'78 vs 79' 250cc pipes

[tlanders]

I bought two baskets cases this last year. The first was a '78 KTM 250 and the second a '79 KTM 250. I rebuilt the '78 in January and of course am still working on improving it, but I did get to race it in Waldo, MOVMX and Marion so far - it is really a neat bike. The pipe was really damaged and at Mike Lenz's suggestion, I sent it off to Dr. Dent to repair. It still doesn't look that good, but it seems to work wonderfully. When I saw the '79 for sale, I bought it for the forks and the pipe which looked to be in good condition. Mike had said that the '79 forks have better dampening than the the '78. When I took the '79 pipe off the bike, it was immediately obvious that it was different than the '78. The exit diameter was '78 - 7/8", '79 - 1&1/8". Biggest diameter '78 - 3&7/8", '79 - 4&1/8". The reducing cone was shorter on the '79 by a couple inches and I'm sure there are other differences that I haven't measured yet. So my question is this - is the '79 pipe a 400 pipe or did KTM make a big change in their 250 pipes between '78 and '79? Barry or Mike (can't remember which) said that the exhaust manifolds were pointed down on the 250's only, the 400 exited straight out like all the vintage bikes. Both of mine were pointed down which would make me believe that they made a big change in the pipes from '78 to '79. So, why did they make the change? Which pipe is better for what? Could the one with the bigger diameter stinger be an enduro pipe? Mike said the enduro pipes look totally different, these pipes look the same until you look at the details. Can anybody shed any light on this subject?

Teddy

 

[Larry Perkins]

Ted, Ted, Ted,

You need a hobby.  You think too much.  Just joking.  If I remember the 78 250 and the 79 250 motors are a decent amounrt different.  However, I may not remember right for sure because 78 is when I go away from motorcycles completely  for about 6 years.  My hiatus began with the statement, "I'm pregnant!"  from my girlfriend.  That's another story, though.  Anyway if the motors are ported different and the frames are different the pipe would be different.  That would be my guess on the why.  

If the 78 pipe works fine on the 78 and it did well at at Waldo just race it the way it is.  Like the old football coach of the University of Texas said once, "We're gonna dance with the one that brung us."

You can use some of that energy getting one of my bikes finished.  Yeah, that' a good idea.  Keep smiling.

 

[tlanders]

My main motivation in this is to replace a damaged pipe with one that is in good condition. The mounting bracket on the '79 is slightly shorter than the '78, but the end to end and the bolt holes at the end seem to be the same. Externally the two engine look the same, same numbering system, etc. You are probably right that the porting is different and that would normally make the pipes different also. Mike Lenz usually can figure out if the cylinders are different or not from his extensive library of Penton part numbers. What say Mike???

Teddy

 

[Mike Lenz]

The 78 and 79 cyl had the same part no. The 80 cyl was different, had the three finger V boost port. Id run the 78 pipe on even months and the 79 pipe on odd months! Seriously th 70,s are when everybody learned ALOT about pipe design. Therefore you could assume the 79 pipe may be better. I have a 81 250 pipe I will check it to see if it is closer to the 78 or 79 pipe. That should tell us something.

 

[Mike Lenz]

Im starting to wonder if you have a 175 pipe on your 78. I didnt measure the center section,but my 78 pipe has the inch and an eight stinger size?? It also seems to be identical to the 81 pipe in sizes.

 

[tlanders]

I have a 175 snake pipe but I'm at work and can't check which year the engine it came on is. I will see tonight if it is similar to my '78 250 pipe. I thought the 7/8" diameter made sense for a 250 since my Carl Cranke pipe on my vintage Hare Scrambler has a 7/8" diameter stinger. I remember when I was looking for pipes for it, the 1&1/8" diameter stinger pipes were not supposed to be as fast as the 7/8" ones, the 7/8' ones were for motocross and the 1&1/8" ones were for torque. That's why my first thought was that the '79 pipe with the 1&1/8" stinger was a 250 GS pipe and my '78 pipe with the 7/8" stinger was a 250 MX pipe. I believe I will find my 175cc pipe to be a lot smaller in the mid section than both of these.

Teddy