Vintage Dirt Bike Q & A

Hello, looking for help on a older Yamaha dirt bike i just got.

I tinker with bikes, but never really had a dirt bike - and me & electrical work never got along!

Below is a diagram of what I have to work with. I am trying to figure out the following things…

1.) Do I need a Rectifier?
2.) Do I need a CDI Box?
3.) I have no lights, and never will (yellow wire?)
4.) The yellow & green wire are cut off - where do those go?
5.) It does not have a Kill Switch - I was going to put on on but not sure what wire goes where.
6.) It does not have a battery. I assume it's 12V, but there seems like no place to stick/mount it. Can I get by without a battery?
7.) VIN is #443-125305 - does that make it a 1974 or 1975 DT175 bike?
8.) Is this thing Gas & Oil Mix? If so what mix ratio?

THANKS FOR ALL YOUR HELP IN ADVANCE!

...



Looks like:

1975 DT175B - Balboa Blue - 443-100101 to 443-126950


Here is a Shop Manual for your bike on eBay:

http://www.ebay.com/itm/1974-1975-1976- ... 62&vxp=mtr


Shop Manual is a good start.



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.

your bike does not need a battery to run,unless you are putting lights on it for street use.

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

thanks for input! Does bike have oil mixer thing, or do I mix in tank? sorry, dumb question. No money for $30 manual... just trying to figure out where yellow & green wire need to go and how to hook up kill switch.

they have autolube stock.it would not hurt if it is all still installed to mix up some premix and use that to start then check the oil pump output.it should have a oil pump under a small cover on the primary side,a throttle cable to the pump and properly set,a oil tank with two stroke oil in there.use oil designed for oil injection to put in the oil tank.

if testing oil pump output,disconnect the oil line to the cylinder or cab and plug the oil line input on the carb or cylinder.drain the straight fuel from the tank and carb and put in some premix at 32:1 ratio then start the engine and it should drip slowly out of the oil output line at a idle speed.

if the oil injection is removed you can run 32:1 premix in it.

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

any other questions,don't be afraid to ask.....

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

Thanks, wil check that out later today. I'll post pics too maybe that will help me. The only question I have really is the first question I posted - about wiring - but with some new developments.

I can't seem to get a spark. But the green wire that comes out of the magneto thing sparks when I hold wire on head & kick it over.

Q: Do I need they yellow wire hooked up at all for bike to run? It's only for lights right?


Q: Where does the green wire go?

Q: What wire can I splice in a kill switch? Regular on/off toggle OK or does it need to be "feed through" switch? (not sure what hat means someone told me that)

One person told me that the ONLY wire I need on bike is the black out of the stator, and to put a kill switch between the stator and the ignition coil. (i assume in-line on this one black wire?)

What about the white wire that goes to coil? (see drawing above)...

THANK YOU!!!1

Thanks, wil check that out later today. I'll post pics too maybe that will help me. The only question I have really is the first question I posted - about wiring - but with some new developments.

I can't seem to get a spark. But the green wire that comes out of the magneto thing sparks when I hold wire on head & kick it over.

Q: Do I need they yellow wire hooked up at all for bike to run? It's only for lights right?


Q: Where does the green wire go?

Q: What wire can I splice in a kill switch? Regular on/off toggle OK or does it need to be "feed through" switch? (not sure what hat means someone told me that)

One person told me that the ONLY wire I need on bike is the black out of the stator, and to put a kill switch between the stator and the ignition coil. (i assume in-line on this one black wire?)

What about the white wire that goes to coil? (see drawing above)...

THANK YOU!!!1
not 100 percent sure on the 175 but the other Yamaha models use the black/white stripe wire for the ignition.there also should be a diode there to keep the engine from starting up rotating backwards.that diode needs to be there.it hooks up the ignition coil coming from the magneto and you can wire a kill switch to it.run 1 wire from the kill switch to the black/white stripe wire and if it has 2 wires the other wire goes to ground.you can use the factory kill switch which is on the throttle on a Factory throttle.

here is a example. the 1 wire witch goes into the black/white stripe circuit.


all the other wires are for the lighting and battery charge. do you have pictures of the wiring,I would like to see them to make sure.

your bike if it is original there has breaker points and condenser.the CDI on the 175 came out in 1978 to 1981.all earlier models were equiped with breaker points.

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

Thanks again for info. I took a few pics last night - perhaps these will help explain what I have here. There are only 4 wires coming out of the magneto. Solid Black, Solid White, Solid Green, Solid Yellow.

There is NO "Diode" between black wire coming out of magneto and coil. Not on white wire either.

The second black wire coming off the coil (and soldered to wire coming from magneto to coil just goes t a ground on the frame.

MAGNETO WIRES


COIL WIRES


SWITCHES


HELP IDENTIFY


THE BIKE

the little brass stub on the carb is the choke or whats left of it.

on that one picture,the large nut with a screw in the center is the neutral light switch,the other one appears to be a shift drum detent.this originally had a knob on the end.

the wires are different than I thought.does the bike have spark with that white wire connected.I am not too familiar with the earlier 175.looks like the wiring has been hacked on it for sure.with old bikes this is very common.

that handlebar switch is not too expensive to replace.they are all over on Ebay.I got a NOS one for around 22.00.this one is the one I got.
http://www.ebay.com/itm/330964494270

as for the diode.I have heard that when that is bypassed or removed the possibility of the engine actually running backwards does exist.this one I am just passing along from a discussion on another message board about the diode and why it is there.you can try it like that but if the engine kicks back a little and runs in reverse,don't be surprised.

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

Thanks again!

The bike has no spark at all right now.

Does the Diod has a specific name? Yeah, backwards on 2 wheel may no t be a good idea.. a good laugh.. but not a good idea..

regard, T.

I will get with a guy that knows the Yamaha DT175 very well,He in fact was a huge help in the 1978 DT175 I am putting together.

I did some digging and even went to the Yamaha parts site and found no diode mentioned on the 1975 model DT175,perhaps I got this mixed up and it was on the earlier model than the 1974-76 DT175.

there is a spark advance mentioned and it is in the flywheel,similar to what was used on the 1970-71 RT1 360.

the Yamaha parts list site is found at this link.it may be useful to you in the future.
https://www.yamahapartsandaccessories.c ... ELECTRICAL

on the top where it it says electrical there is a pull down tab and you can also look up other parts,it helps knowing part numbers when looking for parts.

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

Hello all . . . a nube to this site, but certainly not to vintage bikes in general!

Dave contacted me, and ask if I'd comment on this thread

Your bike doesn’t need the yellow, green, or white wires …. Only the black
The black wire(s) needs to be disconnected from the bolt that is currently attaching the coil to the frame . . . and also, disconnect the second black wire that's going to ground
Then . . . Remove the white wire that is currently attached to the coil, and replace it with the black wire that you just removed from the coil bolt & ground.

The second black wire is where a kill switch can be connected … if no kill switch is desired, then the second black wire needs to be taped up so that it doesn’t touch anything and end up grounding out the spark.

Sweet,Thanks for coming in Yamadave! Kingplinker,this man is really on it!! if you have DT175 questions YamaDave is the Man!!

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

GREAT! Thank you guys so much! I will try this later today and keep you posted! THANKS!

One more question: Do I need to loop the kill switch back to coil or ground, or ? Right now I have a FLIP switch, does it need to be a single push button type?

SEE: