How to make a DT 125 go fast and handle good

[GMC]

If the sow's ear challenge appeals

I think the appeal is to turn a sow’s ear into a fast sows ear.
Finesse is a word Dave will have to look up in the dictionary too.

I don’t think he can be bothered splitting the cases to change ratios.
The motor is already out and on its way to Jimmy (Dynotune)

He is probably going to pressure me for a pipe for Easter, hope he reads this and makes a note not to run over me at Denman

Seems it’s a 75 DT model and according to Zedder it’s the same as the 74 – frame, cases, crank, wheels, forks, gears etc.
 
Nearly went bonkers the other night studying Zedder to work out ratios.
It only lists the number of teeth on some part numbers and from what I could make out the AT2M and the ATMX have the close ratio boxes in the early models.
The MX 125 seems to have the same ratio’s but has different part No’s.
I assume they are interchangeable as a set and not individually?
The late model RT100 also shares the same gears as the DT

[Nathan S]

  Is it definitely the AT1 style bike, with the full backbone frame (a la early monoshock Husky) and leg-burner pipe?

AT1 vs MX-A gearboxes are surprisingly different. I THINK you could make the MX box fit the earlier bike, but the shift drum has to match the box (different placing of individual gears in the box), and that would give you a road-race shift pattern (1-up, 4-down). And it would need some tricky/annoying machining to get the shift drum to fit the 'wrong' cases.

[NSR]

The 1974.5 DT125A with the brown/burgundy tank is a variation on the 1974.0 DT175/YZ125A/MX125A platform, and is a much better bike.

My first real bike.  Rode it in my first enduro, it took most of the riders 4hrs it took me about 8hrs .  Had a geat day.  Go fast handle good, Nah,  I loved it though.      

[GMC]

Is it definitely the AT1 style bike, with the full backbone frame (a la early monoshock Husky) and leg-burner pipe?

Danged if I know.
I have been unreliably informed that it’s a 75 DT

Was it 78 that the DT 125 went to monoshock or was that only the 175?

[Tex]

Was it 78 that the DT 125 went to monoshock or was that only the 175?

I think it was, though there might've been some monoshock ones available by late '77.






Mine's the one without the pretty girl (story of my life really)

Tex

[Nathan S]

The monoshock 125 I had, had an early-mid 1977 compliance date. I always assumed it was a 1977 model?

And pointless trivia time: The late twin shock frames are different to the early twin shocks - note the bend in the member that runs from the swing arm pivot up to the top shock mount in Tex's photo. Early models are straight.
They also have a sheet metal gusset along the top of the swingarm, and the seat latch is moved foward or behind the shock mount (can't recall which is which, but it oppostie to the early twin shock frames).

[mboddy]

I was assembling motorcycles for Doug Bryant Motorcycles outside school hours in 1977.
From memory we got our first mono shock DTs mid year.
Two crates of 175s and a crate of 125s - each crate had two bikes.
After assembling the first two 175s I went into the office and bought one of them.

[Mike52]

He could do what all the Yammy 125 enduro guys did.
Put a DT compliance plate on a YZ.
$24.95

[John Orchard]

The AT1E was the electric start model wasn't it?

[vandy010]

Geoff,
is it like this?

or this?

now, back to you Nathan

[Nathan S]

Geoff,
is it like this?

Never seen/heard of one of those?!

That's the old AT1-based bike, but with 1975/76 colours?!

Either its copped a respray, or Yamaha was selling two different models in different parts of the world. Considering what they did with the later MX100 and single cam XT250, anything is possible.

My race bike (that's been sitting in the shed for five years now) is the MX125A based bike, that is the model between those two. It had the DT250A shaped fuel tank on it.
452 prefix???

[GMC]

Geoff,
is it like this?

or this?

now, back to you Nathan

Apparently he has one of each (glutton for punishment)
He is doing up the early one (straight frame tube)
He rang me the other night about a pipe for Easter
I think my laughing answered his question

[Nathan S]

If its the MX125A style bike, then one of your YZ125A pipes will work. Might hit of the fins of the cylinder head.

Easter 2014 shouldbe do-able?

[Canam370]

Best way? Buy an SWM, pull out the wheels, bend the forks, ride on the sprocket. It'll still be better than anything you'll do to a DT to try improve it 

[GMC]

Best way? Buy an SWM, pull out the wheels, bend the forks, ride on the sprocket. It'll still be better than anything you'll do to a DT to try improve it 

After having ridden an SWM at Denman I’m inclined to agree with you.
Apparently Dave may have felt the same way because a CanAm has snuck in during the middle of the DT build.

DT motor now bored and ported.
Frame tidied up and powder coated.
Wheels are off being respoked.
Soon to have pipe and airbox

Now a small dilemma.
I couldn’t get the plastic swingarm bushes out of the arm without destroying them so decided to take our chances in the powder coat oven.
They didn’t survive.
Can you buy these off the shelf anywhere or do I need to machine up some brass bushes?