Author Topic: Can a DT1MX race in Pre 70 classic motocross?  (Read 1757 times)

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Offline John Orchard

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Can a DT1MX race in Pre 70 classic motocross?
« on: November 01, 2018, 09:50:21 AM »
l have the chance to acquire a piston-port DT1MX, are they classified as a modded '69 DT1?

l could be open to advice & parts :-)

Thanks in advance. John.
Johnny O - Tahition_Red factory rider.

Offline sleepy

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #1 on: November 01, 2018, 10:02:05 AM »
Unless there is a rule change in the wind any piston port DT1 or RT1 has been eligible for many years as they are deemed to be follow on models.

Offline Iain Cameron

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #2 on: November 01, 2018, 05:38:31 PM »
The frame and suspension didn't change as long as its piston port , I cant see a problem . the old rules said square swingarm but that was changed years ago as the RT1 didn't have the square arm . all early DT 's had a DT1 as a pre fix number .Iain
Yamaha tragic ; dt1, rt1, dt2, rt2, dt2mx , rt2mx , mx250, mx360,sc500, 74dt125, yzx125, yzc250, yzc400, yzd250, yzd400, yzh250, yzh80 , dt100 , xr75 ko xr80 03 , it175 82 . Not a member of any club

Offline sleepy

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #3 on: November 01, 2018, 06:41:30 PM »
While on the subject of DT1's, a 360cc DT1(not an RT1) won the pre 70 unlimited class at the Australian titles this year which could be a first.

Offline Bamford#69

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #4 on: November 01, 2018, 07:29:37 PM »
 Yamaha DT1 pre 70 , DT1MX was a new model and like a DT2mX .is pre 75, not a flow on , and not pre 70,
« Last Edit: November 01, 2018, 07:31:42 PM by Bamford#69 »

Offline sleepy

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #5 on: November 01, 2018, 07:58:04 PM »
Yamaha DT1 pre 70 , DT1MX was a new model and like a DT2mX .is pre 75, not a flow on , and not pre 70,

From what I've read on the DT1MX it was a DT1 factory fitted with a GYT kit with lights removed. A DT2MX was a completely different machine to the DT2 Trailer in every way.
Rules just say for follow on models in Pre70 AT1,CT1,DT1&RT1 pre reed block and it certainly falls into that description.

Offline Bamford#69

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #6 on: November 01, 2018, 08:28:50 PM »
yep you are right the DT1MX is  a different model, therefore not a flow on, can you put a GYT kit on a 1969/70
 DT1?

Offline John Orchard

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #7 on: November 01, 2018, 09:15:56 PM »
So how does anyone tell the difference between a DT1 and a DT1MX?  Frame or engine number? Where might l find a list to properly identify what l have? Thanks

lf a DT1MX is a DT1 with a power-up kit, a power-up kit that can be purchased for fitting to a DT1 ...... follow-on in my eyes?

l wonder if the MA rule book goes into this?
Johnny O - Tahition_Red factory rider.

Offline Iain Cameron

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #8 on: November 01, 2018, 10:27:49 PM »
The DT1m shared the same frame as the trail bike . Basically it just had the lights taken off and a GYT kit and High front guard done at the factory . Its still a DT1 non reed .
Yamaha tragic ; dt1, rt1, dt2, rt2, dt2mx , rt2mx , mx250, mx360,sc500, 74dt125, yzx125, yzc250, yzc400, yzd250, yzd400, yzh250, yzh80 , dt100 , xr75 ko xr80 03 , it175 82 . Not a member of any club

Offline Iain Cameron

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #9 on: November 01, 2018, 10:29:13 PM »
1968 DT1
Pearl White
DT1-00101 to 14090
1969 DT1B
Candy Orange
DT1-15001 to 42520
1969 DT1S
Candy Orange
DT1-90101 to 91573
1970 DT1C
Brilliant Red
DT1-50101 to 66389
1970 DT1CM
Brilliant Red
DT1-95101 to 97218
1971 DT1E
Mandarin Orange
DT1F-00101 to 03492   > (Close ratio transmission)
1971 DT1E
Mandarin Orange
DT1F-20101 to 45120
1971 DT1MX
Mandarin Orange
DT1F-90101 to 93684
1972 DT2
Pearl Yellow
DT1F-105101 to 134257
1972 DT2MX
Silver W/Red
DT1F-185101 to 195339
1973 DT3
Competition Green
DT1F-135101 to 163431+
1973 MX250
Silver Dust W/ Pastel   Yellow
364-000101 to 011040
1974 DT250A
Virginia Gold
450-000101 to 031781
1974 MX250A
Competition Yellow
364-020101 to 028497
1975 DT250B
Portuguese Orange
450-200101 to 224381
1975 MX250B
White W/Portuguese   Orange
509-000101 to 007340
1976 DT250C
New Portuguese Orange
450-500101 to 505102
1977 DT250D
Balboa Blue
1M1-000101 to 009399
1978 DT250E
Crystal Silver
1M1-100101 to 112250
1979 DT250F
Competition Yellow
2N6-000101 to 004320
Yamaha tragic ; dt1, rt1, dt2, rt2, dt2mx , rt2mx , mx250, mx360,sc500, 74dt125, yzx125, yzc250, yzc400, yzd250, yzd400, yzh250, yzh80 , dt100 , xr75 ko xr80 03 , it175 82 . Not a member of any club

Offline Iain Cameron

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #10 on: November 01, 2018, 10:30:56 PM »
John did you buy the head and cylinder off Terry from the US .
Yamaha tragic ; dt1, rt1, dt2, rt2, dt2mx , rt2mx , mx250, mx360,sc500, 74dt125, yzx125, yzc250, yzc400, yzd250, yzd400, yzh250, yzh80 , dt100 , xr75 ko xr80 03 , it175 82 . Not a member of any club

Offline Slakewell

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #11 on: November 02, 2018, 08:43:58 AM »
Firko is the DT man
Current bikes. KTM MC 250 77 Husky CR 360 77, Husky 82 420 Auto Bitsa XR 200 project. Dont need a pickle just need to ride my motorcickle

Offline John Orchard

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #12 on: November 02, 2018, 09:41:00 AM »
John did you buy the head and cylinder off Terry from the US .


Yep l did  :-D
Johnny O - Tahition_Red factory rider.

Offline John Orchard

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #13 on: November 02, 2018, 09:45:01 AM »
1968 DT1
Pearl White
DT1-00101 to 14090
1969 DT1B
Candy Orange
DT1-15001 to 42520
1969 DT1S
Candy Orange
DT1-90101 to 91573
1970 DT1C
Brilliant Red
DT1-50101 to 66389
1970 DT1CM
Brilliant Red
DT1-95101 to 97218
1971 DT1E
Mandarin Orange
DT1F-00101 to 03492   > (Close ratio transmission)
1971 DT1E
Mandarin Orange
DT1F-20101 to 45120
1971 DT1MX
Mandarin Orange
DT1F-90101 to 93684
1972 DT2
Pearl Yellow
DT1F-105101 to 134257
1972 DT2MX
Silver W/Red
DT1F-185101 to 195339
1973 DT3
Competition Green
DT1F-135101 to 163431+
1973 MX250
Silver Dust W/ Pastel   Yellow
364-000101 to 011040
1974 DT250A
Virginia Gold
450-000101 to 031781
1974 MX250A
Competition Yellow
364-020101 to 028497
1975 DT250B
Portuguese Orange
450-200101 to 224381
1975 MX250B
White W/Portuguese   Orange
509-000101 to 007340
1976 DT250C
New Portuguese Orange
450-500101 to 505102
1977 DT250D
Balboa Blue
1M1-000101 to 009399
1978 DT250E
Crystal Silver
1M1-100101 to 112250
1979 DT250F
Competition Yellow
2N6-000101 to 004320


Thankyou.
Johnny O - Tahition_Red factory rider.

Offline Bamford#69

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #14 on: November 02, 2018, 11:27:29 AM »
Yes its a pity there is no Official MA site/contact  to get a definitive resolution over eligibility concerns .

Offline sleepy

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #15 on: November 02, 2018, 01:45:30 PM »
Yes its a pity there is no Official MA site/contact  to get a definitive resolution over eligibility concerns .

It is a pity but in this case they would ask 2 questions. Is it a DT1 and is it piston port and with yes to both it is in.
Doesn't maker weather it's a DT1 or DT1B or DT1S or DT1C or DT1E or DT1MX it's still a DT1.

Offline John Orchard

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #16 on: November 02, 2018, 01:49:08 PM »


1971 DT1E
Mandarin Orange
DT1F-00101 to 03492   > (Close ratio transmission)


What's the story with this one?
Johnny O - Tahition_Red factory rider.

Offline Iain Cameron

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #17 on: November 02, 2018, 07:24:41 PM »
It was for Farmers not what comes to mind . It is a nice box of gears though not many around . Congrats on the buy from Terry , John. I will send you a PM . 
Yamaha tragic ; dt1, rt1, dt2, rt2, dt2mx , rt2mx , mx250, mx360,sc500, 74dt125, yzx125, yzc250, yzc400, yzd250, yzd400, yzh250, yzh80 , dt100 , xr75 ko xr80 03 , it175 82 . Not a member of any club

Offline sleepy

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #18 on: November 03, 2018, 11:21:40 AM »
It was for Farmers not what comes to mind . It is a nice box of gears though not many around . Congrats on the buy from Terry , John. I will send you a PM .

Didn't the early 68 models have the close ratio box as well. The parts book shows the from no 38000 there was a whole new set of ratios.

Offline crossedup2

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Re: Can a DT1MX race in Pre 70 classic motocross?
« Reply #19 on: November 04, 2018, 08:32:09 AM »
The best thing about any of the DT1-DT3 and RT1 -RT3 (MX as well) is that all the parts are pretty much available and most are interchangeable (even with later models). However con rods and pistons are different on the DT1.

In the AT1M, AT1MX, DT1MX and other "M or MX" variants they had different ratios in the gearbox, carby, pipe, small changes to cylinder and head. There are other minor changes also which you can find.

I run an RT3 bottom end in an RT3 frame, piston port cylinder, MX250A gear set (fits straight in), YZ250 clutch pack (extra plate), and a YZ400E stator and CDI. It's all pre 70 legal.

If you want the genuine DT1MX you have to chase the case numbers as Ian said. The GYT stuff is like rocking horse poo. But worth looking for just good luck finding it!

Peter B
Anything Yamaha. AT1, CT1 (X3), RT1, DT3 (x3), YZ125X,  YZ250E, YZ400D, IT175E, IT250H, IT490K . Always looking for Pre 78 Yamaha stuff....