Marzocchi Forks MC5 Set-Up

[glowride]

Here's a Q for you tech guy's like Mike Winter, Mike Lenz or Larry perkins, as well as the rest of you aficionado's.
  Are there any differences in the Gray leg (slider) Zoke's and the Gold leg Zoke's (i.e. travel & piston rod flow holes, general performance) or is it just the color?
  Reworking '77 250 MC 5 to have a set of sweptback triple clamps, I have a set of 35's & 38's trips' leg's & all. Looking for '78 Torque pipe (fatter pipe) and someone to rebuild my 13.5" Marzocchi gas shocks.
  All this came about after I saw the '77 400 Moiseev on the 495KTM site about a couple years ago. Anyone notice that it appears to be sporting some hefty travel with those newer forks, ('78'9'80's?) and the fatter pipe? Can anybody tell if the rear shocks are any longer?
  My Main concern is how will this effect the geometry of the bike in general with handleing characteristic's.
  I would like to set-up my machine the same as this, or as close as possible considering my 6'6", 250 lb. frame. Any clue on rear shock set-up especially, would be greatly appriciated.

Thanx, Mark

'77 250 MC5
'82 250 MC

[brian kirby]

Mark,

The gray legs started out greenish-gold but it fades/wears off. It was not paint, but some kind of coating for the magnesium legs, someone here probably knows what the coating was. '77 Can-Am MX-3s had the same forks and most of them have the greenish-gold gone too.

Brian

'72 Berkshire

[Rocket]

I can rebuild your Marzocchi shocks, I have new seals, o-rings etc.
Rocket

[tomale]

I have been toying with swapping out my zokes which are 35 mm for a set of the later models which are 38, they are longer but I think ther are a couple of ways you can deal with it... you could leave them stock and then use longer shocks that keep the fork angle the same. or you could push the fork tubes up into the triple clamps to return them to stock. what I do not know is if there will be a problem matching the them to the steering head.. some bikes use tapered bearing and the 76/77 uses ball bearings...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[tofriedel]

To the best of my knowledge, ball bearings were used throughout the 1981 models with Marzocchi forks.  1982 models used tapered roller bearings.

Tony

[Mike Lenz]

I believe the forks on the 77 400 are 78 model 38mm, or maybe even 80 models.  The longest you can go in the rear is 14 inches due to engine clearance. Even at `14 you may need to do a little more grinding on the engine. It is ground there at the factory some already on the mc-5's. Make sure you have 14 and 1/8 inches bolt hole to bolt hole after grinding so arm will never hit engine from loose shock bushings. Be careful this is already a weak point from the factory grinding and can crack if engine run with loose mounts at all. You dont want to take out much more, but 14 inchers can be made to work alright. Just make sure your getting more shaft travel with your 14 inch shocks over the 13,5 inch, or your gaining nothing. The pipe on that bike looks to also be a 78/79 OEM with an aftermarket rear end. 79-82 front wheel and he made the rear brake a full floater. You need to avoid raising up the front of the bike much more than the rear. You can do this by sliding up the forks and if not enough put a spacer above the top out spring on the damp rod to limit travel. 78 and 79 forks didnt work real well. To fix this use "fluted" 80/81 damp rods. Terrycable and Hi Point also made kits for the 78-79 forks. That 77 is basically how I have my 77 set up, only I stayed with 13 and 3/4 inch shocks and limited the forks to 9 inches travel.  I am building one for my son this winter where we will be going with 14 inch shocks and as much travel up front as we can under the guidelines I mentioned above.

[Big Mac]

A couple of '77 MC5 setup notes from a 6'3" 250# guy-

> Stiffer springs front and back are a must, and neither 35mm fork or stock Marzoke shock springs are easy to find. I've got 2" pre-load spacers in front, oil at 5.5" from top and 10 lbs air, 3 bull ring spacers + stiffest preload setting on purple shock springs and 30 lbs air in canisters...front not bad, rear just tolerable. Stickers say 2kg per sq cm, which = 28 lbs/in. Not sure if more pressure could be handled or would help. I may try Ohlins heavier main springs if they'll adapt, probably will need heavier damping too.

> Steering works if you run the forks up though the clamps 1"-1.5" or so, which requires the swept back bar mount...which then cramps long-armed rider position. Tall bars help, as do pegs in lower mounts for long legs. But then the kicker hits the top mount nub which hammers it off the shaft. I filed a notch in the upper mount to act as a flat kicker stop.

> Longer shocks would improve steering, prevent need for forks abve top clamp, eliminate need for swept back bar mount, etc.

> 38mm forks are an improvement, but then puts you out of Historic class for AHMRA or similar class restriction, if applicable in your local club. If you're to go to 38mm, might as well go to better braking of double-leading shoe front brake of '82 KTM 250, to be able to go as deep as the Evo Yamahas in the corner....worthwhile mod as they work fantastic, but takes some fabricating.

Hope this helps.

[Britt Boyette]

After all of that, it might be easier just to get a 82 KTM and call it good. Besides, I saw you race the 77 400 last Saturday and you did really good.

Britt Boyette
1976 125 MC5

[brian kirby]

Just a note, 38mm forks are legal in AHRMA Historic but not dual leading shoe brakes. You can use the later conical KTM hubs on a Vintage or earlier PV bike, but not the dual leading shoe brake.

Brian

'72 Berkshire

[tomale]

my plan is to go with the 38mm forks and then put spacers below the top out springs. I am actually thinking of not using the swept back upper handlebar mounts because it causes you to be too far back over the seat which is not so good for tight corners.. If I have to I may use longer spacers up front to get it to turn better... I have a couple othere ideas for the motor too.. As for the braking, We have a local guy that rebuilds the front shoes and Arc's them so that the really stop well....

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[454MRW]

You might get Bob Wardlow to sell you a set of his trick Billet Custom Machined Handlebar Risers to allow you to slide the forks up in the clamps farther, while maintaining the original forward bar position. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[Britt Boyette]

Here is Big Mac on the mighty 400 MC5 at the Salem Fairgrounds indoor racing. Forks look okay to me.



Britt Boyette
1976 125 MC5

[Big Mac]

They don't call me Big for nuthin'.
Looks like an XR75 under there.

[brian kirby]

LOL! To give a little perspective from the other side of the size scale, here are two of me (5'7" 140lbs) also on an MC5 400.





Brian

'72 Berkshire

[tomale]

Didn't know that something like that was even available....but that sounds like a good idea....

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)