CRF's Only Forums

Hello all. New to the forum. Thank you in advance for any advice or help. Long story short, I bought a used 450R last year and decided to rebuild the motor from bottom up after experiencing compression issues (compression test revealed worn rings likely) once home and riding. Full disclosure, I'm no mechanic but I can follow a manual and relevant videos when needed and I had the time. New parts included main and auxillery bearings, cylinder, piston, wrist pin, rings, cam chain, tensioner, cam chain guides, valves, keepers, and gaskets. But now the problem, after the bike fired immediately and unlike before the rebuild, I can hear a knocking noise that I've somewhat narrowed down to the cylinder by listening with a long screw driver. What I don't know is if I have an issue (besides the knocking of course). Do new parts need time to mesh and wear in? I did not replace the cylinder head or valve guides although using prussian blue and a small bore gauge did not reveal any obvious out of spec issues. I attempted to post a video of the bike running, but I guess being new to the forum doesn't allow me to attach a vid. The bike only has a half-hour of run soft run time since the starting yesterday. Thank you again for your advice or input.

HeadDoc

Welcome to the site !!

What Timing Chain Tensioner did you use ?? , OEM , or Manual aftermarket ??? , wondering if the noise is a mis-adjusted Tensioner ........ Also , since you mentioned you are not a "mechanic" could it be possible you put the piston in facing backwards ?? (it has been done) , which would first off make the valves hit the piston definitely making noise , and could also result in a piston knocking noise from it not being positioned correctly .......

When you replaced the Tensioner and Timing Chain , did you check/inspect the Timing Chain Guides ?? , if they were excessively worn and you replaced the chain , they may be causing a slapping from the chain , and/or over extension of the Tensioner .....

How about the Oil Pump ,have you pulled the valve cover to make sure you are getting oil to the top end ???

These would be the first things I would eliminate ..... as they seem the most likely suspects .....

Thank you for getting back to me JimDirt. I used all OEM parts. I also replaced one of the cam chain guides (opposite the cam tensioner side) as it was excessively worn but did not replace the other. I have not pulled the head cover yet but I definitely will now that you mention it. As for putting the piston in backwards, I suppose its possible but when I put it in I remember taking my time and double checking because I was actually worried about that exact scenario but again I suppose I could have. I'm definitely concerned about my ring placement positions but I followed the ring orientation recommendations. I did not replace the crankshaft or piston rod assembly, but there was minimal lateral movement and no noticeable vertical play.

Are you sure that you are hearing the "normal" engine sounds. They are a little noisy which takes some getting use to over other brands. It sounds like you did a very diligent rebuild. They are quite straight forward to rebuild and actually pretty easy. If you used all OEM parts and used a manual you are probably all good. It's sometimes easy to be a little paranoid and think you hear something abnormal when it is actual a normal sound.
Just throwing that out there for you to consider.

Thank you Back 2-2. I had considered that and I do feel a bit paranoid. I wish I could post the video of the bike running for others to possibly hear what I think I'm hearing. I contacted my local dealer today and asked if their service techs would be willing to take a listen and they kindly agreed. Bad thing is they are booked out until mid July before they would be willing to work on it if there is a problem. Yes...I'm simply hoping for paranoid!

Like I said - these bikes are pretty rattly. If you have a skid / sump late especially an alloy one it greatly aggravates the sounds. I have a super heavy duty plate and had to install a rubber liner to it just so I could take the noise. I am used to very quiet tight engines and these CRF's take some getting use to.

Good luck and I hope it's nothing but just basic mechanical sounds. Let us know what you find or decide.

Thank you for getting back to me JimDirt. I used all OEM parts. I also replaced one of the cam chain guides (opposite the cam tensioner side) as it was excessively worn but did not replace the other. I have not pulled the head cover yet but I definitely will now that you mention it. As for putting the piston in backwards, I suppose its possible but when I put it in I remember taking my time and double checking because I was actually worried about that exact scenario but again I suppose I could have. I'm definitely concerned about my ring placement positions but I followed the ring orientation recommendations. I did not replace the crankshaft or piston rod assembly, but there was minimal lateral movement and no noticeable vertical play.

As for the piston , the valve reliefs would indicate front/back , if you put the larger reliefs facing the rear , you should be fine ..... if the ring gap as not where they needed to be (basically if they were all in the same position as far as gap goes) you would notice oil burning , or low compression , not so much a noise ..... it is also possible to put the rings upside down , but if you followed the procedure you would have noted the markings and should be ok as well

As far as the rod goes , if it was not knocking before you took it apart , it should not be knocking now , though a new piston does put a extra load on the rod/crank , unless something hit the piston , like a valve before rebuild , there should not be a issue with that .... It might be as mentioned and just be "normal" engine noises ..... though you did mention that it did not sound like this prior to the rebuild .... so that goes back to something you might have overlooked , or inadvertently done , but the only way to find out , aside from tearing it all apart again and double checking everything you did , is to either visually or physically , eliminate the obvious items , such as verifying oil getting to the top , while the valve cover is off , you can visually check the chain tension , to make sure the other chain guide is not the issue (if I replace them , I always replace both) .......

Video's help , but not always , as the noise is not the same on video as it is in person .... so a video may or may not help .....

But you should be able to embed a video into your post , as long as the video is on Youtube or Vimeo or some site like that , then you can embed it , or link to it ...

My understanding was that the engine was rebuilt "from the bottom up" so I eliminated my first thought of rod knock.
Chain slap usually from all that I have experienced sounds like exactly that - chain saw rubbing sounds. Not knocking.
I have also seen people put rings on upside down and run the life of the rings never knowing anything was wrong. I agree with Mr. Jim that if the ring gaps where not correct all that happens is oil getting past and being burned. No sounds come from rings positioning.
I think as Mr. Jim suggested - take a look under the valve cover and see that you are getting oil flow.
Maybe try a crank over / roll over [ not firing up ] to see oil flow and functions.

Thank you both so much. I will pull the cover and turn the engine over by hand. Hopefully I'll see oil flow and rule that out. If I can I will post a video. I will let you know what I find. Again thank you.