Whats the difference

[maico police]

Early Yamahas are so confusing . Still don't know which is what?
I guess Montesa having two VB models is a lot clearer.....

[Wendell Clark]

YZ-B motor is the last of the old DT1 type, MX-B is the later 'long case' motor that was first seen in the DT-A and MX-A.

From what I have seen and owned , Nathan S is spot on.

[JohnnyO]

YZ-B motor is the last of the old DT1 type, MX-B is the later 'long case' motor that was first seen in the DT-A and MX-A.

From what I have seen and owned , Nathan S is spot on.

yes he is

[bigk]

So is a YZ250B a pre'75 bike or a pre'78 bike?
K

[Noel]

 from 2012 Moms

18.5.4.9 Acceptable follow on models pre 75
a) Honda CR125M1, XL250K1,
XL350K1, MT250 and MT125,
b) Yamaha YZ360B, DT250B,
c) Suzuki TS400 (all).

Interestingly doesn't mention the YZ250B

Noel

[JohnnyO]

So is a YZ250B a pre'75 bike or a pre'78 bike?
K

It's a pre '75 bike.. it was approved for pre '75 years ago.

[albrid-3]

I was race at Accu Park S.A easter week end, South Australian Titles, in 1974 my friend and I went to Pitman on the Saturday and view the all new YZ250 B first of the mono shock they retailed for $1750 dollars that same weekend Dave basham and Trevor Flood where racing them. both 360. I just wanted one so bad, but my wage was $80 dollars a week, so I couldn`t afford one. I was contented
racing my Honda Elsinore 125.

[bigk]

So are they any good? I have been offered one to ride but declined because I thought they were pre'78 bikes, that and not really being a Yamaha fan. Might have re-think though.
K

[albrid-3]

The YZ 250 B and A, that I owned was very nice to ride, and great to look at, I think they are one of the best looking pre 75 bike on the track.

[VMX247]

So are they any good? I have been offered one to ride but declined because I thought they were pre'78 bikes, that and not really being a Yamaha fan. Might have re-think though.
K

Can't say they are a stand out podium taker, at the Classic Nats for the last five years or so..
Excluding the Herbert Brothers   
Could be a change in the wind now with the split Nationals.
cheers US2

[albrid-3]

With the right jockey on board, they are a good unit.

[Nathan S]

Speaking with all the knowledge of someone who has never ridden one:

I think that a YZ-B that's been limited back to 4" of rear travel is a good pre-75 bike, not an exceptional one.

Brakes are great, motor is great, forks are good. And regardless of your opinion on the old Yamahop stuff, the stock shock is very primitive compared to the modern twin shocks that 'every' other serious pre-75 bike runs nowdays and becomes the bike's weakest point.