Chain Slap (Revisited)

I'm starting a new thread about the infamous KLX450R chain slap noise, after the TT moderators recently deleted a couple of other useful threads on the subject...

I originally posted about this issue, after installing a new TM Designworks chain slider, only to have the chain slap become much louder on my bike. After reading a bunch of old posts from a forum search, and from some more recent discussions with the wise folks here on this forum, there's a few things I've learned...

The bike tends to have an inherent issue, where by a resonance occurs in the drive chain at certain speeds and under certain types of loads, which causes the chain to oscillate both vertically and laterally, more than many other models (CRF450 excepted).

I've found wear marks on my bike, where the subframe bolts to the mainfarme on the drive chain side, proving the chain is oscillating wildly through the lateral plane from time to time. But I've also noticed a distinct reduction in the chain slap noise, after following the suggestions of some other forum members to slip some innertube rubber under the chain slider, along with some RTV silicone. This suggests the chain is also oscillating wildly through the vertical plane. Also running the chain a little tighter than it should be, has worked to reduce the resonance and chain slap noise for some other forum members.

I'd like to encourage other forum users to share their ideas and suggestions in this thread, about fixes they have come up with to stop the chain slap, and the wild chain oscillations which cause it.

Please don't offer to sell any homemade solutions you may have come up with, so the mods won't delete yet another useful thread on the subject.

Thanks in advance.

:smirk:

I found keeping the chain on the tight side of the manual recommendation reduced the noise. Almost no noise at all when tight but as soon as the chain stretches slap comes back.

Don't know who said this but i quote "When you think its too tight its just right"

My bike still has the OEM sliders front and rear and as DRZ400SK4 said with a replacement T.M designworks kit he found it to be louder which i have no experience on so i don't know bout that one but as i am now worn though my OEM rear slider its time for replacement i am going to try a Acerbis replacement insert and will post as soon as i get it and fit it on any difference.

Also i saw one of the other post that now have been deleted was an extra guide screwed to swing arm up near the sub frame (if your reading this and it was you can you repost please) It was an awesome idea but i am hesitant to drill into my swing arm.

So this got me thinking of an idea similar but with out the drilling.

Replace the left hand side subframe bolt with a longer one that goes though and bolts a small urathane or similar material block on the chain side (say 2x2inch square and maybe a little smaller than 1/2 inch thick and a tapered side on the rear side to guide the chain without grabbing the block)

I have not try this yet as i have not got the tools to do so but any building supplie shop should have cheap items needed.

I dont think this will stop the slap but will reduce the lateral noise and the wear on the sub frame that occurs when loose

Religiously maintain your chain between rides. I use digital calipers, measure 2" from the bottom of the stock chain slide to the middle of the pin on the chain in multiple spots. I do this with the chain pulled up firmly and the bike on a stand.

I clean and oil the chain after every ride, and very carefully adjust the slack, using calipers. It really doesn't take much time to do.

3000KM on the stock chain and sprockets, all offroad and still in spec. The only reason I replaced them was because I had the swing arm off.

Chain clatter has never been an issue.

Religiously maintain your chain between rides. I use digital calipers, measure 2" from the bottom of the stock chain slide to the middle of the pin on the chain in multiple spots. I do this with the chain pulled up firmly and the bike on a stand.

I clean and oil the chain after every ride, and very carefully adjust the slack, using calipers. It really doesn't take much time to do.

3000KM on the stock chain and sprockets, all offroad and still in spec. The only reason I replaced them was because I had the swing arm off.

Chain clatter has never been an issue.

Ditto i do the exactly the same 3100km on the stocker didnt wear all the way through on mine had about 8mm to go at the front of the slider but a small bit about 1cm peice ripped off and now the chain hits the metal bracket

I maintain tension and lube my chain religiously, and I'm very careful to align the axle by measuring, as opposed to usuig the marks on the adjuster blocks. With the stock slider, chain slap was minimal, but with the TM Designworks slider it was much louder, to the point of being really annoying. I could hear it plainly, even over the rumble of my full FMF exhaust system.

A sliver of innertube rubber and RTV silicone has reverted the noise level back to about the same as it was with the stock slider now, however.

Replace the left hand side subframe bolt with a longer one that goes though and bolts a small urathane or similar material block on the chain side (say 2x2inch square and maybe a little smaller than 1/2 inch thick and a tapered side on the rear side to guide the chain without grabbing the block)

I have not try this yet as i have not got the tools to do so but any building supplie shop should have cheap items needed.

I dont think this will stop the slap but will reduce the lateral noise and the wear on the sub frame that occurs when loose

When I saw the wear marks on the frame behind the subframe bolt, I was thinking the very same thing.

:smirk:

Edited by DRZ400SK4

Not only do I have all that wear on the frame, half the knobs on the side of my tire are gone.

I did, however, agree to try the "bootleg" guide, which is less about a guide and more about stopping the side-to-side slap. I have the TM Guide, as well.

Soon as I get a chance to ride the damn bike, I'll post any experiences.

Replace the left hand side subframe bolt with a longer one that goes though and bolts a small urathane or similar material block on the chain side (say 2x2inch square and maybe a little smaller than 1/2 inch thick and a tapered side on the rear side to guide the chain without grabbing the block)

I thought about this before designing my "bootleg" glider. It should work very well provided you can keep the small block of urethane on the threads of the bolt....and provided you could find a bolt of the same type that is long enough to engage the urethane sufficiently. The subframe bolt on the right side is slightly longer, but not quite long enough....:smirk:

Keep in mind that if that piece of urethane comes off when you are riding, the chain will quickly destroy the bolt and it would be very difficult to unscrew without damaging the frame.

The main reason I did not go with this idea...even though I thought about it (and even made a prototype)...is the placement of the glider (combo guide and slider); in order to be most efficient, it has to be near the middle of the chain run. The spot you are talking about is only a few inches from the countershaft sprocket. My goal was to stop the slap entirely, not just protect the frame.

Still, it would prevent chair wear on the frame, even if it didn't stop the noise. I say try it and post pictures and results here.

Always looking for a better way.

G31m...

I really like your solution. I just wish there was some way to clamp the bootleg glider to the swingarm, instead of drilling and through-bolting it on there.

May I trouble you to post a photo of it again, in this thread?

Anyone thought of using a roller instead of a block of rubber kinda like a roller guide that spins horizontally with the chain. Im just thinking it wont wear out as fast. kinda like one of these in the pic twobrothersreplacementg.jpg

Uploaded with ImageShack.us

The marks on the swingarm adjusters cannot be used to align the rear wheel accurately. If you use them, you will get a sideways chain oscillation . If it's off by as little as .25mm, you are waaaay off of alignment, and the chain is torquing.

Motion pro makes a chain/wheel alignment tool that will help correct the

problem.

http://www.rockymountainatvmc.com/docs/08-0048_Package%20Insert.pdf

The stock chain is junk, and will begin whipping around in 10 hours or so. Get a good X-ring chain (DID VRT2) and you will not have to mess with it for 100 hours or so.

Oh, and 'tight is right' for chain adjustment is WRONG.

You just stretch the chain faster, and you run the risk of damaging the counter shaft seal, and bearing, and doing possible transmission damage.

The ONLY way to find the proper chain adjustment is to load the bike with enough weight to put the the swingarm in it's level position with the CS sprocket, adjust the chain less than tight. Then, with the bike on a stand, find a piece of wood, or something similar, to use as a 'distance wedge' under the chain on top of the swingarm, so you can check for proper tension easily.

The marks on the swingarm adjusters cannot be used to align the rear wheel accurately. If you use them, you will get a sideways chain oscillation . If it's off by as little as .25mm, you are waaaay off of alignment, and the chain is torquing.

Motion pro makes a chain/wheel alignment tool that will help correct the

problem.

http://www.rockymountainatvmc.com/docs/08-0048_Package%20Insert.pdf

The stock chain is junk, and will begin whipping around in 10 hours or so. Get a good X-ring chain (DID VRT2) and you will not have to mess with it for 100 hours or so.

Oh, and 'tight is right' for chain adjustment is WRONG.

You just stretch the chain faster, and you run the risk of damaging the counter shaft seal, and bearing, and doing possible transmission damage.

The ONLY way to find the proper chain adjustment is to load the bike with enough weight to put the the swingarm in it's level position with the CS sprocket, adjust the chain less than tight. Then, with the bike on a stand, find a piece of wood, or something similar, to use as a 'distance wedge' under the chain on top of the swingarm, so you can check for proper tension easily.

So this will stop the slap?

So we know the punched chain adjustment notches can't be trusted for accurate alignment, but what about using the lengths of the exposed portion of the adjusment bolts on either side? Can accurately measuring these be used as a reliable way to check alignment?

So we know the punched chain adjustment notches can't be trusted for accurate alignment, but what about using the lengths of the exposed portion of the adjusment bolts on either side? Can accurately measuring these be used as a reliable way to check alignment?

The only alignments that matter are wheel to wheel, and wheel to frame. Since dirtbikes don't have precision alignment spots on the suspension or frame, we don't get the luxury that street bikes do. We have to improvise, and measure with a tape measure. Pain in the butt. If you assume the frame is true, the steering head is true, and the swingarm pivot and arm are true, using chain torque as a way to determine wheel alignment to the above areas, we get a quick and easy way to get the rear wheel and chain angle straight, at the same time.

If you use a precision wheel alignment tool, and then try the chain torque method, you will find that they are very close. Close enough for most people.

WheelAlignmentTool.jpg

Motion-Pro-Chain-Alignment-Tool-2010-MD.gif

Now you may think this is 'anal' and way too detailed for a dirtbike; but consider this:

- the hash marks on axle blocks are about 3mm apart (varies)

- at 'eyeball accuracy' you might get .5mm accuracy if you are very careful

- .0125mm of error on the axle block is equivalent to 1-2 degrees of error at

the rear wheel.

- 2 degree of frame mis-alignment is considered a 'salvage' specification for

an insurance company repairing a damage motorcycle.

Using the Motion pro adjuster is fast and easy and cheap.

DSCN7990.jpg

Anyone thought of using a roller instead of a block of rubber kinda like a roller guide that spins horizontally with the chain. Im just thinking it wont wear out as fast. kinda like one of these in the pic twobrothersreplacementg.jpg

Uploaded with ImageShack.us

That was the first thing I thought of, yz. But, when you move the swingarm through its full compression travel, you'll see that there is insufficient room between the chain and the subframe brace for a roller. There is barely enough room for the 1/2" thick Delrin shown in urnuts' photo.

Believe me, I've explored every possibility I could think of in coming up with the bootleg glider....I'm a bit anal that way.

So we know the punched chain adjustment notches can't be trusted for accurate alignment, but what about using the lengths of the exposed portion of the adjusment bolts on either side? Can accurately measuring these be used as a reliable way to check alignment?

Manufacturing tolerance being what they are, you might find this is an accurate way of measuring rear wheel alignment on your bike, but on my bike it might be unacceptable.

Best way is to measure the distance between rear axle center and swingarm pivot center; should be the same on both sides.

Best way is to measure the distance between rear axle center and swingarm pivot center; should be the same on both sides.

Got it.

That'll be my method from now on, too.

Thanks.

:smirk:

Best way is to measure the distance between rear axle center and swingarm pivot center; should be the same on both sides.

X2

Using the MP tool makes this task quick and easy!

Yes but will this tool stop the slap?

And also in my original post i didnt say run the chain over tight i said run it at the tight end of the manual specs 52-58mm (2.0-2.3inch) Yes i did post if you think its to tight its just right i was refering to the manual spec. Sorry for the poor explanation.

I run mine right on 52mm and almost no slap at all but when you get a little stretch it comes back.

I am at 64 hours now with little wear to the sprockets as for the chain looks fine but you cant really tell till she snaps i spose b/c it looks fine no visiual wear but i havnt taken it off to see how much it has stretched.

As for the alignment tools they look like a great way to get it spot on.

I just want to know if this will have much of an affect on the noise reduction?

Yes but will this tool stop the slap?

And also in my original post i didnt say run the chain over tight i said run it at the tight end of the manual specs 52-58mm (2.0-2.3inch) Yes i did post if you think its to tight its just right i was refering to the manual spec. Sorry for the poor explanation.

I run mine right on 52mm and almost no slap at all but when you get a little stretch it comes back.

I am at 64 hours now with little wear to the sprockets as for the chain looks fine but you cant really tell till she snaps i spose b/c it looks fine no visiual wear but i havnt taken it off to see how much it has stretched.

As for the alignment tools they look like a great way to get it spot on.

I just want to know if this will have much of an affect on the noise reduction?

It depends on the condition of your chain, your wheel alignment, your rubstrip attachment (rubber or glue insulation), and how quiet your exhaust is !

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