kdx 200 SR chain rattle

[Yamablue]

The sypmtoms are: At lower to mid RPM's when under power, the drive chain vibrates back and forth. It must move a whole chain width to one side, then the other at times.

The sprockets are both lined up and in good shape, as far as I can tell. When I look down the chain from the rear tire, it looks totaly straight, and it's an O Ring chain I am using.

I notice on the plastic chain guide/guard there is 2 tracks where the chain has been sliding on. The current one that it runs in is deeper than the original. But overall it looks in fair condition.

Possible remedies??
-improper chain slack
-plastic chain guide(on swing arm) worn
-just plain resonation from the engine etc?

Any thoughts would be appreciated, because I there shouldn't be any vibrations in the drive train.
Thanks!

 

[Jaybird]

Check to see if you have proper adjustment on the chain.
See if the rings look like they are in good shape. How long has this chain been run?
All chains will wear eventually and will get sloppy. A ring chain that is missing rings or stretched badly may shake quite a bit with some vibration working on it.
If well adjusted and chain in good shape, maybe you just have a vibration at certain rpm problem. It happens.

 

[Yamablue]

I know my sprocket set up is all good. Nothing is worn out etc.
The chain is in great condition and isn't stretched.
I guess I will live with it.
Thanks anyay

 

[jaguar]

Hold your finger tip onto the side of the rear sprocket while the rear wheel is suspended in the air and rotate the tire and see if the rear sprocket wobbles. Could be that you hit it onto a rock.
Sighting the chain and/or depending on the snail chain adjusters isn't good enough. You need to measure the distance from the swingarm pivot to the center of the rear axle to double check that the snail adjusters aren't lying. That distance on both sides should be equal.

 

[Jaybird]

Not to say you arn't in good shape, but if you are using the "eyeball" method to check alignment of your sprockets (and with the chain on, no less), how do you know you are set-up correctly?
How do you know that your chain isn't stretched? What did it measure out to?Do you have steel sprockets on both front and back?

I agree with Jaguar 100% about alignment. You also want to make certain that your sprockets line up correctly with a straight edge runing it from one sprocket side to the other after you have measured properly as Jaguar described. It's possible you are straight with the plane of travel yet the sprockets may be in a different plane...I'm not sure if that bike uses a spacer on the CS or not. (shrug)

I'm not trying to say you are lacking in your procedure, but many many folks will say they are spot-on, yet have no clue if they really are or aren't. More times than not, they have missed at least one critical point. Stuff "looking good" doesn't cut it.

Also....you stated that you know your set-up is good...how much chain slack did you set up on your chain? What procedure did you use to accomplish this?

You asked if maybe you had too much slack, yet you now know your set-up is good...???...

 

[kdx633]

dont forget about swing arm bearings

 

[Yamablue]

I run steel sprockets front and back. The O Ring chain is not stretched. I can barelly lift it off the rear sprocket.

I'm sorry if I sounded 100% sure on all the specs and settings. The truth is, this, with bike originating from Japan, and being a SR model, I don't have a owners manual or clymer book. I just picked up the bike ready for the road!

Though, I have owned previous bikes that I have used the "eyeball" method and haven't had a single problem.

I appreciate the concern, and will take into consideration all points said. Before I take any action, I will measure the distance on both sides of the swingarm (rear bolt to swing arm bolt).

Again, thanks all!

 

[Yamablue]

Jaguar, for some reason I can't PM you. Not to sure what's up with that.

Any way, why did you chose PC for a pipe? Why not a FMF fatty?
Who did the exhaust port work?
I have looked at your link for the SR mods. The 35mm carb looks good, but what about my oil injection?

Lastly, where did you purchase your bike from? Where they ever sold in the states? Mine was sold in Japan, and shipped over ('87 model)

I'd appreciate any info..
Thank you,
Spencer

 

[jaguar]

At the time I was doing high speed fire-road riding and wanted more hi rpm power which the PC pipe was known to give. And now that I'm doing motocross it is still a good choice for me.
I had to have it resleeved (the cylinder) and the shop uses virgin sleeves without ports and so the customer can tell them to do anything special with the ports. I wanted more low end so I told them to cut out the exhaust port to be lower at the top edges. Next I grinded off a little off the transfer ports tops and that brought the powerband up higher a bit but how it is now is really sweet since its powerful (I got one holeshot the last race) but linear in its power delivery (whithout any power surges at any part of the powerband which also makes it easy to ride on the street).
But I still need that 35mm carb to give me more top end power which is still somewhat lacking. But in your case you'd have to stop using the oil injector since the carb boot for the 35mm carb doesn't have that inlet for the delivery nozzle.
Mine was a jap bike imported here.
What are you using your bike for?

 

[Yamablue]

Right now I'm using my bike for school transportation and some serious off-road riding (at least where I live!)

My bike's powercurve is pretty good on the bottom, keeps pulling until top rpm, where the pipe really hits. Pulls real good! I wonder what a 35mm would do?

If I was to order a pipe from fmf, or PC, would I order for a '87 KDX 200 SR? or a '93 KDX 200 R? I would have to use retainer springs, instead of the nut and bolt system right?

My bike being a '87, looks exactly like a '93 in Noth America.

Was the porting worth the money???

Thanks!
Spencer

 

[jaguar]

You can't order for a SR, only the R.

yes I'm glad I took the time to fiddle with the engine. I learned a lot and made the engine a lot better also.