MC5 or GS6??

[Danny Metz]

Hello folks,

I have a 1978 KTM that I have owned for almost 10 years.  I restored the bike to ride in 95/96, but now have some questions about its real identity . . .  The bike is definitely a 1978 model 400 (serial #'s confirm it), but I am questioning whether it is an MC5 or a GS6.  The bike was completely decked out in MC5 decals when I got it, but it has several things that make me wonder.  One, it has a 6 speed transmission, and after looking at pictures of other MC5's, I believe has a GS6 fuel tank.  Also, the Motoplat igniton has lighting coils . . .   So, what other ways can I use to determine what it REALLY is??  Thanks!  

Danny

[Larry Perkins]

Danny

I think the frames were different like in 77 but someone like Mike Lenz could confirm this.  The MC5 if I am right has three smaller tubes underneath the gas tank and the GS6 has a breatherplate with holes welded across this area so that it breathes up under the tank whereas the MC5 breathes from the airbox.  This was true in 77 and I think 78.  Perhaps Mike or the like will confirm or deny this.  I left motorcycles for about 5 years to the lifesong tune of 'I'm Pregnant' as the 78 models were coming out.  

A couple of differences I am sure of are  the larger more flatside tank and bolt on frame loop in the back of the GS6.  Both of these things were easily changed however.

Larry P

[OUCWBOY]

Danny,
 I don't know the answer to your question, but I just thought you might like to check out this web site. Lots of good photos to look at.

http://web.tiscali.it/ktm70pages/



Donny Smith

[rob w]

Danny,

You have a MC5.
The GS6 model existed only one year, 1977.
In 1978 KTM made the MC5 be both, MX and C.C.. The "Cross Country/Enduro kit" was extra $'s and included a 3.5 gal C.C. tank, Speedo, Trapp spark arrestor, Preston Petty headlight and rear enduro fender. Otherwise the same bike in MX trim had a 2.4 gal tank. How ever it was dressed, it was still called a MC5.

Bob

[OUCWBOY]

Never ever would I want to disagree with anyone on this site, but there are 1978 bikes with GS6 decals on the side panels, as well as the MC5. No disrespect intended Bob. That, and the lighting kit maybe the only differences, but I have seen a 1978 that was called a GS6. These can also be seen on the afore mentioned web site.

Donny Smith

[tmc3c]

Hey Guys , Was there a 6 speed MC5 made also? I thought MC5 were 5 speeds only.

Thomas Carmichael

[Dennis Jones]

I have a 77 GS6 with a very large high breather backbone. None of the other model fuel tanks will fit this bike and unfortunatly I need one. It also has a rear frame loop that is welded on instead of the bolt on style.

Dennis Jones

[Larry Perkins]

The 77 loop was welded but the 78 had a bolt on.  There definitely were 78 GS6 models.

Larry P

[tomale]

Just to confirm a few things since I have both a 76/77 MC5 and a 78 MC5 both of which the top tube are the same. There have been other postings as to the difference in the 77 models that the frame was different for the GS than the MC5. Actully I think some MC5's did come as 6 speeds. So I can see how the 78 could have come out as either a GS or a MC5 depending on the trim. My 78 is a 5 speed. I am not sure about the lighting harness on my 78 others have written about the fact that theirs came with a lighting harness but both motors are for the most part the same. I am sure that what others did not mention is the fact that both motors came as 6 speeds... it is just that on the motocross model first gear is blocked out. this is true to all of the silver motors and I think maybe the black motors too. I have been told that the 79 motor was the same too but I can not confirm that. The black motors had some internal differences like a different shifting drum and the kickstarter shaft was smaller. I am unsure if they came as 6 speeds or not. It is possible to change from a 6 speed to a 5 speed and  vise versa this can be done very easily with out major changes or expense. you need to pull the center cases apart and then either change or cut a pin in the shifting barrel. No damage is done and it can be changed back if you wish. I say this because some one before you could have turned it into a 6 speed.
This is one of the true strenghts of our bikes. the bike is truly diversable. Set it up the way you want to.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
78' 400 MC5

[wahale]

In 78 I bought a new 175gs it had 6 gears,oe ktm headlight,not pp,and what we around here called a high breather frame-air intake was under the gas tank.

[Big Mac]

Danny - not like you need more opinions or "experts", but... Bob's theory of one 1978 model/2 formats and maybe even 2 sticker kits makes sense for 1978. I have a 1977 MC5 and a '77 GS6 project bike, and there are definitely way different frames between the two, with the GS6 having the wide rounded "breather-frame" backbone under the tank, connected to the airbox, while the MC5 has a small square-tube backbone and isolated air box. Other GS6 differences are the welded rear loop and different bar mounts on top triple clamp, on mine anyway. The MC5 I have came to me from the guy who bought it new and says it was never modified, and it definitely has 6-SPEEDS...go figure. Also both have 5 wire Motoplats, although the MC5 wires dead-ended into the wiring "block" up under the tank. If yours has MC-5 stickers, 6 speeds, flat side tank, and the non-breather skinny backbone, I'd vote that you have yerself a MC-5 there with a granny gear and a bit further roaming range than usual. Both good traits in my book.

[Young Ted]

Dennis - I have an extra tank that has been repaired many times but would not hold up for enduro riding. If you're interested, e-mail is [email protected]

Young Ted

[Danny Metz]

Hi guys,

Thanks for all the replies!  My bike has a one piece welded frame, but I am still a little unsure of what the top tube looks like.  It has been many years since I had the tank off .. .  But I can tell you the bike breathes through a separate plastic breather box that mounts in the frame behind the carb.  It connects to the carb with a short rubber hose.  The wiring from the Motoplat does terminate in a wiring block under the fuel tank.  

A couple of things that weren't mentioned:  In the manual I got from Alan Beuhner shortly after I got the bike, it says the 400 engine is available in 2 different configurations.  The GS and the MC (according to the manual) have a different bore and stroke. The GS has a 1mm smaller bore, and a 1mm longer stroke than the MC engine.  If this is true, I can easily measure the stroke . . .  And the other question:  Did the MC5 and GS6 use different seat/rear fender attachment?  Does this have something to do with the bolt on/welded on rear frame loop?  FWIW, my bike has the stubby plastic rear fender bolted to the seat.  Thanks again for all the expertise!