Messages

1

General Two Stroke Talk / CR500AF update

« on: October 29, 2012, 05:38:33 AM »

Wow Dogger Thanks!! I cant even explain how much you just helped me. It looks as though there is very little structural bearing on the swing arm pivot bolt at the center point of the case. It appears the pivot bolt has contact on the outward portions of the case and also looks like an actual steel collar pressed in to the case so there is no wear.
I'm still going to make a few calls tomorrow and see if I can find a smaller diameter spring at the same spring rate
and provide more clearance, even with it coped.
Thanks again!

2

General Two Stroke Talk / CR500AF update

« on: October 27, 2012, 09:42:17 PM »

I ended up finding a Ti spring from a different manufacturer (RCS), that had the same OD as a
steel spring.  Even with that, I had to radius the case.  To do that, use a grinding disc the same
OD as the spring and run it off the center line of the case, I took off 2mm.  Remember, that
part of the case is not part of the transmission seal, just surrounds the swingarm pivot bolt
passage.  After grinding, hit it with 320 then 400 grit wet sandpaper and finish with WD40
and a Grey or Green Scothbrite pad to return the surface back to normal.

Here's a picture:



dogger

Ok I see what you've done. I'm in the same boat. I 'm thinking of possibly making a longer link, about 2mm, but then I need to mess with dropping the forks and or offset clamps.
I like the idea of coping the case because I dint have to mess with anything and still have a lot more adjustably for chassis set up. How much meat is in the case at that area where you coped it? I'll look at the parts to try and figure it out.

3

General Two Stroke Talk / CR500AF update

« on: October 27, 2012, 03:30:32 PM »

Thanks guys.

What issues have you run in to,or expect to have to deal with?

Aside from the known problems of stuffing a CR500 engine into a CRF250 frame
which are all known and dealt with during the frame modifications, it looks like I
am going to have a clearance problem between the shock spring and the engine
case and between the airbox boot and the shock spring.

Both of these problems are caused by the titanium shock spring.  The spring has
fewer coils than steel but each coil is larger in diameter and the overall diameter
of the spring is about 5mm more than a steel spring - just enough to foul the
case and boot.  Of course the easiest fix would be to swap in a steel spring, but
I'm not ready to take the easy way out just yet.  I can fix the airbox boot/spring
problem by removing the 10mm spacer I installed between the VForce and the
cylinder to boost low end.  I don't have a solution I like for the case/spring yet.

That's the challenge with these projects, and half the fun.  I'll keep you posted.

dogger

Dogger, great build, What solutions did you come up with to run the ti. spring? I'm having the same problem with a steel spring at 5.4 spring rate. Your help would be greatly appreciated.