Print Page - 79 420 KTM

Ihave a chance to buy a 1979 KTM 420.
Would this be a good Evo bike. I have
ridden the Open class most of my racing
life, but usually on Hondas.

Thanks for the help guys........
TB

The KTM 420 was a good open class ride where there weren't lots of killer straights. Then some of the 500s would eat it up. I rode one in the 84 Barstow to Vegas and faired decent. The biggest drawback to making it an EVO racer is that pistons are really hard to come by. Are you sure it is a 79? I did not think they made them that early.

The guy who is selling said it was, so
I checked on the website that I had
posted on POG last night for everyone
to check-out and it looks like the 79
model that is listed there. Orange forks,
triple trees, orange frame etc. That website
has pictures of most of the Penton/KTMs
made by year. I hope people were able to
view it.

Thanks again Larry, I appreciate and value
your responses.

Oh well can't win them all. I was out of motorcycle racing from 78 to 83 racing BMX. So my knowledge lames about them. It is a good day when we learn something.

Hey Tim , Check out http.//www.ktm495.co.uk
There is info on the 495 a very similar bike to the 420. A few pictures of my 495 are there too.
Good Luck,Jeff in Amherst,Ohio - Home of the Penton!-

Jeffrey P. Borer

Thanks Jeff, That's a great website. 123.5
mph into the first turn would be fun......

I was ready to tell you all for a fact there wasn't a 420 untill 1980; seems my memory isn't what it used to be either- I'm looking at a "KTM Motor Typ 56-420ccm" manual, dated "Edition Mai 1979".

Edited by - Heinz Raidel on 08/23/2001 9:39:43 PM

I'm a new member of the Penton Owners Group and have just started monitoring the forums. I owned a 420 KTM that I purchased new in early July of 1979, although the model was MC-80 420. It was a very fine machine that I wish I still owned.

Thanks Heinz and Glenn. Your responses
are greatly appreciated. I am now
hearing that the 420 piston is a rare
commodity. It would be nice to know
if there are some still around before
I make a decision.

Thanks again to all who have reponded.
You've been a big help........

TB

Tim, I don't know how many 420s were made to get an idea of whatever parts were available 20 years ago.

As a curiosity, I searched my basement last night and found the original motor tag that was attached to my 420 when I purchased it. The production information is as follows:

Type 56 420
Nr. 9-5600515
Lfd. Nr. 422
Motor-Prod. Tag: 7,5,79
verbaut am: 9.5.79

I also found the original sales receipt from my dealer. My 420 was ordered May 21, 1979, and delivered to me July 2, 1979. The purchase price was $2,200, plus tax.

Good luck on finding your piston.

Glenn

I have an 83' 495. I wanted an original bore piston for it. I had to send away to england for it. I have heard that the piston is still available through KTM but I think it is one of those things you order and they never come in. I have been to swap meets and have seen a couple pistons for the 420 but that was last year. I have not had a chance to go to any yet this year. Just gonna have to try everywhere but one will turn up someplace. Don't leave any stone unturned... gets exciting when ya actually do find a part.

I'm not sure if or how this relates to the 420s, but last year we had a heckuva time trying to locate an overbore piston for Kevin Lavoie's 1981 KTM390 in time for the ISDT Reunion Ride. I think he found one through Barry Higgins H & H KTM. I'm not sure how the 390 relates to the 420 but my understanding is they were the same engine with top end mods for ISDT class displacement rules..possibly shorter stroke, I don't know. In any event, the piston was supposed to be available through KTM but my local dealer found them to be on eternal backorder and Kevin was lucky to finally find what he needed at Barry's shop. He had the bike at the Reunion Ride last year, it looked gorgeous and it ripped! Hopefully he'll return with it again this October.
Jeff DeBell (who can't wait for the Reunion Ride!!!)

Jeff DeBell

The 420 was introduced in mid 1979 and built until 1984. From 1981 to 1984 it was primarily an enduro model since the 495 was released as an '81 model for MX use. The 390/420/495 had the same stroke, and a nonreed 495 top end will bolt onto the 390 and 420 bottom ends. I believe the cyl. stud spacing was altered to allow the use of a reed valve in '82 for the 495s. I too have found pistons in Europe, although they are getting hard to find there also.

Probably the best thing about the folks in Mattighoffen is that they never have been afraid to change anything at any time in the production schedule; the post-vintage big bore KTMs are an example. The 350/390/400/420 and 495 all shared lower ends and the 74mm stroke.

I remember my older bro's '83 420 as having a very very aggressive power delivery, the 390s and my 400 seem very tame and torquey.

The December '81 reparaturanleitung lists the 390 as being 44HP; the MC420 as being 52HP; and the 495 as being 53HP.

This doesn't mean that Kevin L wasn't ripping on his 390, he probably could rip on anything except an Ossa.

The 79 420 did indeed exist. I have a cylinder and head from one if any one needs it. I had a 1980 420 that was a fantastic bike.The problem with the old KTM big bores is getting pistons. I think the 420 is 85 mm. You can probably get something pretty close to it from wiseco. I got a 92 mm. piston from a watercraft for my 495 from them. The only draw back was pin hieght. A connecting rod from a CR500 combined with stroking it 4mm and lowering the port timing 1.5 mm. makes for a 520 that should be more than reasonably powerful. I would think that you should have better luck with the smaller piston. Good luck.

Penton Owners Group

General Discussion => Penton Talk => Topic started by: tim bowers on August 22, 2001, 04:58:01 PM