Maintenance & Technical > KX500 Original

How Low Can You GO!? (Try 12T/52T!)

(1/4) > >>

kawrider:
Ok, guys.  You're gonna love this.

I'm the new K5 owner who inquired about de-fanging the beast (See Taming the Beast!).  Most folks responded to my inquiry by suggesting I try lower gearing, which I have done.  In my last report, I was experimenting with 13T/52T, much lower than anyone suggested.  In response, many of you said that gearing should make the bike really hard to handle.  (Guy at the shop said the same thing.)

Let me state for the record, that I am not really nuts.  :twisted: I'm simply afflicted with the same strange character traits as most anyone who graduated from engineering school :roll: , namely, I LIKE math and I love experimenting!  The point of the 13T/53T was to get the bike's overall gearing close to the KX250.  It wasn't quite there until I put a 12T on the front!  Now, the K5 isn't suppose to run a 12 on the front.  The stock 520 chain will rub the hub flange around the output shaft.  I fixed that with a Dremmel tool: just rounded over the edge of the case flange (around the seal).  With the 12T/52T, overall reduction in 1st is 22:1, compared to 20.4:1 on the 250. Top gear is 8.7:1 on the 500 vs. 9.8:1 on the 250. So the K5 is still faster on the top side! (I calculate about 75mph at 10K engine speed.)

How does it ride?  We'll the best analogy I can come up with is about like an M1A1.  :shock:  We went mountain trail riding last weekend. This is east coast mountains ("hills" to you folks out west).  Up and down and rocky and in the woods.  It was a blast!  First gear is basically optional.  I rode mostly 2nd-4th.  But on a really tight, rocky climb or descent, it was nice to have that low, granny 1st.  By the way, two other K5's showed up with big rear spockets! So, hey, maybe I am nuts!

Another thing that might surprise you is that keeping the front end down is actually EASIER now than it was with the stock 14T/47T sprockets! It's not true that as you go lower & lower the bike is more & more wheelie prone.  At a point, you get far enough below the ideal engine loading that it will just wind through the gears like a formula-one car and stay down.  Think of it like trying to pop a wheelie on a farm tractor.  You're more likely to get it up in a higher gear than low.

kawrider:
Oh, & by the way, before anyone asks, "why didn't you just by a 250 instead of the 500 & be done with it!".  The answer is, that would have been entirely too sensable.  Hey, remember, I ride motorcycles!  As as group, we bikers are not generally known for our exceptionaly rational behavior.

Anyway, it does NOT run like a 250.  Changing the gearing has no effect on the engine's output power & torque.  I've still got twice as many cubes as the 250!

Besides, the K5 has a much nicer seat.

rhinogrrrl:

--- Quote from: kawrider ---...Besides, the K5 has a much nicer seat.
--- End quote ---


...that's not a seat, its a Lazy-Boy! You're riding a Lazy-boy Rocket... :wink:  or maybe a Rocket Couch... :roll:

Sharc:
Thats funny....Wish I could try it without buying sprockets and cutting chain (and buying a dremel...). I thought 14/49 was crazy....I like it but it could be even lower in the Black Diamond "trails" they have in the mountains (real ones) out here....Might just try a 13/49....

Sharc

Rick:
Might want to be careful with that hub flange, especially if you are running an O-ring chain, as they are a little wider.  The problem is that as your chain and front sprocket begins to wear, it will contact the case more and more, and will eventually rub through your case.  I helped someone (who liked the smaller sprockets up front) address this problem after the bearing was visable from the outside.  Surprisingly enough, I was able to build a new case section using locktite two part epoxy and a custom cut piece of 10 thousandths shim stock (and a dremel).  My suggestion is to stay away from O-ring chains while running the 12T, and keep a close eye on any wear on the case.

Interesting and well written analysis.  Thanks for the enlightenment.

Rick

Navigation

[0] Message Index

[#] Next page