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
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.
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.
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.
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.
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
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
Yes, in 1979 the old 400 engines were used before the 420's came out.
1979 KTM 400
(http://i52.photobucket.com/albums/g8/BobWardlow/Dscf0236.jpg)
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?
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
(http://i232.photobucket.com/albums/ee220/454MRW/1979KTM400Brochure.jpg)
Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
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.
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
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!
(http://www.ktm495.mxbikes.com/ktm79_1.jpg)
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
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.
Rob, Did you purchase this bike last week in Tucker, GA?
Tim
(http://i52.photobucket.com/albums/g8/BobWardlow/Dscf0329.jpg)
I had these about 3 years ago - not any longer. Today I have two more '79 250's that look just like the '79 400 in the lower left. (same bike in my other picture).
I never have rode a 420 - heard they're a nice engine.
Rob W
just womdering. There was an original owner 79 400 on Atlanta craigs list last week that looked identical to yours. I played phone tag for a couple days, then I didn't hear back. I was hopeful that a POG member ended up with it. It was too nice not to be appreciated.
thanks,
Tim
Rob W, have you ridden it, like actively?
I was wondering how this bike is as a rider?
I actually plan to ride/race it!
(http://i52.photobucket.com/albums/g8/BobWardlow/DSCF0192.jpg)
dirtbike,
We had a 79 GS 400 . Restored it in 1990 and used it for a year trail riding. Ours was easy to start ( the Motoplat was a good one and the Bing rebuilt) and fun to ride even for a small bore rider like me.
I did swap out the front forks to gain a disk brake in the front. We run a lot of water where I live and my riding partners were mounted on 2 , 90 CR250's. I needed the brake to aggravate the Honda guys chuckle chuckle!!! The GS would give them fits even in the tight single track
Like Rob said , much better power delivery than the early 400's.
(http://farm4.static.flickr.com/3161/2991822956_7034173f6c_o.jpg)
John D.
'79 420 (in '81 plastic) up the big hill at Washougal, very competitive in evo class.
(http://blufiles.storage.live.com/y1ph0C1dE8taBqW_Y48Y14Cq72Nnp8hlEcNTCif1HpgArn78on0p22n_lgV2j3PDU-i)
My best post yet. I didn't think the topic would go the way it went. First off Dirtbike would love to send you a pic but I don't know how to put them on the forum. Mine looks pretty much like Rob W's. I find that mine is not very responsive and is lean on the over run whereas my 76 400 is pretty zippy bit pins a little. 79 is aesy to start and 76 has a tendency to kick back every once in awhile. One will get around to checking the port and ignition timing on both. Thanks for posts and piccies.
BILL, I don't think you can really upload pictures in that sense. What you need to do is to find a place where you can upload pictures an create a photo album for yourself. Picasa at gmail for example. It's free of charge and you can create several albums.
Then you need to klick the insert image button right above the "r" in the color drop down list above. Finally you need to past the entire URL (address) to the pic between the start and stop image tags created by the button above.
You can of course mail me at bengt|dot|hahn|at|gmail. c o m
Rob, John and Bill .....
My engine is a 1974 that I'm throwing into the 1980 frame.
Will that mean that I will have a not so good power delivery?
I have a bing but I plan to go for a mikuni VM eventually.
Below, the -81 I fixed a couple of years ago.
(http://lh3.ggpht.com/_OCd9GAuw0CM/SV_y31zAPLI/AAAAAAAACTo/49EkPIkk0s8/s640/IMGP0920.JPG)
Further to this type of bike. Can someone tell me the lenght of the rear shock as I wish to buy some new ones and am not sure of the correct length. I am using 13.5 in but wonder if 14 in was stock.
Cheers Bill
dirtbike,
The early 400 engines had a heavy hit when they came on the pipe.
If it were my bike i would add a Lectron in place of the Bing.
That will smooth out the power delivery and , at least for a guy like me , give faster lap times and or better power for single track lined with trees. chuckle chuckle
In the woods the early 400's were down right scary to ride ( at least for me ) [:0]
john D.
John Durrill. I a kind of expected that. The -81 250 was very pipey and almost exploded once the powerband was reached. I know nothing about no lectron but I think I will go for a Mikuni VM.
I'm very keen about the absolute linear electric powerband of my maico 400. Maybe it's a little weak but it's sweet.
I hope that my KTM 400 will be just as nice but maybe a few ponies more??
dirtbike,
The Lectron is the way to go , hand's down. It will give you a much more liner power band over any other carb out their. Its worth the money . We have 2 175 Pentons with them.
Speedy can get you very close with the right needle setup. They are easy to tune.
Your running enough travel to be in the Historic class right?
For the first gen. KTM engine its as good as a reed " kit " with out the loss of top end.
If KTM could have talked Lectron into building a larger facility and upping production , all KTM engine bikes would have come stock with them after 76.
We have a 5 or 6 page article where the Lectron was installed on several bikes. The work was done by the riders at a test track. The before and after results are noted. We can send it too you if you like.
One of the bikes tested was a Penton 250 i believe , ill have to look and see.
John D.
Bill, shock lengths...the '79 420 I got had the original Ohlin remote reservoir shocks on it, at 15". At the Unofficial KTM 495 site (see links), under Parts Manuals/Brochures, there's an '81 Frame KTM GS/MC '81 manual. In it, it shows the two geometry frame measurements, swingarm pivot to upper shock mount, for '80 vs. '81...believe the '79 is same as the '80. It then shows the different length swingarms in those years, and then the different shock lengths.
John, you see, I'm in sweden and I don't think that
lectron have been around here ever. I at least have never heard
about it, or even seen one.
I'm wondering why these carbs have this effect or why the result come up so different with the same carb. Like I said, the red 400 have a real strong bottom right from idle without any sign of hesitation anywhere. That bike is equipped with a plain old fashion Bing 54. Seems to me that a Bing is able to, so why wouldn't it work just as good on the KTM?
Anyway, I have experience and have witnessed the improvments that a Mikuni can make and I'm positive.
dirtbike,
It not the Bing that makes the engine pipey , its the cylinder porting and pipe design.
short cut to Lectrons web site
http://www.lectronfuelsystems.com/
The article is below
(http://farm2.static.flickr.com/1062/1371265488_81d5b738ee_b.jpg)
(http://farm2.static.flickr.com/1356/1371265374_56a8a57938_b.jpg)
(http://farm2.static.flickr.com/1386/1371265408_465a5fc725_o.jpg)
(http://farm2.static.flickr.com/1106/1370365465_b87c73320c_b.jpg)
Hope this is some help
John D.
Thanks John, very interesting and informative. Yes, I know that the combination of the porting, pipe, compression, flywheel and carb results in either a pipey or a tractable power curve. What's a bit strange though is that another carb, possibly could change all (or most) this all of a sudden, yet the original carb can, on another bike produce very smooth tractable power.
I have no clue as to where I can find a lectron or where I can find parts or help with it.
What do you think of the Mikuni VM 38 which is something that is quite common here?
Contact either Teddy Landers or "Speedy"....they can help you or at least send you in the right direction.
Steve Minor
Wilmington, NC