[Duncan]

Hi guys
Just new to the site and hoping for some help.
I've got a 06 crf450 runs grate have had it about 3 months
Last ride I heard a slight rattle or clatter coming from the engine
Under heavy load. Got home and went right over it couldn't find a thing
Next ride some noise but it's getting worse I've cheeked chain tension and for chain slap and it's all good it sounds like aluminium tapping aluminium and it might be coming from the engine it's hard to say.
Anyway any help would be great thanks

[hall_philip]

Does it make the noise while on the stand?

[Duncan]

No only under heavy load

[JimDirt]

I am thinking its your chain hitting the swingarm , check the chain tension and make sure its not slightly loose (i know you said you checked it , but if its off just enough it WILL hit the swingarm), it can sound like its coming from the engine , the only other sound that would rattle would be a worn timing chain and/or tensioner , if it were valves loose they would tick all the time , so if its under load only the only things it can be is a chain ...... you have 2 ..... timing ,and the drive chain , thats it

Take 3 fingers (index,middle and ring finger) hold them vertical (index finder top ,ring finger bottom) stick them under the chain just at the back of the slider, but on the swingarm itself , if you can spread your fingers , even slightly , the chain is too loose and it will slap the swingarm

Otherwise you need to check the tension on the timing chain ..... remove the tensioner , and stick your finger inside the hole till it hits the chain , if you can push the chain and it moves more than 1/16th of a inch max the chain is most likely stretched and needs replaced


Check (and adjust ) the rear chain first , if its just slightly looser than it should be it WILL rattle , ride it and see if that stops the noise , if it does not , then check the chain , if it moves then you know you have to replace it , it should be tight enough that you cant lift it off the cam sprocket with the tensioner out , if the chain comes off the sprocket with the tensioner removed , then that will also confirm the chain is stretched

[Back2-2]

Chain slap is on "off throttle" condition not under full load. If it is truly happening under as you stated "heavy load" then you have either cam chain issues or possibly swingarm and or suspension pivot point issues as in worn or loose points. With the bike on the stand try moving the swingarm in all directions feeling for the culprit. You may have to disconnect the rear shock to really check these things. Another item to check is the rear caliper that it has not become loose and rocking back and forth. Take a really good look at all those points. Don't overlook the steering head being loose.

Good luck & take your time inspecting.

[riddler9]

I would also check the rear sprocket bolts and engine mount bolts.

[Duncan]

Thanks guys
I've checked all suspension joints and they are all good no movement at all even disconnected the shock when I did itall fine.
I have just put new chain and sprockets on it and new rubber chain guide on the swing arm there are no marks on the swing arm anyware that I can find. I have adjusted chain tention as per manual and will double check with the 3 finger check tonight.
And will test ride after

[Back2-2]

Check the engine mount bolts and skid plate bolt points.

[JimDirt]

Question , do you have a ALUMINUM skid plate on the bike ??

If so , the engine noise can resonate and it will be loud and sound like the engine is coming apart , if this is the case , take some weather stripping or rubber strips and place them on the skid plate where it contacts the frame rails


And the chain can hit the swingarm under acceleration when the suspension is compressed where the swingarm is level (and the chain is most slack), it will hit the underside of the swingarm where the slack in the chain is ,if the chain is not adjusted correctly .....

This is why bikes have a chain guide near the rear sprocket at the bottom , because the chain can become so slack , it can come off the sprocket at the bottom when under acceleration load , so the guide keeps the chain aligned with the sprocket when it is the most slack , that is why its called a Chain Guide it guides the chain on the sprocket when there is slack in the chain , and if the chain is out of adjustment , that is when it will hit the swingarm

[Duncan]

Ok took the bike for a quick ride last night and it seams a lot better but not gone so I will try fine tune the chain tention thanks for all the help

Only other question would be is often if I back off throttle and then open it wide up it will stall or flood??
Bike I'd standard as far as I am aware apart from a yoshi exorst
Would this just be carb tune???

[JimDirt]

I would guess there might be a issue with the Accelerator Pump timing or the AP Diaphragm may be bad , that is usually what contributes to a throttle blip bog

First make sure your jetted for your elevation (there are other variables that could change these numbers , but this is a basic guideline that should work in most situations)

MAIN JET:
Sea level 165
2000 ft... 162
4000 ft... 160
6000 ft... 158
8000 ft... 155

PILOT:
45 should work about anywhere in those levels


Fuel Screw:
1 turn out or less your too rich and need to go down at least 1 main jet size , 3 turns or more out and your too lean and need to go up at least 1 jet size , you should be between 1 1/8 - 2 3/4 turns out

Also , VERY IMPORTANT ... Make sure (you have to have the subframe up and the airboot off the carb so you can see down the throat of the carb)that the Accelerator pump squirt just barely misses the slide (this is AP timing i was talking about) , if it hits the slide you will get the bog , also make sure when you give the throttle a twist that the stream is long , not just a quick squirt , it should give a nice long squirt and as i mentioned , just barely miss the slide

DISCLAIMER:
I am far from a jetting/carb expert , but that is where i would start

[Duncan]

Great il see if it helps on next ride
I've got a bolt that the socket slipped on and won't undo now 8mm radiator shroud to fuel tank any ideas

[JimDirt]

Is the head just rounded or is the bolt spinning ??

If the head is rounded then try small Vice Grips

If the bolt is spinning in the tank then this is the fix

http://www.crfsonly.com/forum/viewtopic.php?t=13284url

When re-installing shroud bolts , use Anti-Seize to keep them from sticking again