OzVMX Forum

Clubroom => Tech Talk => Topic started by: bishboy on April 03, 2013, 12:15:03 pm

Title: CR480 engine in a '81 250 frame
Post by: bishboy on April 03, 2013, 12:15:03 pm
Will a CR480 engine fit in a 81 CR250 frame without any major mods?
Title: Re: CR480 engine in a 250 frame
Post by: firko on April 03, 2013, 12:48:12 pm
Whew :o......When I saw the header I thought you were going to ask if you could fit a 480 motor into a '79 or '80 twinshock frame. We bashed that particular "is it legal for Evo?" subject out of the forum ballpark a few years ago and with all of this RM125-B swingarm, YZ250E legality stuff eating up a lot of forum bandwith lately, I thought the old chestnut had returned ::). In regards to your question though Bishboy, I have no idea but I'm certain one of the Honda scientists on here will know for sure.
Title: Re: CR480 engine in a '81 250 frame
Post by: bishboy on April 03, 2013, 05:43:27 pm
Whew :o......When I saw the header I thought you were going to ask if you could fit a 480 motor into a '79 or '80 twinshock frame. We bashed that particular "is it legal for Evo?"

Changed the topic to avoid any confusion ;)
Title: Re: CR480 engine in a '81 250 frame
Post by: John Orchard on April 03, 2013, 06:18:59 pm
Sorry to be a little off-topic, why couldn't you put the 480 engine in a '80 frame and run Evo?  What rule does it foul?
Title: Re: CR480 engine in a '81 250 frame
Post by: tony27 on April 03, 2013, 06:24:58 pm
Motor is out of a non evo bike, would be no more legal than fitting a 2005 model yz250 motor in a 84 yz to run pre85
Title: Re: CR480 engine in a '81 250 frame
Post by: John Orchard on April 03, 2013, 06:33:45 pm
Ah ok, so another engine can be swapped as long as it is out of another Evo type bike.  Cool, thanks.
Title: Re: CR480 engine in a '81 250 frame
Post by: Stevo17 on April 03, 2013, 06:34:16 pm
I dont know a great deal about the rules but thought that Evo was air cooled, drum brakes and twin shocks? Sounds ok to me
Title: Re: CR480 engine in a '81 250 frame
Post by: mainline on April 03, 2013, 06:37:52 pm
If you are building a bitsa all the major oem components have to be from evo bikes. Better grab a rule book
Title: Re: CR480 engine in a '81 250 frame
Post by: Stevo17 on April 03, 2013, 08:14:05 pm
Isnt an air cooled, non power valve engine from an 82/83 CR480 comparable to an 84 Husky 500 engine and therefore period correct for evo? The rule book is a tad vague and states that modifying newer components to comply is not on, and fair enough. But surely an air cooled open engine already complies and is ok?  The question has probably been gone thru dozens of times on here
Title: Re: CR480 engine in a '81 250 frame
Post by: oldfart on April 03, 2013, 08:29:28 pm
 quote   "If you are building a bitsa all the major oem components have to be from evo bikes. Better grab a rule book"
Or earlier models.
Title: Re: CR480 engine in a '81 250 frame
Post by: JohnnyO on April 03, 2013, 08:35:37 pm
Just because it's aircooled doesn't mean it's Evo legal. You cannot use parts from a later era machine, a CR480 is a pre 85 bike, nothing from it is Evo legal. Read the rules again..
Title: Re: CR480 engine in a '81 250 frame
Post by: Montynut on April 03, 2013, 09:07:12 pm
I dont know a great deal about the rules but thought that Evo was air cooled, drum brakes and twin shocks? Sounds ok to me

All the major components need to come from an EVO legal bike that means that the engine, frame, suspension, hubs and brakes need to come from a bike that is EVO legal. To be EVO legal the bikes has to have all three requirements ie. air cooled, drum brakes and twin shocks / non linkage suspension.

The CR500 Husky engine is legal because it comes from an EVO bike while the CR480 Honda is not legal because that bike is not EVO legal.

Yes this has been done to death
Title: Re: CR480 engine in a '81 250 frame
Post by: mainline on April 03, 2013, 09:09:15 pm
quote   "If you are building a bitsa all the major oem components have to be from evo bikes. Better grab a rule book"
Or earlier models.

Or a tree, you could carve a swing arm from a piece of Oregon
Title: Re: CR480 engine in a '81 250 frame
Post by: firko on April 03, 2013, 09:50:39 pm
Quote
Or a tree, you could carve a swing arm from a piece of Oregon
As long as the finished product replicated a swingarm manufactured from a similar tree grown during the pre 85 period. I think officials could DNA the wood to be sure it's of the period.
Title: Re: CR480 engine in a '81 250 frame
Post by: bishboy on April 05, 2013, 08:29:26 pm
bump....

Can a knowledgeable and wise (and probably handsome and popular with the ladies ;D) honda aficionado answer the original question for a poor kawasaki tragic as I need to know so I can buy a frame this week ;D
Title: Re: CR480 engine in a '81 250 frame
Post by: JohnnyO on April 05, 2013, 09:01:54 pm
I'm thinking it will fit because the '81 250 and 450 had the same shape crank cases and the 480 is basically a bored out 450. Without the radiators on the 250 frame there shouldn't be any clearance problems
Title: Re: CR480 engine in a '81 250 frame
Post by: GT43 on April 06, 2013, 04:13:48 pm
If you are building a bitsa all the major oem components have to be from evo bikes. Better grab a rule book


I gather that it is OK to use cosmetics from a Pre-85 onto an Evo bike?  :-\
As have seen a few "YZ-J" Tanks / seats on "H" models.