Kickstarter tech question -anyone?

[Big Mac]

I'm about to put the cases back together on an early '73 250 which still has the 14mm kickstarter shaft. I heard that the 17mm from later bikes is the stronger setup and the easier replacement kicker to get anyway. So I now have a good 17mm replacement shaft ready to go.

Suggestions needed --- Anyone out there tackle this conversion before? Assuming the consensus is to go ahead with the swap, what's the best way to drill out the cases to best minimize chance of destroying a perfectly good engine? Looks like there's a steel insert in there now and I suppose I need to get through that as well as the softer mag material around it without egging it. Any suggestion on drill size, like maybe 1/2mm over shaft? Anything needed to get the hole to accept an O-ring to keep the oil in the right place?

Any advice appreciated. Thanks guys.
-Jon McLean, Lake Oswego, OR

 

[DKWRACER]

Very good question!!!! How on earth did you wind up with 14mm shaft on a 250 ? Hopefully you have not tried to convert a 175cc to 250cc, more fooooood for thought....

 

[DKWRACER]

UGH, I feel stupid, was 14mm the stock bore for 250/400cc motors, regardless,  never had any failures, with 14mm...or kick starters in general, lucky me???

 

[Big Mac]

DKW- It's definitely a 250. I have 2 '73 250 motors I'm working from to make one good one... 1 is stamped 3/73 and the other is stamped 4/73 for manufactured dates, and BOTH have the 14mm small kicker shafts. I've heard that sooner or later, the small shafts either break or the small kicker breaks, and either way it's a case-splitting problem to correct, as the 14mm kickers are pretty tough to come by. True?

 

[Kip Kern]

If it were me, I would opt for a later set of "73" cases with the large "K" starter set up.  Good cases are getting very hard to find and I wouldn't risk ruining a set that is OK.  If all else fails, put a "74" engine in it with the large starter shaft, just paint it black!  Call Al Buehner for the large shafts or the kick starters, I find the larger ones easier to find!

 

[DKWRACER]

Buenno Kip!!!

 

[Big Mac]

I sure don't want to be the first ever to tackle this conversion w/ my handy Black & Decker drill--so unless there's someone who's successfully pulled this off on their workbenck, I think I better stick with what I've got. I read in the John Penton book that they spent part of one year ('73 apparently?) going out to dealers and correcting the problem on early models, so it must be do-able? Thanks for the feedback. Jon McLean

 

[Rocket]

I have a 250 motor apart and a 175.  the side covers are the same part number.  The 250 case is just drilled out to 17mm and they use an 0-ring to seal the shaft instead of a lip seal.  Should be no problem drilling a cover, just use a drill press and secure the piece that you are drilling.
Rocket
PS
The first 250's came with the smaller kickers, didn't take long to realize they were not strong enough.

 

[Rocket]

Big Mac
I did a little more investigation on the kicker shafts and realized that the inner case would have to be drilled also.  Should be no problem for a machine shop or home mechanic with a drill press and the knowledge to do this.
Rocket