no spark!!

[stigg]

ok this is really buggin me.. 74 dt100. 2000 miles. no battery but i just jumped them together.. it was gettin a good flash(not solid when i kicked it over) from my light probe up to the coil.. but no spark at all from it.. so i bought a new coil and new plug and new plug boot.. still got good power to the coil but nothing from it... bad ground??? ive checked everything the ignition switch and kill switch both work fine.. all the wires are hooked up right.. i removed the diode that keeps it from "reverse starting" cuz i was tolde they go bad easily and nothing still

 

[interceptor]

Ok, so the bike you have looks to be an on/off road bike. 2 stroke? Probably. You have a good coil, spark plug wire, good magneto, and a good rectifier? Wiring is good from kill switch, and you have power at coil, but not at the boot? Did you check continuity from one side of the spark plug wire to the boot? New spark plug? Might be wrong spark plug. Did you try putting spark plug in and trying to start it? Maybe your testing it on a bad ground. Did you try starting spray? (Be sure to get the stuff for 2 strokes though) Maybe your getting spark, but no fuel. Lastly, I can't remember on your post if you said you jumped the wires for the battery to try to start, or took the battery out. Seems like you would have to rewire some to get rid of charging circuit. Did you clean your magneto?
These are things i would look for. Good luck.

 

[stigg]

ok cool thanks man! its super late like 2am and the bike is now 100% apart.. im gunna make my own wire harness tomorrow.. set it up with no battery etc because it doesnt need one.. they are kick start only and alot of ppl run them without anyways.. its an enduro(soon to be street only) 2 stroke oil injected 97cc single.. so i dont have to premix or anything like that.. i did try starting spray as my tank hasnt been hooked up since i got it cuz it had 5 year old gas lol.. i have power at the coil lead(from the points?) but the coil is not producing anything before or after the boot.. which btw is new ngk.. i suspected bad ground and when i just took the harness off there wasnt one spot that was grounded... except the small ring that bolts up with the coil(coil bolts to frame.. i think it is its own ground though?????)..

how would i clean a magneto?(dremel?) the flywheel is really corroded looking but everything behind it looks new.. i dont have a flywheel puller so i cant take it off either

 

[interceptor]

You can clean your magneto with a dremel with a wire wheel attached, or use scotch brite pads. Clean the magnets on the flywheel, and the surface on the stationary piece. Simply unscrew stationary piece, clean surface, and screw back on. To determine distance between magnets on flywheel and other surface, put a business card between them, let the two attract and tighten bolts. If that doesn't work, I would say that your wiring is screwed up somewhere. Maybe to the coil, + to -, or - to +. You should probably have a voltage regulator too, right? Don't want to much juice going to those lights and popping all your bulbs. Here's a link to a good forum that might help.

http://www.yamahaclub.com/forums/topic/13013-dt100-lighting-qiestion/page__st__30

also, just for some good reading:

http://www.morrismagneto.com/magneto.html

Good luck with the wiring harness. Mine took me a month to do. Long time I know, but I was learning as I was going.

 

[crazypj]

Flywheel magneto on that bike doesn't need battery to run (I think it would if it was a DT125E, haven't worked on one since 1984 though)
You need some bronze feeler gauges so you can set points gap between 0.012"~0.016" , 1.87mm BTDC (good luck finding someone who actually knows what that means)
They didn't get electronic ignition until mid 80's.
Outside of flywheel really doesn't matter much, the magnets are on the inside.
You may have burned out second coil by connecting battery to it
BTW,
stigg, your an idiot.
You started with a nice/reasonable bike then screwed it up.

 

[stigg]

i never.. never hooked a battery to this bike since ive had it.. and i dont see why im an idiot? i got this bike cuz the motor had alot of work done and i paid less than $200.. sounds like a good bike to start with to me and thats why i got it in the first place.. i thought this forum was about customizing not getting "nice/reasonable bikes" to leave them sit and look like "nice/reasonable bikes" thanks for your input though.. i have some of the feeler gauges already (btdc means piston is all the way to the lowest point right? sorry im newby) and i ordered a flywheel puller today too.. only $10 online so i figured i might need it in the future anyways.. btw according to my new multimeter(cheap $25 equus from autozone) both coils are good.. and yes the bike has a voltage regulator and a rectifier and both are good..


OH i see why im an rtard thank you so much for clearing that up!!! i need a book for these! im lucky you posted today man! lol what is a good manual for these? any input is appreciated!! thanks

 

[interceptor]

Hey man, your not an idiot. Maybe I am. Does the bike have a camshaft, valves and adjustable points? I was thinking that it was more like a traditional 2 stroke 1 cyl engine where the flywheel simply slips on the crank via a keyway. (Your bike has a magneto, I looked it up, so I don't know why you would have adjustable points.) Anyways, holla back and let me know. BTW, the best way to learn, for me anyways, is to just start doing what your doing. Investigate for answers and then do it yourself. Good job!
BTDC= Before top dead center. When the piston is almost to the top of the stroke.

 

[crazypj]

Hey man, your not an idiot. Maybe I am. Does the bike have a camshaft, valves and adjustable points? I was thinking that it was more like a traditional 2 stroke 1 cyl engine where the flywheel simply slips on the crank via a keyway. (Your bike has a magneto, I looked it up, so I don't know why you would have adjustable points.) Anyways, holla back and let me know. BTW, the best way to learn, for me anyways, is to just start doing what your doing. Investigate for answers and then do it yourself. Good job!
BTDC= Before top dead center. When the piston is almost to the top of the stroke.

They didn't get electronic ignition until mid 80's.

Stigg, what was it you 'jumped them together'?

OK, so Interceptor is the idiot.
Its a two stroke, reed valve, piston ported, flywheel 'magneto'

It has points.

Bad advice is worse than no advice

You can either listen to someone who has worked on them or not.

 

[Rocan]

two newbies in this thread... Listen to PJ on this one. He may come off as a SOAB but he knows his shit, and not listening to him gets you nowhere.

i say if you want to build the bike into a cafe, go for it. PJ is probably saying that its a better dual sport stock then it would ever be with tons of mods to make it into a cafe.

Also, if its a street bike, youll need a battery for the turn signals and/or headlight and tail light.

good luck.

 

[stigg]

hey pj all i did was hooke the + cable to the - cable lol i didnt know if i had to or not cuz like rocan said im a newb to bikes.. only my second one and the first time ive tried electrical. i cant find a clymers for it either im gunna have to feebay it i guess..

oh thanks for the btdc! iyeah it has points.. but i cant tell if the points are sparking.. i turned the rotor until the points opens all the way(the crank lined up with a tab behind the rotor too so i think it was the right way) and still no spark.. i tested both coils with a ohm meter and they are good.. the magneto is in bad shape it is corroded so maybe stuff behind it is in bad shape too.. thanks



btw im gunna run this thing as a enduro.. im now looking for a cb100 to do a cafe style single with

 

[Rocan]

spark wont be made by just leaving the gaps closed... hold the spark plug body to the engine fins, kick it over, and see if there is spark like that. the spark plug must be grounded (the sides of it) for there to be spark.

cb100 is a great cafe bike... but cb350 might be a better choice depending on how big you are... plus cb350's are easier to find and have way more aftermarket.

if there is spark, then your not getting fuel.

 

[sebatron]

cb350 has more performance aftermarket, but the cb100 has more cheap, easily accessible south-east asian manufactured spares, OEM, OEM-copy and aftermarket. it's when you look outside the square on a cb100 that it gets interesting, or you get inventive.

PJ indeed knows what he's talking about, in case he needed another vote of confidence.

interesting bike, love to see where it ends up. despite my tall stature, i dig the hell out of the 3/4 scale motorbikes

 

[stigg]

im only 5'7 150lbs so im pretty small thats why i like the smaller singles lol

yeah i had the spark plug grounded on the fins i think a wire might not be hooked up behind the magneto its hard to really tell.. specially since i really dont know what im lookin at.. ill figure it out tho..



pj i decided to google stator and found an ebay listing for one.. looked at the pic and the part i circled is dangling behind the magneto and not connected to the rubber part.. i got it to spark for a sec im guessing it touched it.. if you can see in my pic im 100% sure thats my problem.. just would like your input if i should buy a new stator or solder that back on? thanks

as you can tell its corroded bad under there.. im wondering if the person who did the engine work "fixed" this part aswell lol

 

[crazypj]

That's the condensor.
The two coils on back plate are :-
left, source coil for ignition,
right, lighting coil.
You have a half wave rectifier somewhere as battery is required for indicators and tail/brake light (headlight runs 'direct' AC)
If wire is off condensor it won't spark
Probably no connection between source coil, points, condensor and ignition coil
I would check price of new points and condensor.
If Yamaha dealer isnt interested, try Suzuki TS100/125, GP 100/125.
Aftermarket is also OK (maybe eBay or in Britain?)
Your going to have to buy or borrow a flywheel puller (less than $10.00 aftermarket) and a 17mm socket. (remember lefty loosy )
(it's possible to remove flywheel without one, but generally destroys it)
The woodruff key should stay in 'slot' in mainshaft but check.
The points gap also adjusts timing so is pretty important.
You can check points cam when you have flywheel off, its about 20 thou higher than rest of boss that fits onto crank.
If you don't have a multi-meter, get one, doesn't need to be expensive, $4.99 Harbor Freight special does everything you need
Rocan,
Don't know where you got CB100 from?
DT100 is a two-stroke, it's pretty easy to modify for more performanceif you know what your doing. (which I do ;D)
Even stock as a trail bike (wide bars, upright riding position) it will easily do 65mph
Modified plus clip-on+rearsets, somewhere around 90mph+

 

[stigg]

thanks! well i do have a multimeter its $25 equus i got at autozone.. i bought a new flywheel puller and got it all apart cleaned all the corosion soldered it all back together and no power at all now.. ugh.. oh the rectifier is up under the tank so i know i got that.. i put the multimeter to the test and i think i grounded it out somehow but i cannot find where.. im just gunna heed your advise and get new points and condensor.. man there was soooo much rust/corrosion i cant believe it..


btw i would love to do 90mph + lol ive been reading the 2 stroke tuners handbook some great info in there!



pulled it back out and tested the condenser and its not doing anything so i guess i need a new one(or 5).. the points look brand new tho so ill leave them in and just get a few extras just in case something happens on the road..

 

[crazypj]

http://en.wikipedia.org/wiki/Capacitor

I've never used this test but it should work(?)
http://www.classictruckshop.com/clubs/earlyburbs/projects/trouble/ignition.htm 3rd one down shows condensor testing with multimeter

The correct way to test is with capacitance meter measuring in mfd.
I found this online
The proper way to test condensers/ capacitors is with a capacitance meter. You can type in the words capacitance meter in either YAHOO, or GOOGLE, and several companies that make and sell them should show up.
A capacitance meter measures mfd micro ferads. The mfd's are the ability to store energy until it is released. Simply having a condensor that is'nt shorted out is not enough.... To high of a capacitance will cause one side of your points to pit, and the other side to peak up whereas the points don't get a good flat contact. to low of a capacitance causes the same effect in the opposite serfaces. You can buy condensors of specific mfd capacitance for the application needed. For instance a Maytag 92 uses a condenser of about .20mfd's the solid state capacitors work also, but there has been some discussion as to them holding up under vibration, and heat. I know they work well in some applications. If you can't afford a capacitance meter, most automotive electric shops will have one, and some parts stores. probably not the chain auto stores. Now I'll probably have 87 experts tell me I am wrong, but that's my story and I'm sticking to it. I does matter what the mfd capacitance for what application is or is required. other wise you will just burn up the points ....pitting, peaking etc.