1979 KTM 420mx

[jon]

I have a nice 1979 KTM 420mx I'm fixing up. It's in very good original condtion,except for Works performance rear shocks. I have fitted it with new correct plastic,seat cover,graphics ect. My question is how reliable were the 420 motors? I heard they had lot's of clutch problems. My main worry is the gear box/tranny,I don't mind doing top-ends but bottom ends is a diffrent deal.Any help on setting up a KTM 420 would be great.I would really like to trade it for a 1977 Penton 400,so to run the older class mx.Thanks

[tlanders]

Dave Withrow is the 420 expert. Chime in Dave.

Teddy

[Mike Lenz]

The 420's are very reliable with one small exception.  There is a thrust washer I'll call it that holds one of the kickstarter gears on that can wear thru and cause clutch problems when the washer breaks causing the bearing to also break up.  This washer resides behind and to the top right of the clutch basket. Check this washer annually and replace when needed and a 420 will out live a older 400.  If you need more I can look up the part number.  Also watch the bearing on that gear.

[jon]

Thanks Mike.