1979 ktm 400

[Bill Campbell]

Can anybody tell me if the x dimension for a 79 400 is the same as say a 76 400. Just checking as I set mine up as per 76 specs and the motor is not as strong as my 76 400.

Cheers Bill

[dirtbike]

There is only one 400 engine (mint). The latest yearmodel
is 1978 I belive. The 1979 should be a 420 with the newer motor.
Anyway, as for the x dimension I have not encountered any info suggesting that there should be 2 different measures.

I suspect though that you have an older engine. There are 2 different 400 engines. One with 81 mm bore and another one with 82 mm bore. The 81 mm bore engine should have 0.051" (1,3 mm).

I am a bit worried and preffer a slightly larger x dim unless
race gas is to be used.

[dirtbike]

Update!!
The x dimension 0.051 (1,3 mm) was taken from an old penton manual but the engine 400 manual says 1,6-1,7 mm for the 81 mm bore 400 (350) engine and 1,15-1,2 mm for the newer 82 mm bore engine.

[dirtbike]

There is only one 400 engine (mint). The latest yearmodel
is 1978 I belive. The 1979 should be a 420 with the newer motor.
Anyway, as for the x dimension I have not encountered any info suggesting that there should be 2 different measures.

I suspect though that you have an older engine. There are 2 different 400 engines. One with 81 mm bore and another one with 82 mm bore. The 81 mm bore engine should have 0.051" (1,3 mm).

I am a bit worried and preffer a slightly larger x dim unless
race gas is to be used.

[dirtbike]

Update!!
The x dimension 0.051 (1,3 mm) was taken from an old penton manual but the engine 400 manual says 1,6-1,7 mm for the 81 mm bore 400 (350) engine and 1,15-1,2 mm for the newer 82 mm bore engine.

[Bill Campbell]

Thanks for the reply Dirtbike. We here in Oz got some 79 400's along with the 420. I just remebered that the bike I restored could have had a new liner put in it but I can't remember the bore at the moment. Thanks for the information. Will keep it in mind when I check and or reset the cylinder.

Bill

[dirtbike]

Bill, can I ask you for a favour?
I'm building a hybrid. It's a 1980 250 with the old style
frame that I'm fitting with an older 400 cc engine. On
top of it all I'm looking for the 1979 look.
I would really love a picture or a couple of such a bike
that you describe.
Is that possible?

See my project here:
http://www.tinyurl.com/ktm400mc

[rob w]

Yes, in 1979 the old 400 engines were used before the 420's came out.

1979 KTM 400

[dirtbike]

Holdonhere......
Is that a bike in stock form?
Tank and all??

I just can't belive this, that's my hybrid I'm looking at!!!!

How did the stickers look then?

[454MRW]

Here is an actual pic of a MC80 1979 400 with the GS80 (Enduro) kit from a KTM brochure that I have. The MX version didn't have the rear frame loop or lights, and used the rear fender like you have, as well as a smaller gas tank. Mike


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

[dirtbike]

Smaller gas tank? Surely the GS model has (oddly enough) the smaller gas tank? It seem on the pics as the MC model (Rob W) has a larger tank.

[Big Mac]

There must have been an early '79 400 version that went into the earlier frame w/ separate rear engine mount bolt from swingarm bolt, such as what the above pics show) and a later '79 420 MC80 or GS80 which used the new style motor and new style swingarm with single thru-engine swingarm bolt.

I have the '79 420 with later style setup and a '79 magazine test article with all details on MC80/GS80 in same dress as here, showing newer motor setup, revised swingarm with sprocket closer to pivot for better chain slack control. Didn't realize there was an earlier setup in 400 size that came dressed same as the first 420.

Jon McLean
Lake Grove, OR

[dirtbike]

Big Mac, I thought just like you that the -79 only
existed with the newer style engine and frame.
Like this picture.
Clearly we're wrong!

[454MRW]

The way I understand it is that the 420 was a later production and the 400 was early, with the same mounting arrangement as the earlier engines with a separate bolt for the swingarm and the rear engine mounting. I actually have a 1979 dated 400 engine. The tank on rob's bike appears to be one of the larger sized Enduro tank. There are 3 different sized tanks that I have seen. One larger tank with screw holes on top for a tank bag, the intermediate sized Enduro tank and a much smaller MX tank. Mike

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

[Mike Lenz]

The 78 book also lists different timing for the newer 68 stroke engine verses the 69 stroke (76).  2.5-2.5mm for the older engine and 2.25-2.3 on the newer engine.  It may be just me, but now that you mentioned it I think the 69mm stroke engines run better.