Main engine bearing question 74.5 and 77

[Gippslander]

Have got 74.5 and a 77 KTM's, both 250's, am about to start pulling the 77 apart to give everything a freshen up new seals/gaskets and a ring, and anything else that needs doing, was contemplating what to do about the main engine bearings, and where to purchase the "special bearings" that come apart and are in three parts, when I see an advert on USA eBay that says:

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The Buzzard Races KTM's also and is always looking for more new replacement parts!

NEW KTM 250 Crank bearings and seals.....I used this when restoring a 1978 KTM MC5 250.....You will find that most of the 250cc Pentons and KTM's use the same 3 Main bearings and crank seals....
....Now if you REALLY must have the original 3 piece bearings that cost almost $70 EACH - go ahead and get them somewhere else!....all the Buzzard's engines don't know the difference!....I always substitute "regular" ball bearings wherever I can - they are the exact same sizes as the originals and go in & work just as well!.....I use the extra money I save to get other stuff!....( Like tires )....
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Anybody know anything about using plain roller bearings to replace the three-piece original bearings, does it work okay?

[Slakewell]

The Buzzard knows his KTM's you may need a spacer if you use plain bearings. I will use plain in my next 77 build.

[Gippslander]

Thanks, sounds like "eyeball engineering" 

[Slakewell]

Not sure it's a 100% correct but you cant get plain bearings the correct width so they need a spacer under them.

[ozktm151]

Used NTN 305E in my 81 250 for awhile with no troubles. They are a flat two piece roller bearing so everything goes back together per original set up. Please check the internal, external and width dimensions just to be sure. You can also get replacement mains from Al Beuhner at Penton Parts for about $90 US last time I looked. The true Penton guys like the three piece because it can be set up just right with shims behind the crank shells to get the correct tolerence. Refer an engine manual for the set up. Hope this helps.

[ozktm]

I have used SKF NJ305 C3 ECP bearings for a long time now from SES bearing supplies in Wollongong. I still set them up as per the manual, in regards to the shims, to guarantee that there is not too much side play available with them.
Using these is easier to obtain and cheaper than the three piece magneto bearings, that we cannot seem to get here. Andre does sell them on his Klassiker website though.
The good thing is you can easily split the cases if required.

I have just rebuilt the bottom end of my 81 495 (rod needed doing), and it too had the NJ ECP type bearings fitted. They were still good, but but as i had it apart and its a quick job, i dropped some new one in.