DT1-MX vs DT-1

[Tahitian_Red]

What are the differences between a '71 DT1-MX frame and the regular '71 DT-1?  Any other major differences with the motors?

[vandy010]

hey Red,
i'd reckon some of the older more wiser guys will be along soon with the hot goss but to my way of thinking the only difference in the frames would be a couple of rego brackets {blinkers/electrics/etc} that a racer would probably grind off anyway.
motors,
more than likely gear ratio's/carby and the pipe at most.
and once again, a racer will more than likely make these changes anyway.
so with all that in mind, for my money, they're the same bike.
but should a concourse/back to stock resto be what you're doing, then i don't know diddley squat

[Freakshow]

i think the Dt1mx was also sold as a proper road bike frame ( not an enduro).  So i reckon its the same but as vandy said just differant brackets ??.........

[firko]

What are the differences between a '71 DT1-MX frame and the regular '71 DT-1?  Any other major differences with the motors?

There's two ways of looking at the DT1MX thing. Some folks built bikes using the GYT kit that was available over the counter. Off memory it included a cylinder, head, pipe, bigger carby, alloy high mount front guard, 21" front wheel, serated footpegs, different sprockets and some more stuff I can't recall from memory. The various GYT components could be purchased separately so most went for just the pipe and cylinder/head and didn't worry about the other stuff. Some of the components are now as rare as chicken lips and worth big money. For instance, I just paid $200 for a damaged GYT alloy high mount front 'guard for my Hindall DT1 project.

Another way was to buy a complete DT1-MX already assembled by the factory. The factory assembled MX bikes reportedly had a different barrel to the GYT unit, apparently the porting was the same but the MX had a chrome bore. The frame was bog stock DT1 complete with the street equipment brackets. Now this is where it gets a bit obscure. Some (many) DT1-MX's had cast iron bore cylinders, I've been told because many of the early bikes had problems with the chrome....the oils of the day being a bit ordinary.
I've been playing with DT1's for decades and I've never seen a chrome bore DT1 or RT1 cylinder, either piston port or reed valve. I tend to believe that the chrome bore was discontinued pretty early in the piece but even my "inside guy" at Yamaha Australia who's been with them since the DT1 days wasn't sure when the change occured. Genuine DT1 or RT1-MX's are incredibly rare. Finding one with the provenance to prove that it's the real deal and not a GYT modded DT1 Enduro is the biggy. I've been told that one way of telling is that the airbox is unique to the MX and wasn't available in the GYT kit but I'm not sure how different it is.

Sorry I can't be more precise Jay but the more I get into these bikes the more of a black science they become. The 'Champion' flat tracker I recently bought from California supposedly has a DT1MX engine so it'll be interesting to see what's inside it.

[Iain Cameron]

Weren't the foot pegs mounted direct to the frame as on the mx /yz not on a cross bar , Or was that the DT2MX ?

[Iain Cameron]

Also I think it had a centre mounted spark plug , Firko will know .

[firko]

Also I think it had a centre mounted spark plug , Firko will know .

The GYT/MX head has a different squish, higher compression and it's centre mounted.

Weren't the foot pegs mounted direct to the frame as on the mx /yz not on a cross bar , Or was that the DT2MX ?

I'm pretty certain the footpegs are mounted the same as on the stock DT1. I've got a pair of genuine serrated pegs and they mount the stocl cross bar.