OzVMX Forum
Marque Remarks => Yamaha => Topic started by: GMC on March 17, 2012, 05:25:15 pm
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A mate is about to start an incredible, possibly unrealistic adventure.
He wants to hot up his DT 125 to make it go fast and handle good, for $43.65 as the letters to the editor would usually say.
It got me thinking, Yamaha had the DT2MX which was I believe Yamaha’s first production 250 MXer.
So did Yamaha have a 125 version ?
It seems they had the RT1MX & RT2MX which were the 360 versions
Can anyone offer up any hot up tips for a DT 125?
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All shit aside Geoff fit one of your YZ 125A pipes and a bigger carb , lighten the magneto and Roberts your mums sisters brother ;)
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Ask Nathan were to send the box of bits............................. ;)
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Twin shock or mono?
The twin shock DT125 is basically an MX125A with a wide ratio gearbox and more crap hanging off it. It's not hard to make one into a respectable Pre-75 125 racer, especially if you use YZ or MX parts.
That said, the single best mod is a set of 250 forks and triples.
With an Uncle Lozza barrel, stock DT pipe, 32mm carby and YZ-E ignition, my DT is way faster than my stock YZ125A...
Monoshock DT125 is closely related to the IT125 and 1980-ish YZ100.
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Here ya go Geoff, A site with all he needs to know. Translate and go for it. A bit more than $43.65.
http://dtmx-passion.forumactif.com/f5-preparation (http://dtmx-passion.forumactif.com/f5-preparation)
(http://i19.servimg.com/u/f19/11/50/18/95/photo_10.jpg)
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Thats cool 8) 8) 8) 8)
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hey Bill put a couple of sinkers and some trace off it and DJ could ride it
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Let me guess....Dave H, right? I can't think of anyone else who'd derive joy from such a task. :D You ought to know better than to get involved in these schemes! Now back to the shed and finish my job.
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I'll bet it's Hammond too. Of course.
This guy loves little Yammies!
(1972 AT2-MX matches DT2-MX era. But it was just an AT1 with a GYT kit; while the 250 and 360 were new bikes. Sexy beasts!)
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AT1/1974.0 DT125A (444 prefix?) is an interesting choice...
Help us out here, Mr GMC!
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If it's pre-mono shock going back to the AT1 then there are heaps of bits out there.
AT1 through to AT3 and DT125/175's ran a wide ratio box. The AT2MX (and the MX125 A & B) ran the same full close ratio box and can be had from http://www.nwvintagecycleparts.com/
1 265-17121-01-00 Gear, 4th Pinion, (16 Tooth)(Now #315-17121-0 $10.00
2 265-17141-00-00 Gear, 4th Pinion, (22 Tooth), (AT1MX,LT2M,LTM $10.00
3 265-17151-00-00 Gear, 5th Pinion (23 Tooth), (AT1MX,LT2M,LTMX $10.00
4 265-17211-00-00 Gear, 1st Wheel, (34 Tooth), (AT1MX,LT2M,LTMX $25.35
5 265-17241-00-00 Gear, 4th Wheel, (24 Tooth), (AT1MX,LT2M,LTMX $10.00
6 265-17251-00-00 Gear, 5th Wheel, (22 Tooth), (AT1MX,LT2M,LTMX $10.00
7 265-17411-01-00 Axle, Main, (12 Tooth Drive Gear), (AT1MX,AT1 $15.00
Third gear is common through the lot.
Ignition is simple, as Nathan said, run a YZ 125 X,D,E plate and rotor. Will need some work to mount on the backing plate but the rest is simple. While your at it, take out the 5 old thick plates and replace with YZ125 C,X 6 metal and fibre plates. Works a treat.
Carb and porting are open but 32mm carb is the ticket. A better reed block with a bigger opening is the go to but can't remember which bike it's from. Bring the head clearance down to. It really makes then crack. Pipe as well.
Get a fork brace and the 250/360 forks. (and find a 21" front wheel with the small hub to save weight).
13" rear shocks to find the front end again. (Not the 12") If your super keen add an 1" or 1.5" to the swing arm.
All this stuff is done to my AT1 which I race at Heaven.
Finally, and this is the most important part, don't start this project until the rider has lost weight and is no heavier than 65kg's.
I know from experience that 100kg's is a big handicap.
They are great fun. They are cheap and there are bucket loads of bits every where.
If it's and early mono shock, YZ125D or E gear set goes straight in (same cases), bigger carb, porting, head, YZ ignition goes straight in. Finding the bits will be a little harder as gear boxes are almost rocking horse stuff! Ignitions are too......
This model hot up is possibly the quickest and easiest.
Either way, an hour at a wrecker or two hours at Nathans and you'll have more than enough stuff to start a fun new life throwing around a little old DT!
Peter B
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Watching Mr. Hammond wringing the neck of that little YZ up the hill on the Harrow mx track was a blast. ;D ;D ;D
If this is another weirdo small bore project, I'd be interested to see what comes of it!
Not many of us old fat bastards can still do a 100 or 125 justice these days........... :-\
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Here ya go Geoff
That's a nice lookin' DT!
I've got a '77 twin shock DT125 and I found that the best way for me to get it to "go fast and handle good" was to get someone else to ride it! ;)
I'll be interested to see what comes out of this project too.
Tex
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AT1/1974.0 DT125A (444 prefix?) is an interesting choice...
Help us out here, Mr GMC!
The 74 DT appears to have the 444 prefix
What makes it interesting?
AT1B - 1970 - AT1 Enduro
AT1C - 1971 - AT1 Enduro
AT1E - 1969 - AT1 Enduro
AT1M - 1969 - AT1M Enduro
AT1MB - 1970 - AT1 Enduro
AT1MX - 1971 - AT1MX Enduro
AT2 - 1972 - AT2 Enduro
AT2M - 1972 - AT2M Enduro close ratio
AT3 - 1973 - AT3 Enduro
ATMX - 1973 - ATMX Enduro close ratio
DT125A - 1974
DT125B - 1975
DT125C - 1976
DT125E - 1978
DT125F - 1979
DT125G - 1980
DT125H - 1981
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Because they're basically an AT1 - a 'quirky' Pre-70 VMX bike, but fundamentally pretty ordinary, particularly among Pre-75 (and newer) bikes.
As the old saying goes "if I wanted to go there, I wouldn't start from here"...
To put it in context, ask whether he/you would want to hot up and AG100, 'cause they're the same basic bike.
If the sow's ear challenge appeals (sorry for repeating a lot of what Peter B has already posted - I forgot he'd posted that up):
Close Ratio gearbox is very useful for MX, probably a significant liability for Vinduro.
Motor shares bore, stroke, crank and basic port lay-out with the YZ/MX so there's lots of potential there.
Too much power will see the gearbox input shaft spin in second gear.
34mm Yamaha forks and triples, and matching 21" front wheel should be considered essential for staying alive above 40kph. If you stick with the stock drinking straw forks, a YZ100 or IT125 front wheel goes straight in and has an alloy rim.
Swing arm is too short, and the rubber bushes make it feel flexy.
Frame is flexy. They should benefit from the old DT1 frame mods, too.
Internal gearing is very short - something like 17/44 sprockets on my old one was still too short for MX. The idea of riding across those paddocks at Harrow on it, causes me to shudder...
The reed block and intake boot are tiny - don't think you'd get more than a 30mm carby in there.
Airbox is also restrictive. AT1M airbox is an improvement, but I reckon it will still limit power.
Bassani pipe seems better than GYT.
CDI ignition from an AG100 goes straight on. I assume the AG's advance curve is rubbish, but you'd be able to swap CDI boxes until you found one that suited.
Footpeg mounts can bend under hard use (my paddock bike bent them all the time, the racer never did!?).
Cush drive rear hub can be swapped with a modified monoshock DT125/175 hub. This makes it pretty much a YZ125A hub, and is legal for Pre-75.
Oh, and because I think I managed to not answer the original question properly:
The short lived 1974.0 model DT125A with the green tank (and maybe other colours) is a mildly rehashed AT2. The few I've seen have all been electric start models.
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.
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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
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??? 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.
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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 :D. Had a geat day. Go fast handle good, Nah, I loved it though.
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??? 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?
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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.
(http://www2.yamaha-motor.fr/actu/IMG/jpg/ym50_doc_k-14-dt125mx.jpg)
(http://www2.yamaha-motor.fr/actu/IMG/jpg/ym50_doc-14-dt125.jpg)
Mine's the one without the pretty girl (story of my life really)
Tex
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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).
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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.
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He could do what all the Yammy 125 enduro guys did.
Put a DT compliance plate on a YZ.
$24.95
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The AT1E was the electric start model wasn't it?
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Geoff,
is it like this?
(http://p1.bikepics.com/2008/05/05/bikepics-1278731-full.jpg)
or this?
(http://p1.bikepics.com/2008/04/19/bikepics-1259115-full.jpg)
now, back to you Nathan ;D
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Geoff,
is it like this?
(http://p1.bikepics.com/2008/05/05/bikepics-1278731-full.jpg)
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???
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Geoff,
is it like this?
(http://p1.bikepics.com/2008/05/05/bikepics-1278731-full.jpg)
or this?
(http://p1.bikepics.com/2008/04/19/bikepics-1259115-full.jpg)
now, back to you Nathan ;D
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 ;D
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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?
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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 :P
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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 :P
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?
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Don't waste your time! It's only Dave stick the bolt back in and tell him it's got two wheel steering if he questions it. Besides he is to busy at the moment trying to find a make up artist to pretty up the Can-am
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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 :P
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.
Yep, quite a nice one at that 8). It was a favour to Drakey really 'coz he didnt want Dave riding his bike again :D
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Yep, quite a nice one at that 8). It was a favour to Drakey really 'coz he didnt want Dave riding his bike again :D
Well judging by what Drakie did to his own bike, not to mention himself I think Drakie is the one that shouldn’t be allowed back on Drakies bikes.
Drakie must have taken quite a bump on the head too as I swear he was about to submit to Dave’s desires, but what happens on the Vinduro trip stays on the Vinduro trip.
So, anyone know where to find DT swingarm bearings?
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Geoff I got mt DT175 ones out of england. To be honest I'd make some bronze ones my are on there way out and they haven't done much work. Curly
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So, anyone know where to find DT swingarm bearings?
Single backbone frame with plastic bushes? I thought they all had rubber.
Brass or nylon would be a worthwhile upgrade.
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I scored this barn find recently. As far as I'm aware it's 1974 DT 125 A. Engine number prefix is 444
Not bad for 200 bucks hey?
(http://i279.photobucket.com/albums/kk145/kipo_bucket/Picture002-14.jpg)
(http://i279.photobucket.com/albums/kk145/kipo_bucket/Picture003-14.jpg)
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Shoulda been 666 ;) Not a bad score at all, and cheap.
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You country boys have all the fun! :D
I suppose you'd go through a few houses in a day's work and it would be worth asking if there's any old bikes kicking around, eh? ;)
Good work!
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Good find, Dave would have snapped that up in a flash, secretly keeping it out of view of his missus, then claiming he needed it to round up the sheep (which he doesn’t have) and then it could have gone into rotation roster with his other DT’s for the Vinduro’s.
I only get to see small pieces of his go-fast DT on different occasions but his build seems to be coming together nicely.
(http://i15.photobucket.com/albums/a393/gmcloa/Misc%20bike%20stuff/DavesDT-3.jpg)
(http://i15.photobucket.com/albums/a393/gmcloa/Misc%20bike%20stuff/DavesDT-1.jpg)
Works replica forks, special light weight forks to help increase acceleration.
Steel rims to help keep the front end on the ground.
(http://i15.photobucket.com/albums/a393/gmcloa/Misc%20bike%20stuff/DavesDT-2.jpg)
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You country boys have all the fun! :D
I suppose you'd go through a few houses in a day's work and it would be worth asking if there's any old bikes kicking around, eh? ;)
Good work!
Yep, always keen to check out the shed!
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(http://i943.photobucket.com/albums/ad275/albrid3/Seeley012.jpg)
found this the other day.
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Did he waste the stock fork legs on the lathe ? he must like his scotchbrite wheel :)
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Its just the photo (Light) Freaky, very original and not tampered with. A good clean YZA
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Its just the photo (Light) Freaky, very original and not tampered with. A good clean YZA
Dave I think Freakys talking about the DT ;D But good score on the YZ 8) very original :) where do you keep finding them ? is this one a keeper ;)
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l think the fellow with the dt 125 is doing a nice job on that bike.
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I think "that fellow" is doing his best 80's glam pose in the picture behind the DT!
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Hi Bill, my son want`s the YZ to race, its being rebuilt, I have just had the barrel re-nickled, new Yz 30mm front fork tubes on their way, new standard piston and rings. List go`s on.
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im sure Dave had one of them a few years back, restore it then sold it ?
yes i ment the wasting on the Dt125 racer shot.
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Freaky, I was tossing up to buy your MX 360, or Tm a while ago.
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http://www.ebay.com.au/itm/YAMAHA-DT125-DT-125-34X-GENUINE-NEW-OLD-STOCK-CYLINDER-/330738703305?pt=UK_Motorcycle_Parts&hash=item4d01901bc9