Calling KTM-420 expert Dave W.

[jon]

I need tips on what to watch out for and any set-up tips for 1979 and 1984 KTM 420's.I plan to ride vintage mx,what the best shocks Works,Ohlins, ect? How about forks Zokes or convert to J-models Kayaba 43mm/wheel.Thanks Frog

[Dave Withrow]

Hey Jon,
    Sorry about the late reply...........this is the first I've gotten to get on this site in about 2 weeks.  As far as things to look for, Mike Lenz is a good reference.  He raced and sold later KTMs.  The 420 is a good reliable motor.  It's only drawback is that it isn't a 495.  It seemed that during a span of 4 or 5 years all the manufacturers beefed up their motors....400, 420, 490, 465, 495, 500, and so on.  I always liked the 420.  I rode one back in the day and I still ride one.  It has a nice power band, and handles really well both at speed and in tight stuff.  I think Mike mentioned a bearing on the clutch side behind the basket that can dissentigrate and get chewed up in the gears.  Other than that buy piston/rings if you find them.  Not that you'll go through them but they're just hard to find and it's good to have a spare.  Porting is ALWAYS a good idea. As for suspension, I have a KAYABA front set up with the forks machined to accept the stock wheel and axle.  I run Ohlins on the back.  I've ridden Works and even Bilsteins(?) and just like the Ohlins better than anything else. Hope this helps.   GO PENTON!
                           Dave

[tofriedel]

Dave,

As far as I know it is not the bearing behind the clutch basket, but the needle bearing on the kickstarter intermediate gear.  The intermediate gear is held on the countershaft by a supporting ring and an phillips head screw.  The screw comes loose allowing the intermediate gear to moce towards the clutch case cover, which tears up the needle bearing and possibly damage other areas in the vicinity.

The fix is to use blue locktite on the phillips screw before it comes loose.  It is item # 98 in the Group 33 page of the parts manual
(PN 560.33.018.000).

Don't ask how I know.

Tony

[jon]

Thanks Tony/Dave- there a place called //www.ozktm.com that I think is making 495/420 pistons and 495 pipes pretty cool site. I have a set of 38/43 mm Yamaha YZ forks that I'll use,but I think I'm going with a Yamaha double shoe front wheel. I too want Ohlins,but there big $$$$$. I have a new rebuilt set of 15.5 inch Maico Costa Corsa from 1981 490. I should sell and put towards Ohlins or rebuild the vintage Works that are on it. My 1984 is pretty trick with up-sidedown WP's with drum brakes is rare.It's a enduro model,but I'll convert it.My 1979 420 mx is almost done,new plastic,seat cover,replica graphics ect.Thanks again