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

[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.   I'm simply afflicted with the same strange character traits as most anyone who graduated from engineering school , 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.    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]

...Besides, the K5 has a much nicer seat.

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

[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

[kawrider]

Good point about the sprocket wear.  I'll keep an eye on it.  Thanks, Rick!

[jdv500]

thats good stuff,
on that countergear area with an o-ring chain.
 i've changed sprockets to match my terrain here; 13-53... it's perfect for the rocky and rutty climbs and has awesome eng breaking during decents, 1/4 mile long at times. the sweetest granny gear that you don't have to spin like a wildman to get up anything out there. i have very controlled climbs, even while sitting down,,without having to ride the clutch to modulate wheel spin and rpm.
 the best part is i get to use the other gears in the flat trails.., i still don't have room out there for 5th. enjoy, jdv

[jdv500]

then again,
why bother,you don't have to use a 12 t countergear, non o-ring chain? see the chain performance thread. if you don't want to risk the wear in the case. you can always go up in the rear, why risk the close fit up front.? you won't know how bad it has worn after the ride till you spray off the mud, too late.!! i know it's more maintenance but your guarding your case. besides changing the rear gives you the opportunity to inspect and lube your bearings and spacers, 2 for 1 there, rear gear swap and related maint. the web site called gnarlyparts.com offers all the sprockets for our 5's, all the way from 45t up to 60t rear if you want in steel and alum. my 53 t gear got to my door here in 3 days and only $46 total including shipping., jdv

[TomL]

Kool Beans!!!  I run 13/52 and 1st gear is still a little too tall for my taste.  I didn't think you could get any larger than 52 for the rear.  I would like maybe a 55 steel.  I'm thinking the heavier steel sprocket would mellow the throttle response a bit for more traction and control.  Then again, if I have to buy another chain, I might just break out the dremel and put a 12t on the front!!!

[TomL]

jdv500:  I just looked on gnarlyparts site and 53t was the largest I could find.  Are you sure they have larger??  Rocky Mountain has 52t largest.

[TomL]

I bought a 12t and was going to dremel the case.  But when I took off the 13t I saw the chain was already scoring the case a bit.  After comparing the size of the 12t with the 13t, it looks like I would have to grind a full 1/8" into the case completely removing the flange and would expose the rubber seal.  I chickened out!  Would it hurt to expose that rubber seal???  Or would the seal fall out???  Very scary situation!!!  

Kawrider:  Is your rubber seal exposed with the 12t sprocket???

I wish I could just find a 55t for the rear.  Anyone know who sells one that big???  All I can find is 53t.

[Timbowe]

Get a blank and get a machine shop to drill it for you. Should be too much. The blanks are quite cheap too start with. 5c from timbowe.

[KXcam22]

Timbowe has a good point. I forgotten about that. We used to make rear sprockets for old euro bikes that steel wasnt avail.  As long as it has an odd number of teeth it will fit in a 3-jaw lathe chuck.  If I recall a #50 pitch blank is cheap  (<10$).  Here is what I used to do (well my buddy with the lathe actually):

1. Shave the tooth width a touch to fit the 530 chain
2. bore out the sprocket inside to fit the hub
3. use old sprocket as drilling template to drill mounting holes.
4. paint to keep the rust away.

Hope this helps. Cam.

[Timbowe]

Just searching some old pages on this site. Sprocket specialist list a KDX rear custom made in sizes ranging from 38 - 74 tooth in alloy or 47 - 52 tooth in steel.www.sprocketspecialists.com/html/kawasaki3.shtm. Pretty sure that Kdx is same pattern.

[jdv500]

toml,
 sorry for the late post, been jammed up here. gnarlyparts shows evrything up too a 55t in alum,(sprocket specialties brand). it has the wide teeth, thick.fills the whole inner cavity of the link, not just down the centerline, and mud reliefs cut around the tooth ring as well, $39. been running these the whole time i've had the bike with continued great results. jdv