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1974 DT125A Build/Restore

  • torqueflight
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1974 DT125A Build/Restore was created by torqueflight

Hey guys just picked this up the other day. Only 420 miles and bought it on 4/20. Super excited to get it to run. Was looking for something mid sized and vintage to put on the back of my truck on a platform. As a bonus its a 2 stroke. The title was missing, so I guess we shall see how fun thats going to be in California.

The previous owner bought it off a farm and didnt have time for it, so he flipped it. He said the engine was seized to someone riding it without oil. 

The first thing I did was pull the plug and pour in some marvels mystery oil. Then I just slowly kept applying pressure of the kick and it came free. I pulled the expansion tube and the cylinder looked brand new. It still has the cross hatching pattern on the cylinder wall. Also the 2 stroke oil tank was full. So I think the guy might have been wrong about it being seized by running it without oil. I think it was just seized from sitting. 

Definitely gonna need some help with this thing. Been researching as much as possible but theres somethings that arent easy to find. 

It missing the key which sucks. Im hunting ebay to find one that fits before I try and change everything. 

One bad thing though is, I might have to pull the top end off. It seems it was stored with the throttle barrel open, and I think when I kicked it over it sucked dirt into the cylinder. It appears the rubber that goes between the airbox and the carb was missing. Im also having a hard time find which one is the right one.

The front forks might be bent. The tire is point more to one side, not aligned with the bars. Not sure if I should look for the same forks or if there is an upgrade. 

So far I have a seat cover coming. Need to order new throttle cable and brake cables. 

Hey guys just picked this up the other day. Only 420 miles and bought it on 4/20. Super excited to get it to run. Was looking for something mid sized and vintage to put on the back of my truck on a platform. As a bonus its a 2 stroke. The title was missing, so I guess we shall see how fun thats going to be in California.

The previous owner bought it off a farm and didnt have time for it, so he flipped it. He said the engine was seized to someone riding it without oil. 

The first thing I did was pull the plug and pour in some marvels mystery oil. Then I just slowly kept applying pressure of the kick and it came free. I pulled the expansion tube and the cylinder looked brand new. It still has the cross hatching pattern on the cylinder wall. Also the 2 stroke oil tank was full. So I think the guy might have been wrong about it being seized by running it without oil. I think it was just seized from sitting. 

Definitely gonna need some help with this thing. Been researching as much as possible but theres somethings that arent easy to find. 

It missing the key which sucks. Im hunting ebay to find one that fits before I try and change everything. 

One bad thing though is, I might have to pull the top end off. It seems it was stored with the throttle barrel open, and I think when I kicked it over it sucked dirt into the cylinder. It appears the rubber that goes between the airbox and the carb was missing. Im also having a hard time find which one is the right one.

The front forks might be bent. The tire is point more to one side, not aligned with the bars. Not sure if I should look for the same forks or if there is an upgrade. 

So far I have a seat cover coming. Need to order new throttle cable and brake cables. 


 

 

 

 

 


 
24 Apr 2021 23:11 #1

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Replied by torqueflight on topic 1974 DT125A Build/Restore

The stator cover was missing. I have one coming from ebay. Also dont know anything
about points so Im guessing its gonna be a b chasing this thing out. 
 

 

One thing I noticed is, some bikes have 2 plugs. It appears there is a spot for another plug but its plugged. 
There is only 1 output on the coil though. What would be the point of the 2 plugs?
 

Need to find another factor front fender. Might actually try and fiberglass this one for fun until I find one. 
 

 
24 Apr 2021 23:17 #2

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Replied by Mothersbaugh on topic 1974 DT125A Build/Restore

Welcome. Don't do anything without asking here (and waiting for an answer) for help!! Front fenders are plentiful and cheap on ebay; that fender was used on a lot of bikes. I bought one for $20 delivered. Search Vermont title, and there should be plenty of infor on how to title the bike through the state of Vermont, regardless of where you live. Looks like you need foam on the seat as well. Oil pump checks and rebuilds? Go through DEET, a member here. Second plug was a spare. Change out the transmission fluid; change out the oil tank with new Yamalube 2S. CHANGE AT LEAST YOUR FRONT BRAKE SHOES. The old one can delaminate over the years, and they can lock the front wheel on the bike and send you over the bars. There are manuals for many, if not most, bikes in the Tech Library; find that division in the tool bar above. There are ebay-ers who will cut you a key using the four numbers on the face of the switch; don't change the switch! Check with kdirepros.com for cables, even cable sets. He's a membner here and makes them, and he has brake shoes, too.

That should get you started...and keep you out of trouble for a few days, huh?
Again, welcome.
25 Apr 2021 05:50 #3

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Replied by tennbamaman on topic 1974 DT125A Build/Restore

Nice bike and great project for you. Im trying to get my AT1C running right now. Im in the early stages as well.
25 Apr 2021 06:14 #4

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Replied by RT325 on topic 1974 DT125A Build/Restore

Good model 'that' & had one myself years ago. Hope its only locked up from sitting & piston has grown into the bore. If she frees up you'll have it running by lunch time. Hook it to your car 12 volts with jump start heavy leads. Give points a scratch while in place, & make sure they're free to open & close if its been sitting out in the open. Hope gene brushes are free but can kick start if starter won't work. Just need 12 volts. I should read the story properly--tomorrow-- but thought i saw no ignition key. If you get in the headlight & unhook the switch then connect red to brown in the loom it should work There's different browns but one you want is a normal light-ish brown. Darker brown is flashers to left or right--can't remember now
Last edit: 25 Apr 2021 06:39 by RT325.
25 Apr 2021 06:36 #5

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Replied by torqueflight on topic 1974 DT125A Build/Restore

Thanks for all the initial help. 

Gonna be super busy this week but Im gonna keep ordering parts. 

I have a key ordered from ebay. We shall see if it actually works. 

Anyone know what to do about forks? Pretty sure these look bent and from what I could tell I dont think you can adjust the front tire independent of the bars????

Also what tires are still available that would be good for canyons and some off road? The tires on there now are all broken at the sidewalls. I had a look last night and the tires that are on the bike are 3.00x19 front and 3.25x18 rear. Also any suggestions for tubes?

Are the small filters still available for the gas petcock? 

Does anyone know how long the oil tank would last for when full? Just curious. 

Any recommendation on transmission fluid?

And as far as some dirt getting suck into the piston and bore, I should probably pull the top end right? If so will I need new gaskets?

The stator cover was missing when I got it and it appears it was sitting out in the weather without it on. 

Thanks
25 Apr 2021 12:22 #6

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Replied by DaveinSC on topic 1974 DT125A Build/Restore

I’m working on the same bike right now and needed the air filter boot too. I found a new reproduction online at Clauss Studios. It wasn’t too bad, I think 38.00 with free first class shipping and it was the only place I could find one. Like has been said you can get a key made on eBay, I had one made for an AT a while back and it worked perfectly. I have a set of hand grips and a new seat foam and cover plus the edge protecting strip coming this week from KDI  that will just about finish my bike up. 
25 Apr 2021 12:23 #7

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Replied by torqueflight on topic 1974 DT125A Build/Restore

Thanks Ill check them out for the elbow.

Also does anyone know if you can still buy an air filter for the airbox?

Thanks
25 Apr 2021 12:26 #8

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Replied by torqueflight on topic 1974 DT125A Build/Restore

Is this the correct elbow for a 74 DT125?

www.claussstudios.com/store/p598/Yamaha_..._Air_Boot_Joint.html

Thanks
25 Apr 2021 12:29 #9

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Replied by DaveinSC on topic 1974 DT125A Build/Restore

I just bought a Unifilter from eBay for 30.00 free shipping. Has the cage inside so it takes care of that as well 
25 Apr 2021 12:33 #10

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