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

[OverTheHill]

Firko, here's a project for you in relation to T100/5TA motors. Probably mentioned it before but my 'long legged' RT1 frame had--had a 3TA in it when i bought it. Never actually saw it fitted but had to smack the downtubes back a bit with the old farm wooden sledge hammer but looked like no mounts were altered. Funny the things that come back [memory], when i was there at christmas hills in late "67 i'm sure i saw a unit 500 motor in a lightweight metisse frame, looked good too. Like i say--long ago & might be wrong. Cheers. ps, talking tyre pressures on another forum, i recall Tim [Gibbes] with the DT1 straight out of the box & into a muddy mx still with the 19 trail tyre on front, took the valve out & threw it away, put cap on & proceeded to run rings around all of us. psyched us all right out that did!! He knew we were all watching & thinking that'll never work so double psyched us all when it did. [desperate measures that day for the slippery going probably more than mud in hindsight].

[KTM47]

What is the best motor fitted to a dirt bike (motocross).  There is only one answer 490 Maico.  If you haven't owned or ridden one you can't really comment.  When Kawasaki were trying to perfect their 500s they tried to make it like the 490.  Of course the reed valve motor is the best but even the others are great.  If you think they aren't the best then why are there probably more 490 Maicos around now than there were in 1981/2.

Maicos rule

[firko]

The 490 motor is in reality the flow on end result of a motor born in the fifties. The engine is indeed the ultimate air cooled 2T big single and as Kato47 wrote, if you haven't ridden one you can't really knock it. I guarantee that once you do ride a 490 you'll finally understand what all of the hype is about. It's just a shame that Maico was on its arse by 1981 and its demise set for good in 1982 by biased and unfair reviews in the American motopress. It's interesting to find when looking back that the European, British and Aussie mags were far less critical of the '82 model and in many cases wrote that it was better than the '81. But I'm waffling...............imagine what Maico could have come up with if they'd been financially fluid moving along into the 80's and 90's? The next generation 490 engine, the 1983/4 SC500 was so much better than the legendary piston  port 490 but the damage was done and nobody wanted a bar of Maico by then, opening the door to the Honda CR500 era (another great engine).

[KTM47]

Thanks Firko.  Although my bike is a twin shock it is a reed valve motor.  Also which bikes bring the most money when selling.  My guess would be Maico 490s.  You can buy a brand new 490 from Maico only in the UK if you have 9,000.00 pounds.

I also have a 2000 RWJ 500, yes it isn't classic mx yet.  It has a similar powerband to the Maico ie from idle to changing up no real kick, just smooth power.  However it keeps revving where the Maico stops.  Really it is too much for MX.

Also my handle doesn't stand for the bike brand.

Kevin.T.M

[firko]

Thanks Firko.  Although my bike is a twin shock it is a reed valve motor.  Also which bikes bring the most money when selling.  My guess would be Maico 490s.  You can buy a brand new 490 from Maico only in the UK if you have 9,000.00 pounds.

Back in the day I had a twin shock 1982 GS 490 that had a reed cylinder. When I bought it I thought they all had reed cylinders but I soon learned that it was fairly unusual when total strangers rang me asking if I'd sell it. I put a lot of miles into that bike, and even rode it to work every day for a while when I wrote my car off. I eventually had my life changing mega crash on it destroying my ankle and putting me out of bikes for almost two years. I sold it to a young guy in Hawkesbury club who lived in Sydney's Blacktown and never saw it again. Damn I'd love that bike today .

[80-85 husky]

I rode the first w/c 500 maico years ago and found it to be a great engine, soft at the bottom for no hopers like me but plenty of go for the full throttle boys (all 3 of them )

I rode a 250 twin shock recently and it just reminded me of how good they turn in... sweeet

[pancho]

 Seems that this is probably more like a list of personal favourites!
   Largely depending on the 'time frame'
 
 Going back a bit my thoughts go with specials using B31s,  Goldies, Ariels, Compy AJAY Matcho, Norton ES2, JAP, etc. then the freakish XTYamaha.
 
 But of the oldies I think the best built, best looking and sometimes most amazing was the old T100 motor.
 
cheers.

[huskibul]

  I think your right there pancho ! And iam going to put a plug in for the humble BSA unit single - starting  life in 1960-61 as the 250 c15 and going right thru to the late 70's as that pre 78/evo weapon the mighty CCM ! being used very successfully in every dirt disipline  ! including 2 world 500cc mx championships and gold medals in ISDE with Jeff Smith onboard  B40 and B44 in 64' and 65' ! not to mension used by police and defense forces from around the world - Cool little donk the beeza ! 

[farmer58za]

The Yamaha DT/AT/CT/RT motors are the most enduring but for sheer performance and flexibility, I have got to go with the Can Am (Rotax) rotary valve motor. Plonks like a trials bike and top end like a roadracer. Stunning!
Regards
David

[KTM47]

Really if you wanted to name the motor (bike) that has had the biggest effect on Motocross and Enduro, it is the very first YZF400.  It changed dirt bikes forever and maybe not for the best.  The modern four strokes are harder and more expensive to maintain and they are noisier than two strokes.  Right from the first model the YZF400 was 102 DBA from the factory and the YZ250 two stroke was 98 DBA.

Bring back two strokes!!!!!!!!!!!!!

[Paul552]

Really if you wanted to name the motor (bike) that has had the biggest effect on Motocross and Enduro, it is the very first YZF400.  It changed dirt bikes forever and maybe not for the best.  The modern four strokes are harder and more expensive to maintain and they are noisier than two strokes.  Right from the first model the YZF400 was 102 DBA from the factory and the YZ250 two stroke was 98 DBA.

Bring back two strokes!!!!!!!!!!!!!

I had a 426f
Man what a engine but hard to ride.
A art to start also. 1st kick or never!

[JohnnyO]

Of all the bikes I've owned and ridden I'd have to say the 81 490 Maico motor is the best. Smooth broad and strong power delivery it just does everything right.. only negative is they can be hard to start

[geoff]

I've been a member of the forum for almost 5 years and never submitted any posts, but on the prompting of Pancho (Wally) here goe's.
  After watching Dave Curtis racing the big Matchless G80CS in the late 50s and early 60s,against the best in the UK I reckon that the AMC motor takes some beating. It is still a force to be reckoned with in the right hands and having owned several over a very long time still say that they are as reliable and as quick as any other pre 65 dirt motor including the Triumph T100.
                                                Geoff.

[OverTheHill]

yes i'd have to agree with Geoff in hindsight even after plugging for my unit 500 metisse. The AMC [in the open class] could stretch them to 600cc & used to make the ground shake. [probably the motor vibration rather than traction haha]. Keith Hickmans Cheney Goldy opened our eyes down here along with John Burton on the T100 unit Metisse two totally opposite bikes & type of rider--but good to watch, [as they lapped me]. I think the Goldy had a twin plug head with one going in through the side between the pushrods [or did i dream that one], would have to surely be a 10mm honda 50 type plug. Used to run a centre plug in my B33 using a honda 50 type 10mm plug. Cheney would have had to run a twin type mag firing both together somehow?. Anyone know? Anyone old enough to remember?--sorry getting off subject. Cheers.

[Momus]

Okay so I know these don't figure too highly on our current hit parade or "must have" bikes but you can't deny the Honda flat single four stroke motor as fitted to early Z50/70/90 and 110 bikes has probably introduced more people to dirt bikes (and bikes in general) than any other motor ever built.

As bullet proof a motor as ever built and able to withstand years and years of abuse yet still start up and take some more.  Well done Honda   

Bit of a necro hump here but I like the little 'underbone' Honda engines as well; the 50/70's with the points magneto that replaced the C100 pushrod 50/55's rather than the CT90 points on head.

Been made in the 10's of millions  since 1965 and fitted to what I reckon was the real progenitor Honda dirtbike, the SL70.