640 Adv / CS Sprocket / Loctite ?

I'm a licensed mechanic, use a good slather of Blue medium strenght and fold the lock coller tight and your good to go!

nyc gs

You may find in time that you switch back to the stock 16 gearing.

I changed mine to a 15 tooth for about a year and then went back to the 16 tooth. The 16 works much better if there is any open road riding and I have done some tight off road with this 640 torque monster and it's not much of a problem.

JMHO

Well since this thread was started almost 2 years ago I wonder if he even still has the bike.

I am kind of thinking of adding 2 teeth on the back and keeping the 16 tooth up front. Kind of splitting the difference and see how that feels. Any thing other than tight trails, which I don't do much of with this bike, I kind of like the stock gearing also.

OK, it's been a year since this has been on the first page, it's spring, and I'm doin' some annual updates the ol' 2000 LC4E. One thing I'm trying to do is get the gearing right. My conclusion is that it can't be done with the ratio width on these five speeds. I ran the stock 16:42 for one year and liked it generally for distance travel so long as I kept speed at 75 mph or below for long periods. Much above that and my ass got a good vibrating and starts to feel funny (in a bad way) after a while. However, when I get on single track and the tight stuff or climbing hills I get stuck between a too low first and a too high second.

I changed to 16:45 and all is good off road but it dropped my top comfy highway speeds by about 5 mph which I feel is too limiting. So now I'm thinking the best compromise is back to 16:42 for most road work, 15:42 for off road, and throw in a 17:42 and the bigger chain guard for long distance work.

All this switching around makes a new bolt and washer each time unworkable. I read Creeper's and other's advice reccomending a new bolt and washer each time, and the reasoning make sense, but the service manual does not mention the need. I'm gonna go with fresh 243 each time, proper torque, and changing the bolt and spring washer once a season. I'll let you know if my theory ends up being flawed.

im sure if you look you could find the spring washers cheap... I reused one for about 2yrs though

They washer and bolt come as a set for around $5 US. Not bad to switch out occationally but too big a pain for switching around during a trip.

This is the other CS arrangement. A nut with a tab washer, rather than the bolt with the spring washer, and from the parts list from Liferider's posted about his leaky O-ring, you can see the splined washer. I'll be taking mine off as well, as I have the same leak as Liferider. . . . though you'd never know it. I washed it pretty good yesterday.

edit: this thread is 2 years old??? Oh well, at least there is a good picture of the 'other' countershaft arrangement. The information out there really only refers to the bolt. I'm pretty sure this style will not back off or loosen up.

since I'm in the same situation..however I'm going from 15/45 to 16/42 cause it's waaaay too slow for any roadwork...and first gear is unusable at this gear ratio..I've got to ask..is there any benefit to using the rubber washer CS sprocket versus the non rubber one?

bonebag, I hear the rubberized CS sprocket was for drivetrain noise reduction, but who knows?

b-rod, taking that arrangement on and off would also lead to fatigue eventually eh? Bending the tabs back and forth. Plus the spring washer is supposed to transmit some amount of force onto the sprocket to help keep the CS sealed, while also giving the CS the ability to move laterally (I am guessing). I don't know why KTM switched, and if there were any other changes to go along with the change.

sparrowhawk, I would think of the CS bolt and spring washer fatigue would relate more to the number of times it is stretched and released, not the time on the bike. Is there a way to easily measure fastener stretch, or is that only something the engineers do? Maybe an easy way to check the spring washer's resiliency?

Ruduced function of the bolt and spring washer are likely related to the number of times the parts are installed and removed. A CS sproket would only be on the bike until the chain is worn so there shouldn't be any problems from simply too much use. I've no idea if the bolt is a fancy stretch type or not. Many modern cylinder head bolts are like that. Torque the head bolts according to instructions and dispose of and replace if ever removed. I wouldn't expect there is a cost effective way to test either the bolt or spring. KTM used to sell the washer and bolt seperate. Now they come as one part (#59033034044).

I think around 2003 the 640s transitioned to the nut and washer shown in B-Rod's post. None of the other shaft parts were changed so I think the function of the spring washer was simply to keep the bolt in place. The new washer is soft (not spring) metal and available seperately for about $5 US. I would suggest a new one after a couple of uses. It works like a cotter key and will fatigue if bent too many times.

No need to fret, I am going to get a seal, O-ring and the tab washer, as the sprocket has been changed, and the tab washer had been reused. That's all I need is for a cheap part like that to give me grief. I have about 10K miles, should I actually consider ordering the sleeve?? #25, the Casquillo Espaciador. Missed my chance earlier today to get to a dealer to order up the parts. Muh plane broke down, and I didn't get any farther than starting only one of 2 engines.

Regarding the spring washer holding the sprocket to keep the junk sealed up nice and tight, it makes sense, but it just isn't listed in the parts. I'm going to agree with Sparrowhawk, in that it is just there to keep the bolt in place, but with what I have going on, there is a titch of lateral movement in the sprocket, but I'm assuming that it's normal. . . . or it's the cause of my small leak. I'll see. It'll be a few days for sure, and the leak is so minor, I'm not too concerned about it.

Stock is 16/42 and this spring I changed to a 17/40 and it still has enough grunt for the easy trails and dirt roads I ride. But my question is it buzz's so much on the hiway that I don't feel comfortable running at anything over 60 for any length of time, 55 is just about right and very comfortable for me, that's about 5500 to 6000 rpm's. The only sprocket choice left is the 38t rear, has anyone used this combo and how was it on the road (17/38). I have another bike for tight trails and logs s it's mainly dirt roads and pavement on the way there! The more road worth LC4's must have different internal gearing?

Hot,
Did you change the chain protection piece, did you have to lengthen the chain?
thanks, bill

17:40 is a bunch taller than OE gearing. I run 16:42 at 70 all day long and 17:42 cruises at 75+ without breaking a sweat. You should be good-to-go on the tar at 17:40...

ps. the 2003 and later bikes have a slightly taller primary ratio...

bill

When I put a 17 tooth CS on the old girl I did replace the chain protection piece with another. KTM had a specific part for the larger CS.

Having said that.....Bill: How's your travel Blog coming along?

daryl

I have a 16/42 setup & about to try a 40 to drop the revs when on the road , can anyone give me an idea how much difference it will make ?

Instead of dropping two teeth on the rear, a lot of 640A owners keep the 42 on the back and switch back and forth between a 15 and 17 tooth on the front.

I use the 15/42 combo if I know I'm going to be doing 4 wheeler/jeep, slower gravel more technical riding with limited interstate speeds.

Normally I run the 17/42 combo. This is fine for hours on end on the interstate at 75 to 80 or higher indicated, or gravel/dirt roads.

Granted, running the taller 17T front, you won't be able to loft the front with the blip of the throttle, but it makes for a much more relaxed engine at speed. 70 indicated with the 17/42 combo makes for a very smooth, relaxed ride.

The cool thing about this combo is that you can flip the axle blocks 180 degrees depending on the front and the chain slack and axel alignment doesn't change. KTM thought about this very handy feature but not many owners are aware.

Dirty

Thanks for the reply mate , I thought about using the 17 tooth front sprocket but from what I understand I would have to grind some of the casing off to make it fit 0n the 06 SXC .

On the 640A's all you need to do is grind the inside radius of the counter sprocket chain guard less than 2mm. A quick 5 minutes on a bench grinder, instead of buying the Duke chain guard.

Dirty

thanks dirty , if it's only 2 mm to grind off I will give the 17 tooth a go .

micq