1975 Yamaha Dt400 troubles/no spark

[ARCHIVED THREAD] - 1975 Yamaha Dt400 troubles/no spark

Posted: 8/13/2006 9:47:07 PM EDT

I just traded some toyota parts for a dt400. I cleaned everything out. My buddy who traded me the bike said it was the coil. Said he couldn't get any spark. Well, when I started working on it. I checked and had spark. So I didn't think it was the coil. Well, bike wouldn't start. So, I checked the ignition, kill switch, stuff like that. Nothing. Took the carb apart, the float was sticking, and a piece was put in wrong. So fixed it up. Tried to kick it over. Nothing. Changed plug. Nothing. Gas in the plug hole. Nothing. No spark. So, figured the coil was intermittent. Bought a new one. Still nothing. Battery is fine. The only thing I messed with between checking spark the first time and the second was the headlight. Didn't need it, so I disconnected it. Do I need it connected for the bike to get spark? I don't think I do. So I'm thinking magneto, short somewhere, just everything I can try electrical. Not very good with electrical. In fact I hate it.

CAN SOMEONE HELP ME START MY DAMN BIKE???

Posted: 8/13/2006 10:26:19 PM EDT

[#1]

Those are badass bikes. I don't have anything for you, but wanted to make sure you knew.

That is all.

Posted: 8/13/2006 11:57:59 PM EDT

[#2]

Yeah I know. I watched my buddy try and ride it after he punched it 40 over. Couldn't keep it on the ground. But it was his first bike. I just wish I could get the old girl started.

Posted: 8/14/2006 12:33:42 PM EDT

[#3]

You had spark initially and changed the coil and now you don't have spark? Put the wire back you disconnected and see of you have a spark. Several things can cause a 2 stroke not to start. When was the last time the bike was running?

Posted: 8/14/2006 2:31:46 PM EDT

[#4]

On my old CB175 I was having plenty of spark problems as well. Pull the spark plug caps from the wires running to the coil and make sure that the two parts are mating enough to get plenty of current to the plugs. I know that was a major problem on mine, along with adjusting the came chain (which it seems you would not have on this bike anyways).

Posted: 8/14/2006 2:32:31 PM EDT

[#5]

What kind of shape is it in???? Take it on the road,nothing like riding a smoky ring-ding for laughs & giggles!

Posted: 8/14/2006 4:07:30 PM EDT

[#6]

You may have to get into the electronics on the side of the case. its probably out of time. Do you have a dwell meter? Id get a manual and really check into the magneto? if it has one as a charging system.

Posted: 8/14/2006 4:20:41 PM EDT

[#7]

Does it have points or is it CDI? if points you should be able to see them throough the slots in the flywheel. if it does have points they often look clean but will have some corrosion on them and will not make contact so replace them or hit them with a points file and see if that helps. if CDI (electronic you may be screwed, not sure if there are any black boxes still out there for them.)

Posted: 8/14/2006 10:04:45 PM EDT

[#8]

no, I had spark when I got it, but after I cleaned the carb it wouldn't start still so I checked for spark again and didn't have any. So I bought a new coil and I still don't have spark.

The bike ran 6 months ago. The gas was green when I got it so I flushed the tank and cleaned it up. Then cleaned the motor out. But that was before I checked for spark the first time.

I hate wiring and electronic stuff. It always gets me confused. I'd rather strip the motor down to all it's parts than mess with the wiring. I had to fix the kill switch because the wire was cut and shorting out on the switch cover and I was worried I would screw something up then. I am trying to think of something I might have screwed up along the road that would effect the spark. Weird thing is the taillight and headlight wouldn't work either. Ever.

I don't know. I am hoping it's an easy fix and just something I am overlooking. I'll have to take a peek at the points and see if they are all good.

Posted: 8/15/2006 10:29:29 AM EDT

[#9]

Replace the points and condensor and the spark plug cap and wire. Make sure to gap the points and set the timing. Best to time it with a dwell meter but it can be done easily with a points checker/ohm meter.
You can actually set the timing with a piece of cellophane off a cigarette pack and gap the points with a matchbook if you know how.

Really and truly, the timing is best set with a dial indicator but let's not venture there, that's more racing teritory. The marks on the case and the flywheel should do.

Posted: 8/15/2006 12:44:46 PM EDT

[#10]

your main problem is this bike is over thirty years old

Posted: 8/15/2006 5:29:33 PM EDT

[#11]

Quoted:
your main problem is this bike is over thirty years old

Yeah,but think of the coolness factor,he'd be the only one with a DT ring-ding!

Posted: 8/16/2006 1:41:12 PM EDT

[#12]

The bike is actually is really good shape. I would love to drive it around town. Save on gas.

Posted: 8/17/2006 2:42:19 AM EDT

[#13]

I think you are going to be surprised at how thirsty that bike will be...

Posted: 8/17/2006 8:01:06 AM EDT

[#14]

Quoted:
I think you are going to be surprised at how thirsty that bike will be...

I owned an RT1 that was a 360cc it was made a few years before yours. The best fuel mileage i got was 35mpg.

Posted: 8/17/2006 9:57:40 AM EDT

[#15]

35 to the gallon plus two stroke oil = might as well take the car if fuel costs are the reason for riding. Be a hella fun commuter though...

Posted: 8/17/2006 10:29:33 AM EDT

[#16]

My first bike was a DT100. Got it and a bonafide street license when I was 15yo. Rode the wheels of that thing the first summer I had it. Sorry no help for your bike other than checking the resistance on your spark plug wire.

(off to search for a DT on ebay)

Posted: 8/17/2006 11:57:01 AM EDT

[#17]

Quoted:
The bike is actually is really good shape. I would love to drive it around town. Save on gas.

You'll be the only one on the road with one. Most dual purpose bikes end up with the lights taken off(or ripped off) and run like an MXer. They are NOT as durable as an Elsinore/RM/YZ....... so they almost always either end up in the barn,or junked outside said barn.

Posted: 8/17/2006 1:54:29 PM EDT

[#18]

Well, if it gets 25 mpg, it'll be better than my nissan pickup and my toyota truck. And you are right, I will be the only one on the road in my city with one. I like the coolness factor. Plus it bored 60 over, so it'll haul some ass. I think I got the bugs worked out now. It runs, just needs some carb adjustment.

Posted: 8/17/2006 2:46:32 PM EDT

[#19]

well,
WHAT WAS THE PROBLEM?????

(I picked up a PAIR of 1974 DT250s a while back.One whole (mostly) and the other for parts.Gave $100 for the pair.figured I'd part them out if nothing else.
Had spark,so pulled and cleaned tank,replaced hoses,fuel,cleaned carb,back together,and no spark!!!
Did not TOUCHanything else!

Haven't had the time to look at it since.

Posted: 8/18/2006 2:01:17 PM EDT

[#20]

Damn, you have the same problem I did. I just checked all my wires and everything. Then one day it had spark.

Posted: 8/18/2006 2:09:28 PM EDT

[#21]

You have spark now. Did it start?

Posted: 8/18/2006 4:30:25 PM EDT

[#22]

yeah, runs like a raped ape. Had to do some adjusting on the carb, but it runs like a champ. Don't know what was causing it to not spark, but it's fixed. Weird old bikes. Gotta love em though. Found a 77 camaro that I might be trading the bike towards though, so I'll have to enjoy it fast.

Posted: 8/19/2006 1:49:58 AM EDT

[#23]

Quoted:
yeah, runs like a raped ape. Had to do some adjusting on the carb, but it runs like a champ. Don't know what was causing it to not spark, but it's fixed. Weird old bikes. Gotta love em though. Found a 77 camaro that I might be trading the bike towards though, so I'll have to enjoy it fast.

No,keep the bike,and buy the car,that way you'll have both!

Posted: 8/20/2006 9:41:46 AM EDT

[#24]

I wouldn't get rid of it. It's too bad I wasn't closer I'd take that bike off your hands.

Posted: 8/20/2006 11:49:10 PM EDT

[#25]

It's official. The bike is fast. Like really fast. And a tank of gas lasted me all Saturday night. Which is cool, because that only like 1.5 gallons. Normally in my truck I use almost 4 or 5. And I didn't exactly keep the bike under the speed limit either. But I decided the keep the bike. I think it will be worth it. The camaro sold anyway.

Thanks all for your help. I'm getting 2 more dt400's for parts bikes. Now I can complete 1 and make it really nice. But I am more than pleased with what I got for $100 in parts I don't need and that I got for free.

Posted: 8/21/2006 6:08:07 AM EDT

[#26]

Quoted:
It's official. The bike is fast. Like really fast. And a tank of gas lasted me all Saturday night. Which is cool, because that only like 1.5 gallons. Normally in my truck I use almost 4 or 5. And I didn't exactly keep the bike under the speed limit either. But I decided the keep the bike. I think it will be worth it. The camaro sold anyway.

Thanks all for your help. I'm getting 2 more dt400's for parts bikes. Now I can complete 1 and make it really nice. But I am more than pleased with what I got for $100 in parts I don't need and that I got for free.

Congrats. So what was the exact problem?

Posted: 8/21/2006 8:58:53 AM EDT

[#27]

I think it was the wire from the kill switch. It was frayed a little bit and touching the metal casing on the grip. So I cut it and stripped it, then re-soldered it back to the switch. At least thats what I am going to attribute the no spark to.

[ARCHIVED THREAD] - 1975 Yamaha Dt400 troubles/no spark

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