[BLUETARD]

Picked up an 09 450x back in October. Super impressed with the bike so far, absolute blast to ride. But I'm a bit concerned with a noise that sounds like its coming from the top end. I know that the newer 4 strokes have a short skirt on the piston and am not sure if this is a normal sound for motors like these. Under idle or with no strain on the motor just revving it there is never a sound. But it comes and goes wile riding. It's most likely to happen if I'm at a low rpm and roll onto the gas. Not every time. But seems to be more now than it used to. Stars easy, runs fine, just a weird noise I haven't had in previous toys much if ever. Sounds like piston slap or something. Should I be worried? If it's an issue, what should I be looking for? Doesn't seem like its in the valve train.

[JimDirt]

Are you positive you are not hearing Chain Slap ?? , when the drive chain is too loose it will slap against the swing arm and you will hear rattling pretty much how your describing it

[BLUETARD]

I suppose that could be possible. I'll double check the tension and ajust if needed. I really hope it's something that simple that I mindlessly missed. I'll probably be able to get back out today and see if that fixes it.

[Back2-2]

With the bike is on a stand in neutral and you go through the RPM's that you were hearing the noise and you do not hear it then it is probably chain slap. Otherwise it could be sounds being transferred and reverberated up through from the skid plate.
If you have an after market aluminum skid / bash plate those make transfer all kinds of noises that can drive you crazy. I always add full layer of rubber on the inside of the plate to help. When you first ride these 450X's that is one of the first things you notice - it sounds like they are about to grenade into pieces. The rubber liner helps but some of it just takes a getting used to. My first plate was a Flatlander brand and it did not transfer near the noise my much heavier better constructed and better protection Works Connection plate I have know does.

Chain slap & skid plates are the ok noise makers on these bikes - It's hard to pin point when riding.

One additional note - Chain slap is usually heard when the bike is lugged down and chugging and also in heavy braking choppy or rough points of the track or trail where you are quick off the gas and braking pretty hard. The chain is bouncing and hitting the plastic swing arm protector. You get some of that even with a correctly set chain.

[BLUETARD]

Yah I'm realizing now that it may very well be good old chain slap. Everything that back said is spot on. I a just edit that chain a bit tighter (seemed pretty good but figured a tad tighter wouldnt kill it) and it lessened it a bit. Rode a little without the helmet and it adds up a bit now that I have a clue. Just never had it near this much on any other bike. Had me worried. Thanks guys. Now I feel a bit dumb for not putting this together on my own.

[JimDirt]

No problem , glad to help , and there is never a dumb question around here !! , and how do you think most of us , figured this out , it was by asking what we thought were dumb questions

[Back2-2]

I do not have the manual in front of me [I'm sure Jim will correct me if I'm wrong] but I believe the proper chain adjustment is approx. 1 1/2" delta swing up & down about mid way on the swingarm -Bike on a stand.

Do sweat the questions - That one gets asked frequently by new the CRF's riders.

Great bikes but they are a little noisy.

Don't forget about rubber on the skid plate to help quite the beast down. I do the entire inside helps immensely. Some just do where the plate touches the frame.

Good luck & have fun.

[JimDirt]

I just do the "3 finger" measurement , basically 3 fingers like if you were pointing at someone , but with the index,middle and ring finger together , and place it just behind the chain slider , and the chain should be snug on your fingers but you should not be able to spread your fingers (like a peace sign) ,and it should not compress your fingers so they overlap , its not "exact science" accurate , but its close enough to keep the chain where its supposed to be , and it minimizes the noise , the rest of the chain noise i just don't pay attention to

The Service Manual Measurement is 1.0 -1.4 inches , so 1" to 1-1/4" slack measured where i stated just behind the slider on the swingarm itself, while the bike is resting on a bike stand (not the kickstand)

[Back2-2]

Told ya he would have to correct me

Use the described technique in the owners manual. Engineers figure this kind of stuff or so you don't have to. 1" to 1/2" to avoid slap.

[JimDirt]

lol , no disrespect meant , Back2-2 , and for Engineering purposes , my "3 finger" method gives me 2 1/4" slack measurement , so a bit on the loose side from manual spec , but again , its just what i do on "my" bikes (the swingarm i had to replace on my R was from me not changing the chain slider before it wore thru on the bottom of the swingarm pivot bearing area after 6 years of use ,(slacking on my chain slider maintenance for lack of a better description) not from my meticulous chain tension methodology)