WANTED: Lower L/H fork leg - 78-80 KTM

[pketchum]

I have an immediate need for a lower L/H fork leg for my 1979 KTM 250 MC which uses 38mm forks.  I'm not sure if the 78 fork leg is the same as the 79-80 models.  I'm planning on racing it at Mid-Ohio in late July.

I spoke with Al Buehener but he only had the right hand fork lower leg.  Any and all help is very much appreciated.


Phil Ketchum
Kansas City, MO

[Chrisbo]

Phil,

My 78 250 has got 35mm Marzocchis so I don't know if they are the same from 78-80.

Cheers
Chris.

[pketchum]

Thanks Chris.  Mine are the leading-axel 38mm Marzocchi forks so the 78 to 79 model year must have been where they changed from 35mm (1978) to 38mm (1979) forks.

I also noticed a hairline fracture at the top of the right fork leg but it's probably been there all the time. So, I could probably use an entire set of forks.

Bob Seymour has a line on a set of KTM forks and is going to check on them today.  It pays to have good friends and people who are well connected.  The POG is really a fine group of people isn't it?


Phil

[Larry Perkins]

78 250 should have had 38mm forks.  

Have you for sure measured yours, Phil?  They looked bigger than 38mm to me at MOVMX.  I am kind of blind though since the shingles attack.

[pketchum]

Yes, mine are definitely 38mm forks.


Phil

[OUCWBOY]

According to the 78 Parts Manual, they used both the 35 mm  and the 38 mm, but it is not specific as to which model had what. The 35's had 250 mm of travel and the 38's had 270 mm which is just a tad bit more than 3/4".

Donny Smith

[OUCWBOY]

Phil,
looked at what I have and I have 2 L/S, but they are both 35 mm.

Donny Smith

[454MRW]

My brother and I both have 78 MC5 250's with 38mm Marzocchis, so I figured that the GS had the 35mm forks. I have a Nov. 78 Cycle World test article on the MC5 which states that the 38's debuted in 78 and recommended performing a modification to the valving to soften the compression damping on fast bumps or jumps, to avoid hydraulic lock and forearm fatigue. The article states that Can Ams using the new Marzocchis received such a modification in their factory in Canada which effectively improved the action. Mike

Michael R. Winter
1974 250 HS-1980 250

[Larry Perkins]

125 and 175 had 35mm and 250/400 had 38mm.

Larry P

[OUCWBOY]

Thanks Larry, that's what I thought too, but just wanted to hear from the experts.

Donny Smith

[pketchum]

Mike,

Thanks for sending me the Marzocchi article which suggested the fork modification to reduce hydraulic lock on square edged objects, or when jumping hard.  I made this modification (add one extra hole at 90 degrees to the original) to my damper rods last night as my '79 forks had only one oil passage like your '78 forks did.


Phil

[Chrisbo]

quote:Originally posted by Larry Perkins

125 and 175 had 35mm and 250/400 had 38mm.

Larry P

Larry is that gospel? as I have a 78 MC5 250 which has 35mm forks on it, or did KTM just throw on whatever they had lying about the factory at the time.
I've not had the bike since new so it's possible someone may have changed the engine for a larger one or the forks and triple trees for smaller ones. I don't suppose there's any way to tell from the frame number what size of bike it was from new??

Cheers
Chris.

[Larry Perkins]

Nothing KTM did was gospel but my memory says as a rule in 78, 79, and 80 small ones had 35mm and big ones had 38mm.  I am just checking out my 79 125 and both have cracks.

Does anyone have 35mm lowers like the orange ones that they wish to sell?  Thanks n advance!

Larry P

[Chrisbo]

Thanks Larry. One of mine is cracked also but I was going to try and get it welded then remachine the bore and groove in it. I thought it was just someone extra rough changing the fork seals that had cracked it but it seems like it's a common problem.

Cheers
Chris.