Yamaha YZ250B & 360B - Pre75???

[Montynut]

The current MOMS lists the Yamaha YZ360B as an acceptable follow on model for Pre75 Is this correct? It makes no mention of the YZ250B just the 360 but does list the DT250B (not cantilever?).

These are the first Cantilever models. I searching the NET and it seems to say the YZ250/360B was a '75 model but I know it was available through a good deal of '74 (well I think it was - long time ago). I know they are very similiar to the YZ250/360A in many areas excluding the rear suspension.

It would have to comply with the 7"/4" suspension restriction if it is eleigible for pre75. How would this be achived?

Not trying to start another 20 page epic just need clarification.

[Nathan S]

You're right.
The logic is basically that they were 1974 models and are therefore acceptable for pre-75.
Rear suspension travel has to be resticted back to 4".
Don't know what the story is with the YZ250B - logically, they're basically a YZ250A motor in a YZ360B frame, and are legal. 

DT250B is 99% the same bike as the DT250A (cylinder head, front brake & hub, and some minor frame gussets are the only mechanical differences).

[JohnnyO]

The YZ250B & 360B are '74 models and legal... simple really. Just restrict the rear travel to 4"

[Montynut]

Thanks Guy's club member asked the question and the MOMS is more confusing than clarifying sometimes.

Now when I think back it went something like this for Yamaha premium MX bikes each year? Disregarding the SC500
'73 was YZ250/360A
'74 was YZ250/360B
'75 was MX250/400B
'76 was YZ250/400C (the canister fork model and only yellow jobby in OZ until this century?)
'77 was YZ250/400D

[BultacoMacca]

I do not know much on Yamaha time lines, so can someone tell me where the 125B(?) monoshock fits into this discussion? I know where there is one.
Mac

[vandy010]

I do not know much on Yamaha time lines, so can someone tell me where the 125B(?) monoshock fits into this discussion? I know where there is one.
Mac

125"B" was twinshock and the same as the 125 "A" just a different colour.
if the one you know of is monoshock, then it's more than likely be the 125 "C".
i don't know when they were released but it's fairly common knowledge that they're pre~78.

[Iain Cameron]

Vandy is right the yz125B was a yzA in yellow same frame and eng no# except as in the mxb to yzc the first no# after prefix was xxx 1xxxxx  . The mono was a 75 model called the C  . hence Yamaha having to use the X to get the line up back in order for the 76 C's . Iain ps there was a mono 125 in 73 but it was a works bike ridden by Hideaki and his brother Tadao Suzuki  in Japan mx series in 1973 .
Iain

[bazza]

ist 125 was 125C

[Iain Cameron]

first public was the 1975 yzc yes . but there were the works bikes in 73 .

[firko]

The YZ250/360B were originally not allowed to race in pre 75 until a guy named Jody Mason challenged the ruling with some solid evidence to show that the B was indeed a factory designated 1974 model. If it had been that they were factory designated 1975 models released in 1974 the commission would have disallowed the bike due to precedents set by other bikes such as the Mk8 Bultaco being released in 1974 but being the factory designated 1975 model.

Ironically, after all of the trouble he went to, Jody Mason never raced his YZ250B.

DT250B is 99% the same bike as the DT250A (cylinder head, front brake & hub, and some minor frame gussets are the only mechanical differences).

The DT400B however is very different to its 360cc A model predecessor so it misses the pre '75 cut.