2003 KX250 chain keeps getting loose

svttodd · May 16, 2005

I have a 2003 KX 250. The bike is fairly new, and has always been maintained. The bike has a 7oz. flywheel weight, and a Pro-Circuit pipe, the gearing and chain appear stock. Chain is in good condition. Now...on to the problem...

The chain seems to get VERY loose after a whole day of riding in the woods/sand (fast sandy Florida trails). I tightened it according to the book, and I keep it clean and lubed. The chain will get so loose, that it will make a 'clack' sound while riding (especially whoops and jumps). When it gets loose, I can pull a lot of links off of the rear of the sprocket with my hand. I am fairly mechanically inclined, but I cannot see any particular part that seems to be making the chain get loose (no sign of axle block movement). Is the chain really stretching that much (every ride), or is something else getting loose and loosening the chain? Is my riding style stretching the chain ? Or is something else wrong? I have heard that the stock chain is junk, is this why people say that? Help me keep a tight chain. Thanks. -Todd

DWreck · May 16, 2005

Sounds like you need a new chain. Stockers don't last long regardless of your maintenance practices. You get what you pay for. I have had the best luck with O-ring chains but if you ride in sand all the time it might not be the hot ticket for you.

YZ165 · May 16, 2005

Pitch the stock chain, then go to http://www.best-motorcycle-chain-lube.com/ for a new chain and some good lube. Jaybird should be able to set you up with just what you need for your particular riding needs. Hope that helps, YZ165

NacNac250F · May 16, 2005

If your riding a lot of sand get an o-ring chain. Their sealed so the sand and grit can't get inside the chain and wear it out fast. Your probably able to pull the chain off the rear of the sprocket not only because it's loose but also because the sprocket is bad. You can pull the chains off the rear like that when the sprocket is bad. The stock chain and sprockets wear out fast especially if your riding in sand. Invest in a good x-ring chain and those sidewinder sprockets i'm pretty sure come with a lifetime garuntee so check them out. If you replace one thing everything has to be replaced, that means fchain and sprockets.

Camstyn · May 17, 2005

Make sure that your axle alignment is right, sometimes the casting marks in the swingarm are wrong. The best way to measure is from the swingarm pivot bolt to the axle, or use a straight edge and line it up with the rear sprocket, and see if it follows the chain perfectly straight.

Chains will stretch faster in sand but yours does sound a bit excessive, are you measuring it correctly when you set it? It is best to leave it a little bit on the loose side when riding in sand or mud.. And if your sag is not set correctly it can play a role in chain slack as well.

I've had good luck using Maxima Chain Wax, it does not attract dirt like the heavy oils do. The best time to lube your chain is after you wash the bike, take it for a little ride to warm up the chain and then apply. FWIW I've got 7 hours on my KX and have only had to tighten the stock chain once so far, but I don't always ride in sand.

svttodd · May 17, 2005

Thanks guys. The thing that seems wierd to me is that the sprockets seem to be in perfect shape. The chain looks good too (clean, oiled, no obvious wear). After tightening, I check the slack with the bike on the stand, then sitting up, then with me on it an all seem 'ok'. Then after about 20-40 m iles of trail riding (according to my buddy's KDX) it is so loose that it 'clacks' on the swingarm, and you can pull it way up off the arm, or you can pull several links off the back of the sprocket. I will check the alignment, but I think it is good. I guess I just need a new chain and sprockets.

If my suspension is not properly adjusted could it really make the chain stretch that often/that much? I noticed that the suspension seems harder at both ends lately. I really get beat up on the whoops (like a jack hammer). It seemed to be adjusted correctly before, now it seems very harsh. Maybe it's because I am riding more agressively/faster that I notice the harshness, or maybe something is out of whack. Keep in mind that this bike is in very good condition overall, not some clapped-out bomber. I will be tinkering with the chain, sprockets, and suspension settings. Any opinions/observations will help. Thanks. -Todd

fatherturtle · May 17, 2005

I have a 2003 kx and I say tinker the darn chain to the trash. I ran mine for a month before I **** canned it. I replaced my chain early in the bikes life so I wouldn't have to replace the sprockets. I got a x chain from parts inlimited and I have only had to adjust my chain twice after I installed the x ring. If your sprockets are good enough throw just a new chain on it. Make sure the sprockets arean't too far worn though. Also depending on your weight respring the bike to your weigjt and change your fork fluid and shock oil. My bike used to beat the hell out of me until I went up to a .46 (I weigh 190)in the front and stock in the rear.I put 5wt in the front and this bike is totally awesome. I also noticed that the manufacturer didn't put enough fork oil in the bike. I think the manual specifies 1.5qt or somewheres in that area. I removed 1qt. Hoped I helped in a hurry got to go to bed :cool: .

viking20 · May 18, 2005

Change the chain in time and you can easily run 2 or 3 chains on the same sprockets.
If you dont feel sure about how tight the chain should be , remove the shock and pull the rear wheel all the way up.
When the suspension is all the way up , the chain should be almost tight. A lot of people run with a chain that is too tight , and the chain acts as an " extra shock"
Very hard on wheel bearings , gearbox axle bearing , and off course the chain itself.

89kdx200rdr · May 18, 2005

"If you dont feel sure about how tight the chain should be , remove the shock and pull the rear wheel all the way up.
When the suspension is all the way up , the chain should be almost tight."

this is crazy. why in the hell would you do this. if the shock is off the bike how is the "suspension all the way up"?. the swingarm may be all the way up. anyway with the shock off and the swingarm up all the way the distance from the center of the front sprocket to the center of the rear sprocket would be shorter. its an arc.

bikepilot · May 18, 2005

It makes perfect sense, the distance from the center countershaft sprocket to the center of the rear sprocket will be the greatest when the swingarm is level (assueming that the countershaft sprocket is in line with the swingarm pivot). With the rear suspension unloaded, the chain will feel loose, but when you compress the rear suspension it will tighten because as the swingarm gets closer to level, the rear wheel moves away from the counterhaft sprocket. My guess is that you are adjusting your chain too tight, when the suspension compresses it is putting tremendous stress on the chain, causing it to streach. This would also explain your poor suspension performance. I would recomend replacing the chain with a good 0 or X ring unit and replace the sprockets with either hardened 7075 aluminum or steel sprockets. Then adjust the chain so that it has 1/2-3/4" of freeplay when its at its tightest, that is, when the swingarm is level and the chain is at its tightest point (chains are not exactly uniform in length nor are sprockets exactly round).

good luck:)

Rider 007 · May 18, 2005

It makes it easier to find the point of maximum tension in the chain and because the chain will touch the top roller and create tension in it as the wheel swings through its arc.

The 92-93 CR250's benefitted from a smaller top roller to reduce the tension at this point. I've personally seen the cases break where the countershaft was pulled too hard from this condition.
Jeff Stanton's 92 SX bike had an outboard bearing mounted to the frame at one time to help support the C/S until they figured it out.

:ride:

viking20 · May 18, 2005

89KDX , if we had sprocket and swingarm pivot at the same position , the chain would have the same stretch no matter how far up/down the swingarm is in its travel.
The further the sprocket is from the swingarm pivot , the looser the chain has to be when there is no load on the bike.
removing the shock simply allows you to raise the back wheel to the top without force , and check how tight the chain becomes at the limit of travel...
Lots of people run with a chain that is way too tight , overloading chain , and countershaft/wheel bearings.
Imagine the shock through all these parts if the chain is too tight on landing a big jump?
Bikes are not equal either , most people have to run a chain with more slack than they are used to , when riding a KTM ..
And yes , a chain that is too tight will affect the rear suspension in a negative way.

AARONA · May 19, 2005

stock chain/sprocket are garbage.
I recommend vortex sprockets and RK X ring.
Been using then for 2 seasons now, super strong and no adjustment from the initial stretch.
And I am hard on them.

CK · May 19, 2005

I knew a guy that ripped his countershaft out of his RM because he tightened the chain too much...

It was a fairly new bike too... At least it was.

Jaybird · May 19, 2005

My bet is the adjustment procedure needs looked at.
Make certain you have a straight like from the CS thru the swingarm to the rear sprocket. This is the tightest point that the set-up can obtain. 1/2"-3/4" slack at that point, as mentioned before.
Do it this way one time, and check to see how much room there is once the bike is back together and on the ground. This way you can check your chain tension any time you are out riding.

The sag of your suspension has nothing to do with your chain tension.

People are far to quick to blame the stock chains. They last far longer than folks say they do. It's just that many don't adjust or maintain properly.

Titanium sprockets and 200$ ring chains are nothing but a bandaid for the problem.
A man who properly maintains the equipment will have as good of luck with aluminum sprockets and a 30$ chain.

Camstyn · May 20, 2005

Wouldn't a too-much-sag setting cause the chain to run tighter than intended? I thought it would but the difference might be miniscule.

Studboy · May 20, 2005

Ha ha $200!!!! I buy a whole set for $60!!!

DID Standard Chain: $24
Steel Front: $6
Alum. Rear: $30

Jaybird · May 21, 2005

Cam,
The chain only reacts to the swing arc of the swingarm. Since it is not hinged in the center of the CS sprocket, the tension changes throughout the travel. The shock only restricts how fast the swingarm moves during compression or rebound. No effects on the chain drive tension.

Now, a chain drive can help to absorb some shock load. When landing a jump with the gas on, the forward momentum of the drive will absorb more shock than landing with the gas off. But this is simply a physics thing, and chain adjustments don't effect it. Unless of course the chain is too tight.

fatherturtle · May 23, 2005

Jaybird said:
My bet is the adjustment procedure needs looked at.
Make certain you have a straight like from the CS thru the swingarm to the rear sprocket. This is the tightest point that the set-up can obtain. 1/2"-3/4" slack at that point, as mentioned before.
Do it this way one time, and check to see how much room there is once the bike is back together and on the ground. This way you can check your chain tension any time you are out riding.

The sag of your suspension has nothing to do with your chain tension.

People are far to quick to blame the stock chains. They last far longer than folks say they do. It's just that many don't adjust or maintain properly.

Titanium sprockets and 200$ ring chains are nothing but a bandaid for the problem.
A man who properly maintains the equipment will have as good of luck with aluminum sprockets and a 30$ chain.

I take excellent care of my bikes and I tore up a stock chain up in less than a month. They are junk. I am still running stock sprockets and an x-chain and now the drive chain is maintenance free. 3yrs on stock sprocket and a cheap x-ring from parts unlimited. I am a believer of junk hadlebars and junk chains. I am also a believer in the lowest bidder wins cheaper the better in the manufacturing business.

Jaybird · May 23, 2005

fatherturtle said:
...now the drive chain is maintenance free.

Is this statement in keeping with "excellent care"? Because there are no maintenance free chain drives in existance. Only the mis-perceptions of such.

If stocks chains are junk, why is it that some folks get a decent amount of service out of them, and others don't?
I could tell you exactly why, but it's a bit like: :bang:

fatherturtle · May 24, 2005

I agree most people neglect there chains. I also think that certain brands of bikes and years have substandard chains and parts in general. Yeah maybe people have problems with non oring chains because of maintnance issues. I know I could take my stock chain with perfect tension, lubed with chain lube and run a twenty mile enduro course and the chain would be loose. So should somebody stop half way thru an enduro course and lube there chain? I have an x ring no adjusting the chain and I lube my chain before every ride with stock sprockets. Just seems like a cheap investment to me. I have too many other worries than to worry about my chain.

Jaybird · May 24, 2005

Some lubes are on the top shelf of many dealers and shops, and one would assume they would have to be great products. But the truth is that many of the conventional lubes, that are the best sellers for bikes, are so thick and gooey that they may not even pentrate to the friction areas before they set up. Leaving you with confidence that your chain is lubed, when it only has thick goo around the outer surfaces of the chain.

And what sort of time does it take to lube a chain? I can slosh on chain lube in about 30 seconds if I'm in a hurry.
Do you not have to refuel after at least the halfway mark of an enduro? (I know squat about enduro riding so maybe not)
Wouldn't that be sufficient opportunity to ensure that your chain has been lubed...that is if you are using a lube that actually works. With some lubes, the last thing you would want to do is apply it after the chain is dirty. Then you have nothing but a grinding paste to help eat things up.

On worrying about your chain...I have to agree that worrying about your chain should be the least of your worries during a ride. But, there are far more problems that can occur during a ride or a race with a ring chain than with a standard. With a standard chain you never have to worry about the rings being torn by something on the trail, and you never have to worry about if the rings have been sufficiently lubricated so they do their job in the future.
But, I will grant you that if luck prevails, a ring chain will serve you fine. -And should be used if there is muck and slop involved.

fatherturtle · May 24, 2005

:laugh:

Jaybird said:
Some lubes are on the top shelf of many dealers and shops, and one would assume they would have to be great products. But the truth is that many of the conventional lubes, that are the best sellers for bikes, are so thick and gooey that they may not even pentrate to the friction areas before they set up. Leaving you with confidence that your chain is lubed, when it only has thick goo around the outer surfaces of the chain.

And what sort of time does it take to lube a chain? I can slosh on chain lube in about 30 seconds if I'm in a hurry.
Do you not have to refuel after at least the halfway mark of an enduro? (I know squat about enduro riding so maybe not)
Wouldn't that be sufficient opportunity to ensure that your chain has been lubed...that is if you are using a lube that actually works. With some lubes, the last thing you would want to do is apply it after the chain is dirty. Then you have nothing but a grinding paste to help eat things up.

On worrying about your chain...I have to agree that worrying about your chain should be the least of your worries during a ride. But, there are far more problems that can occur during a ride or a race with a ring chain than with a standard. With a standard chain you never have to worry about the rings being torn by something on the trail, and you never have to worry about if the rings have been sufficiently lubricated so they do their job in the future.
But, I will grant you that if luck prevails, a ring chain will serve you fine. -And should be used if there is muck and slop involved.

Jaybird, what lube do you recommend? I use maxima witch is pretty gooe. You may be right I would just usually spray the lube until it is dripping. Maybe 30 seconds to get this effect. i never spent much time cleaning the chain. Maybe that is why the stock chain doesn't last long. I do have an x-ring that is vitually maintnance free. I use maxima chain wax now and two years no adjustments needed. I know there been threads on pro's and cons on both, but man they are like ten pages.

I guess when I say enduro I mean a hare scramble track down the road. I used it when I was just learning but now I am just a mx track guy. maybe that is the reason why I have no issues. I still just lube the chain one for a full day of riding.

I am always open to new ideas... :nod: Hope we didn't steal the thread :laugh:

Jaybird · May 24, 2005

I think this discussion is exactly fitting to the thread.

Many folks have great success with ring chains. Using them on the track, there is much less chance of anything catastrophic happening to the rings, like can happen on the trail.
But just one ring going bad, and allowing in contamination, can lead to an accelerated death of both chain and sprockets.

I recommend dry-film penetrating type lubricants for all chains. If I gave you a brand name, I'd be spamming so I won't go there. You'll figure it out.

If you want to read what I have published on this issue, you can go to:
http://www.best-motorcycle-chain-lube.com/chain_maintenance.htm#chain-maintenance-top

Camstyn · May 26, 2005

Jaybird, what are your thoughts on Maxima Chain Wax? I've been using it for the past few years and has left me with a good impression.

2003 KX250 chain keeps getting loose

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