'75 250 vintage legal?

[Mick Milakovic]

I have a '75 250 MC5.  It has the multi-position mounting on the swingarm.  Is it, or is it not legal for the sportsman class in vintage racing?  I have heard stories both ways.

Mick Milakovic
Delphi, IN
765-268-2570

[rob w]

Hi Mick, Your "75" IS legal for sportsman class racing, it is classified as a 74 LIKE-DESIGN as long as you meet the golden rule, 7-inch-front/4-inch-rear, wheel suspension travel requirement. You also must run your shocks in the up-right position. Also leading axle and magnesium slider Ceriani's or Marzocchi's are NOT ALLOWED.
 Mick, you have the ultimate weapon for the sportsman class there. The 75 has a stronger frame and swingarm than the 73 or 74. Rip-it-up!

 

[Mike Lenz]

BUT, If you do actually have a mc-5 with the old swingarm on it it is NOT legal. Ive seen it before. The legal bike has the two different shock mount locations on the FRAME and is a frame breather. If thats what you have it is not a mc-5, but it is legal for sportsman class.

 

[chris richardson]

FYI - If it is an MC5, AHRMA now has an "historic" class and the bike would be very competitive in that class too. I just got the schedule for 2003 and AHRMA has done an excellent job providing "dual" weekends, where both vintage and post-vintage classes run on the same weekend.

Bottom line? AHRMA has a class for any bike with drum brakes and air cooling!

"Chilly" Pepper
(sometimes hot, sometimes not)

 

[Mick Milakovic]

I have the hi-breather frame with 5-position swingarm mounting and two-position frame mount.  If I place the bottom shock mount on the hole closest to the axle it looks like 4".  My service manual states the amount of travel for each mounting position, and the next position says 5.1", so the last position by the axle has to be close to 4". Was the bike featured in "Keeping Track" the "like design" model or an earlier one?  That bike appeared to have lots more than 4" of travel.

I believe the bike does have the 5 speed tranny, but I'm not sure.  My brother bought the bike from Buck Walsworth back in '76, raced it for two years, then stored it in my mother's basement for 24 years.  I recently acquired the bike in exchange for resoring his '74 Jackpiner for him (pretty good deal, I thought!).

The last thing I want to do is show up at a vintage national and get busted for a bike that doesn't meet specs.  But, based on what information I've got I'm going to push forward and restore the bike for vintage sportsman racing.


Mick Milakovic
Delphi, IN
765-268-2570

[Dave Withrow]

Mick,
    AHRMA callls for the rear shock to be mounted in the center hole of a '75 swingarm to be "vintage" legal.  
                     Dave

 

[AndyL]

Mick,
The AHRMA info that was relayed to me matches rob w.  75 is covered under the 74 Like Design clause. BUT shock travel is an issue.  For the rear, using the rear most top mount (verticle) and the rear most bottom mount, not including the 45 degree mount, gives you right at 5" of travel (at least that is what I measured on my 75 Jackpiner and my book shows the 250 and 400 frames are the same) and a spacer on the shock shaft should take care of the 4" rule.

As for the front forks, I was told that the forks with the "blade" cast in on the leading edge of the lowers has about 7.5" of travel instead of the 7" that the previous forks had.  I have not measured, compressed and measured to be sure yet but I will shortly.  If it does come up over the 7" travel limit, I plan to either swap out the forks or machine a bushing/spacer to limit the travel.
Thanks,

Andy

[Mike Lenz]

Mick, fyi I run 15 inch shocks in the rear hole, by the axle and thetop hole on the frame. This way you can run close to 4 inches of actual shock shaft travel which allows for better dampening control plus the bike sits the same as 13.5 inch shocks[stock leanth] layed over at the 45 degree angle. This brings in the front end a little and helps it turn good for mx.

 

[Mike Lenz]

BY the way we bought many pentons from Buck Walsworth back in the day.

 

[john durrill]

Mick ,
 Teddy uses a shock from Progressive that will let you run legal . we got a set just like them for my sons 1975 175 piner
John

 

[rob w]

How did they figure that would work, having six different shock positions and not having to change the spring rates drastically. When you bought a 75 model or later, a GS, did it come with an extra set of springs?

My Hiro came out of Valparaiso.

4 inches is 4 inches.



 

[john durrill]

Rob,
 we gave them the measurements . you use the second hole from the rear. they figure it in and make a shock long enough so you dont screw up the rake on the front.
 it will only have 4 inches like that. you can use spacers to limit the travel also.
 if you go with new progresives then ask for the same setup Teddy got. we did and they work fine.
John

 

[Mick Milakovic]

OK, lots of good information here.  

What I have is a set of Marzocchi's with integral reservoir that came with the bike.  I don't know whether or not they are stock.  Can they be rebuilt and used in one of the above mentioned positions with or without a shaft-restricting spacer?

Mick Milakovic
Delphi, IN
765-268-2570

[imported_n/a]

If I'm reading this right, the Ceriani's up front with the "blade" would be the 200mm travel forks that came in late '75?  And since that's about 8" of travel, are these forks prohibited?  I have a set that I was planning to put back into condition and use on a '74 250/400.  Is there anyone out there who knows that these forks are for sure illegal?

Glenn

 

[AndyL]

Glenn,
I got my info from Larry Perkins and after re-reading the AHRMA book, I believe the info. (my opinion)

The 75 200mm forks would get by on the "like design" clause but would not be legal under the 7" travel limit.  

Two weeks ago I sent an email to AHRMA asking this very question.  Havent heard anything back yet (and I dont really think I will).


Andy