Maintenance & Technical > KX500 Aluminum Frame Conversion (AFC)

Finally joined the AF family!

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68Fastback:
Been riding a 1990 KX500 for 20 something years now and FINALLY upgraded to a aluminum framed bike.  Was thinking of doing it myself with the motor in my '90 but found one somewhat local at a price I couldn't  pass up.

It's a 2005 CRF250R and the engine numbers show the motor to be a 1997 and it was just rebuilt when bike was converted.  I am considering swapping my '90 in because we machined the transmission shaft to accept two circlips on third gear and plasti gauged the dogs.  Motors been nothing but perfectly reliable for hundreds and hundred of desert miles but we' ll see.

Rode the new bike at Cahuilla MX this last weekend and OH MY GOD is it a Cadillac compared to the old school bike!  So smooth, so roomy, so easy to move around on, so agile and so well behaved jumping.

Bike has Scott's stabilizer, Acerbis 2.9Gal tank, Talon hubs front and rear and came with complete set of extra front and rear rims and tires.

Marco810:
Nice looking bike. I'm Getting more inspired to finish my Rmz500

Whats the idea behind 2 C clips on third?

Foxx4Beaver:
Sweet!
I've posted one very similar in the "KX500's" thread for sale....on craigslist.

sandblaster:

--- Quote from: Marco810 on February 24, 2017, 01:53:00 AM ---Whats the idea behind 2 C clips on third?

--- End quote ---

The 3rd gear snap rings are notorious for breaking causing the bike to have two neutrals :-)
Some guys machine a wider snap ring groove to accept a second snap ring.
What I have found is that most bikes with the 3rd gear snap ring problem have other issues that cause the snap ring to fail in the first place.
Worn gear dogs, worn out shift forks, poor shifting habits, and improper maintenance to name a few.
And I'm sure there are a few snap rings that failed because they were weak.
If you have a snap ring fail, get out your service manual and carefully measure and compare your readings for the shift fork fingers as well as the pin that rides in the shift fork drum slots. Measure the slots in the shift drum in several places, especially where there are bends in the slots.
Check out the dogs on the gears as well as the slots of the mating gears.
Likely you will find other issues that caused or greatly contributed to the snap ring failure.  :-o  :-D

One more thing... Any time we pull a K5 trans... we replace all the snap rings and, we only open them just enough to get the ring over the shaft.

68Fastback:
At the time in the mid 90s I was working in a machine shop owned by a guy that rode motocross.  We would buy, fix and sell bikes on the side as well as made some pretty radical conversion.  My bike was one that we were going to flip as it had a transmission issue but once fixed and I rode it I knew I wanted to buy him out of his share.

We tore the transmission down and found thru a measurement and a magnifying glass that the groove the circlips rode in was slightly tapered  like this \/ and that allowed the clip to jump out of the groove and the gear to disengage.  Machining the groove wider to where it was now vertical left plenty of room between gears and two circlips fit perfectly side by side.  

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