CRF 450R question (knocking sound)

[Fox250R]

I've had thisCRF450 for a while now and its making a very loud knocking sound at low rpms..I did a leak down on it and got up to 60psi with a 5 psi leak and you could hear sounds like a peculator bubbling..Then i did a comp test and it was showing me 30psi..It starts and runs just fine so this makes no sense to me...Im guessing its my piston or rings or both.. the link im going to post is my bike and the sound its making.. When i posted the film i thought i had fixed it and didn't start it for like a year..then just a few days ago i pulled it out and fired it up and its right back to square one.. I just wanna sell this pos but i cant sell it making this sound... The guy who owned it before me said he rebuilt the top and bottom end right before i bought it and the bike never really dropped rpms enough for me to notice the sound..If i would of heard this i would of told the dude to stick this 450 up his azz lol...


Honda wants to charge me like 300 just to tear it all down and look to see what it is.. I just dont trust my 4stroke skills enough to tear it down myself..I just wanna know what it is so i can get the right parts for it.. Many ppl on youtube seem to think its the valves or timing chain.. I had both of those looked at 3 or 4 times now..I've spent over a grand now just trying to figure out what this sound really is.. anybody out here have any idea? Im just at a loss! Im about to sell it for 400 bucks.. Thanks


http://www.youtube.com/watch?v=Gtie98Go8Wc


I've really never seen anything like this before..30psi and it pulls wheelies in 4th with no prob LOL

[canucksfatcat]

Sound like your connecting rod bearing in the lower end is done. If it gets worse it could take the whole bottem end with it.

Good luck with that,
P

[Jason Hall]

Yes I agree, It needs a crank. I will be Installing a new crank In mine this winter because It's noisy. Mine rattle's a little when just putting around, when you first throttle Into It. I have noticed the aluminum frame echo's the sound alot more also.

[Fox250R]

Has new hotrod crank and all barings are new...We did this thinking it would fix the knocking but it didn't...We rebuild the topend adjusted the valves and timing as well lol....I have no idea what to do now...What else can be causing this? Now im into it just in the motor around a $1500.. I mean comeon give me a break! NO ONE KNOWS LOL

[Jason Hall]

How about the counter balancer bearing's? I change mine, and It did help slightly. I'm starting to think maybe because of the short piston skirt that maybe our cylinders are just worn to much to use a stock bore piston?

[Fox250R]

im using a stock bore flattop wisco.. with like myabe an hour on it....But the sound is coming from the top of the engine so its something up there not the crank..HELL I DONT KNOW ANYMORE LOL.. I even took it to someone who works for curtis sparks racing and he said the 02 crf450s knock lilke that LOL....WTF?

[z400guy28]

I not sure either but to me sounds like your piston is slapping against the cylinder wall or the head. It doesn't sound like a bad crank. My Banshee's crank went on me and it didn't sound nothing like that. But then again the Shee was a 2 stroke and i don't know if the would make the same noise. What ever it is good luck solving the problem.

[Fox250R]

I not sure either but to me sounds like your piston is slapping against the cylinder wall or the head. It doesn't sound like a bad crank. My Banshee's crank went on me and it didn't sound nothing like that. But then again the Shee was a 2 stroke and i don't know if the would make the same noise. What ever it is good luck solving the problem.

humm i dont know either lol...We basically had the motor rebuilt from top to bottom and its still knocking lol..I mean crank, rod, bearings,gears, timing gears and chains,valves piston,rings gaskets........I did notice my coolant is Low and i just filled it..So maybe a gasket somewhere is wasted...comp is around 30-40 psi but it runs awesome...It pulls away from my R around 4th gear....starts 3rd or 4th kick cold everytime.. Ive never seen anything like this..

[300rman]

well, if the comp was 30 or 40, it wouldnt run. PERIOD.

if the whole thing was completely rebuilt, and you trust the work done, run it some and see if it gets louder. i cant see it grenading if the crank and bearings are new.

[cody2]

Ill give you $500 and take it off your hands! Yeah its a tricky call, i think honestly i woudlnt go with the $400 to tear it down, a lot of times the dealers just dont know what there doing, i had a dynatek programmable ignition they took it off and charged me for a stalk one because my bike woudlnt start. It had warranty on it and they kept it, i had to go back up to the dealer freak out for an hour and they gave it to me but charged me for the work and the other one which is in my garage never to be used.

[G-MAN RACING]

im a 4 stroke guy. and it sounds to me that the timing chain is slapping the side of the engine. are your chain guides there. they keep the timing chain in place so they dont have play. believe or not that has happened to people *Edited**Edited*.

[NEWDUCK]

Theres a few things it could be but the 30psi makes no sense to me. With 30 psi you would have to jump start your bike. But if it really is 30psi then either your valves are toast or your auto decomp really needs adjusted. The older crfs had problems with the timing chain slapping at an idle but you say they checked all that out? Also at an idle my bike has a little bit of piston slap but not enough to concern me. Also this might be a no durr fix but if its making the sound while riding your bike at slow rpms it could just be your chain slapping your swing arm. Hope this helped some. Or maybe im off in my own world again and that didnt make any sense at all

[Jason Hall]

He probly did the compession test with the throttle closed. I think that would be the explanation of the 30 psi. My 450 makes a slight knocking sound when you are just putting around, and first throttle Into it. I was going to replace the crank In mine because It's the origional. Now that this thread has come up, I think I will be replacing the cylinder and piston Instead. I know mine Is not the timing chain slapping, because the noise I'm getting Is not a clanging noise, but a knocking sound. I'm almost certain fox250r and I have the same noise. Piston slap Is what I have determined my noise Is after reading this thread. I will post up a pic of how short the skirt Is on these new 450's, I'm amazed they don't flip over In the bore LOL.

[MTS]

Get a stethoscope, or a long screw driver and try and determine which part of the top end in particular its coming from, witch side ect,,,

[motoman110]

Im not sure if yours could have this issue. But I just had a 450 like yours but it was practically brand new in my shop with the same type of deal. He had 3 experts at milvile tell him it was crank bearings. So I tore it all down for him. Crank was perfect! All the tolerances were in spec. Well I started to just rotate the engine by hand with it apart. Turns out this knock was coming from the gears for the balancer shaft! The guy installed a recluse clutch and in the process of putting the clutch cover back in he dropped one of the dowel pins into the clutch side. Well that found its way into the gears of the balancer shaft and mard them up enough to make a rather loud knock. Not sure if yours could have a problem like this but I figured I would share my story lol.