1975 gp250 engine in 1974 cr250 mag frame

Just for reference, the operating section of the AHRMA rulebook.

The exceptions are bikes that are "like design" like the '75 250WR, and components from those bikes. Any other bike newer than '74, even if its essentially identical to the prior model like the '75 250CR, are not legal.

The 250 and up Pentons in AHRMA are full of motors up to 79, they all look the same.

Yes, that is correct. As per AHRMA handbook 11.1.10, eligible like-design 1975 model machine include: Husqvarna 250WR.

Wouldn't identical and like design be synonymous in this case? Would it be legal to take a 1975 250WR motor and change the internal gearing to make it close ratio?

I also know that there are more AHRMA rules that are not in the handbook. At many of the races I've been forced to add spacers to my rear shocks (by the same tech – one of the AHRMA trustees) to reduce the travel from 4" to 3.5" because my bike has the GP swing arm. The second time I told him I didn't see anything in the rule book about this – it says 4". He said if I wanted to stick around for a bit he would go get his auxiliary rule book and show me. This is pre-race and I don't feel like arguing the point. I just want to get into race mode. I would like to look through this document some time at my leisure.

That is true, but that does not mean they are legal.

True. Do bad exceptions aren't made where there is no performance gain but that would open a big can of worms. I'll be on the look out for a 75 WR motor.

put this 76 cr250 motor in my 73 cr450 when the conrod seized up !!!my club woudnt allow it to race !!!

Come down to Devon to race then
We would not have a problem with that at the Dartmouth Classic meeting. May 3rd bank holiday sunday.

I have a 75 wr 250. The 6 speed wide ratio gear box is NOT an advantage in motocross. Too big a gap between gears. I run 10\56 sprockets. It is still gappy. Huskyjunk at one time had spare built cr 250 motors for sale. I have rode the 74 cr back to back with my wr. I like the close ratio better, even in cross country. cr vs wr gear box for motocross. I like the cr much better. If there is a 6 speed cr gearbox, that is the one to get. Jeff

I think if Giley didn't have the radial finned cylinder head, then nobody would have cared / noticed..

Nobody notices the radial head. It was stock one the 75 WR. A lot of guys put the radial head on anyway. Jeff

Just received my 2015 AHRMA handbook. Lo and behold it now states under 11.1.12 Sportsman 250, like-design 1975 machines includes Husqvarna 250CR/WR. I'll sleep better now.

The wording is the same as it has always been. That is a listing of pre-'75 bikes and any "like design" is noted with the year of the last eligible bike, example:

Honda XL175 (up tp 1975)
Kawasaki KX250 (up to 1976)
Maico square barrel and radial (up to 74-1/2)

When they say "Husqvarna 250CR/WR" without a year behind it, they mean the '74 and older. The '75 250CR is NOT a like design and it is absolutely for sure not legal for AHRMA Sportsman class.

From what I'm reading it states: "Eligible like-design 1975 model machines include (see "like design" note below [pertains to Maicos and Bultacos]):
Husqvarna 250CR/WR.

Previously only the 250WR was listed.

Check the 2015 AHRMA handbook.

I did, you are misreading it. The bikes listed are not strictly the like design bikes, they are examples of all bikes that are legal, the like design portion only pertains to the bikes with a year noted after them in parenthesis, which the Husqvarna does not have. If anything, this change means the '75 250WR is no longer considered a like design, but I can tell you absolutely 100% for sure the '75 250CR is not Sportsman legal, it is an Historic class bike. Go to the Historic 250 rules and you will see:

"1975-’76 Husqvarna CR, WR 250 and 1977 WR 250. 1977 Husqvarna CR/OR models
are allowed, with fork travel limited to nine-inches. Otherwise, see GP 250"

The '75 250CR is not Sportsman class legal. Since the '75 250WR is also listed in the Historic 250 rules I would say it is no longer considered a like design for Sportsman.

Like most of the rulebook, the bike listing is not very clearly worded. Another example is the Yamaha YZ250, the '75 MX/DT 250 is a like design, but the '75 YZ250 is the first year of the Monoshock and is not Sportsman legal, but they are all listed in the section below. Like the ML frame '75-'76 Husqvarna CRs, the '75 YZs with the Monoshock are the first of the long travel Historic class bikes, for sure.

These AHRMA guys need to get their $#i* together. The handbook needs specifics.

I agree, the rule book is a mess.

So is that portion of vintage history So much change at one time and not everyone got it going at the same time.