What do you think is the best motor ever fitted to a dirt bike?

[Davey Crocket]

While I'm waiting to get booted out of hospital lets talk about the best dirt bike engine ever made.....I know Firko will love me for this....my preference is the mighty Yamaha DT1 series of engines.......250/360......started life as a non reed valve motor in 1968 in a trailbike and ended up winning the world 250cc championship in 1973, carried on to become the famous reed valve YZ250/360 A/B.....the power more than doubled over that time, reliability was never an issue....has had more "hop up" parts made for it.....is still widely used today.....has been road raced, beach raced, motocrossed, flat tracked, enduroed (hare and hounds), trialed, desert racer, commutered, trail riden....all with great sucess.....I hope I havent forgotton anything.....whats your poison?

[firko]

You said it Joan..And let's not forget that the 360 version was equally as versatile and bulletproof. I doubt that a stronger dirt bike engine has ever been built than the DT1. When Yamaha entered into the dirt bike field they weren't sure of the loads and excesses the engine would handle so they over engineered just about everything. In the years following they gradually "de engineered" their motors to ensure that the secondary spare part market remained healthy. They'd learned pretty fast that they weren't going to sell many spare parts for an engine that was so bulletproof. I've pulled engines apart that have been to hell and back and found the crank and rods to be still usable and still be on original bore. I've never heard of a DT1 gearbox actually failing, only when they drastically lightened the gears for the YZA-B did they introduce an element of possible failure (and even then it was ever so slight). I'm first and foremost a Maico guy but after spending time working on these engines for my various hot rod projects, reckon that Yamaha got it absolutely right back in 1968 with the DT1.

[Rookie#1]

If we're not confining this to just vintage bikes I think the most recent offering of the KTM/BERG 300 2t would have to be one of the best engines ever to fire a shot! Power like a steam train yet could easily be ridden by anyone due to the amazingly linear deliver, it's so smooth it almost feels like an electric motor!!

[Slakewell]

My personal fav is the mid 70's KTM 400 with just a few tweaks it can go from electric smooth to arm stretching missile. The KTM 390 whilst the same CC was a different animal and whilst it is no arm stretcher those that know how to set one up will find the best twin shock motor.
Maico 490 just because they are that dam good. 
 

[Davey Crocket]

See how many photo's of the different variations you can come up with Mark.........they truely are dirt bike royalty...... ...gee, I forgot...didnt they do a farm bike version aswell?....I wonder what the most obscure use of that engine was?...Chopper maybe .....born to be wild!!!-.

[firko]

                                                                                       
                                                                                        My stock DT1           
                                                                                     
                                                                                          Flat track
                                                                                     
                                                                                           Motocross: my 'DT1 from Hell'
                                                                                     
                                                                                        DT1 mega trick hot rod
                                                                                     
                                                                                       DT1 rigid framed flat tracker
                                                                                     
                                                                                        DT1 road racer
                                                                           

[vandy010]

Davey Davey Davey,,,
all this time to think...
hope your doin ok, we'll miss you at Harry'sville.
anyway,
best motor?
i've never really ridden one but the Yammie TT/XT500 donk has gotta rate pretty highly.
there's some real nutters out there doing some amazing things with them from road to hillclimb to sidecars to VMX to commuters to space shuttles... you name it.
and i do like the DT/RT Yammies as well

[Hoony]

If we're not confining this to just vintage bikes I think the most recent offering of the KTM/BERG 300 2t would have to be one of the best engines ever to fire a shot! Power like a steam train yet could easily be ridden by anyone due to the amazingly linear deliver, its not so smooth it almost feels like an electric motor!!

I agree on this for the modern era.

[Davey Crocket]

Yea Vandy, I will miss Harry'sville....and your right about the TT500 style motor....I think it was in production for 20 odd years....and raced in all the forms.....maybe even at Bonneville I think also.....its funny how engines that where designed and built as low power/cost  units end up being some of the best engines ever.

[Rossvickicampbell]

the Honda XR motor (s) were pretty good also?

[asasin]

85 CR500 Loads of grunt but still flexible enough to trail ride

[Rusty]

Not a Yamaha guy, but the Dit1 would certainly be at the top of the list - if shaded, perhaps only by the ubiquitous Sachs 125 engine in the 9 & 11 speed variations .... one does count the neutral between each gear don;t they when discussing these engines?   

[Canam370]

Pick any of the Rotax disc valved engines. Pull clean everywhere, lug happily and still have an MX hit up top. Well made too.
Surprised anyone has put up anything different!

[Lozza]

Rotax 124/244 Began life as a air cooled engines, ended up water cooled with a add on water pump and a cylinder kit. Used by at least 10 different manufacturers. Used in karts and bikes, and being a disc valve engine, were equaly at home mx,enduro or road race. Oh did I mention the HP? Parts still available new from Rotax. Close second Kawasaki 350/250/125 disc valve family.

Modern 05-07 RM125

** Just beat me to it Can Am great minds think alike 

[the stig]

      The DT250 / 360 combo was reliable and popular i had 1 of each
      when they first came out.
      White tank 250 first then a green tank 360..
      But the best bike was the Husky 250 wr and a 360 cr . both early
      70

      The Stig