off cdi box solid black and a black with white strip i know nothing about the wireing on this cause when i got it it was stripd down no kill switch ans no key/inignition some told me that thead light has to be hooked up and new wire harness for bike to work sounds far out there but if you give me your email i can show you what iam working with never worked on a dirt bike befor so not sure where to start tryin to find a ohms meter to thanks