1975 gp250 engine in 1974 cr250 mag frame

putting my 1975 gp250 engine in a 1974 cr250 mag frame. need any advice or help available. my exhaust will not fit the mag frame from the gp250, nor airbox. would like to hear from anyone else who has done the conversion as to what they did. thanks, mike

Good luck with your build, I would like to do the same thing since finding a 74 CR is next to impossible for a decent price. I'm not interested in it being original, just AHRMA legal and kinda trick.

I have a frame now I just need the right donor bike. I think an after market pipe is the way to go but an airbox may be tough.

I posted a reply in the restoration thread, my 74 mag has a 75 6-speed engine, you will need to find a 74 clutch cover and shifter because the 75 linkage style shifter will be too far upward away from the footpeg on the 74 frame. You will also need 74 front mount plates. The 75 wr250 clutch cover, [low shifter], will also work.

yeah-the airbox or airbell is turning out to be a tough item to find. huskyjunk does not have them anymore and have not been able to find used one. I have a mag frame w/swingarm already powdercoated for sale if know of anyone interested. thanks

I thought it was the kick mechanism that was too low that would not work?

The clutch cover and front motor mounts are a must to make it functional and if you want it to look like the original 74 250mag in the MK frame you'll need to use the older style dish air cleaner and 74 pipe.

Theres usually air bells on Ebay but apparently not at this time.

Try Steve at Huskydoggg in Canada; huskydoggg@hotmail.com.

Also John at Vintage Husky may have a used air-cleaner bell. 760-744-8052

As far as the clutch cover goes, the kick starter on the early mags is in the same place as the later model mags its the shift that's lower.

Make sure you get a 74 250 mag air bell, it's smaller to clear the frame backbone.

You're referring to the air cleaner cover (dish) right? The air cleaner housing (what I refer to as the bell) I believe is the same for all MK frame bikes however I haven't had any personal experience with the MK frame 250mag. I'm only speaking from what I've seen in pictures.

The reed valve intake moves the carb further back , the standard 70-74 air bell won't fit between the carb and frame backbone without major modifications. The dish or outer cover is the same for all models.

I see what you mean. I wasn't aware of the tight squeeze. I bet those air bells are rare since they were used only on the MK frames with 250mag engines.

I have seen people cut and re-weld non mag air bells to make them work.

Thanks for the pictures Crash. I've got other projects to work on now so I'll keep an eye open for parts. Maybe a whole bike will turn up.

Just so you know, the '75CR engine is NOT legal in AHRMA vintage racing. Many people do it, but it is not legal and if someone really wanted to push the issue and protest you, you would lose the protest.

I agree, but finding a true 74 5-speed may be tough. It was a one year only motor and getting harder to find every day. Most have allready been vintage mx'd into the ground. 75-76 engines are still out there and could be the difference between having a mag 250 or not. AHRMA will have to revise their rule book if they want to encourage participation.

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Just so you know, the '75CR engine is NOT legal in AHRMA vintage racing. Many people do it, but it is not legal and if someone really wanted to push the issue and protest you, you would lose the protest

As I was told "winners always cheat,cheaters always win"

Dont bet on it, rules are more important than participation to AHRMA.

Is it not? A couple of years back I was visiting with John LeFevre of Vintage Husky. I brought my '74 250CR and my '75 250CR motors and asked him which to freshen-up to use for AHRMA vintage racing. He said the '75 was the way to go as it is grandfathered into the vintage class. He said this is because the '75 is essentially the same as the '74 250WR except for different gear ratios. Despite the different motor nameplate, it is a motor that could have been modded to make a close-ratio transmission if one had a '74 250WR. This would have been a period correct modification.

Major differences: '75 has six speeds, beefier clutch, and '74 is prone to have cylinder wear/fail issues due to the thin strip between the intake ports.

Of course because he says its true doesn't make it so. But I trusted his reasoning when I had to decide on which motor to go with.

I think you mean 75 wr 250, the 74 wr 250 was still based on the 73 cr, which had the older design 5 speed engine.

The '75 250WR is based on the '74 Mag, and it is legal for vintage because even though the engine is different with 6 speeds and bigger clutch, the chassis is the same as a '74 Mag. The '75 250CR engine is not legal because it came out of a model that is not legal for vintage, even though other than the transmission ratios it is basically identical to the '75 250WR.