[JMark]

New to the group< thanks for the add.
My 04 CRF450 blew the bottom end. I found a good bottom end from an 02. Install was going great, 02 bottom bolted right into my frame, 04 head fit perfect. When i try to put the timing chain sprocket onto the cam it seems to be a half inch short. Is there a difference, or am I just bound up somewhere?

[JimDirt]

Welcome to the site !!

You do have the Timing Chain Tensioner removed correct ??

[JMark]

yes, tensioner is out of the engine

[JimDirt]

The chain should be the same from 02-08 , same exact part # and 112 links , so there has to be something you are not doing right , either the cam tower is not seated correctly , or you don't have the chain on the crank sprocket all the way , or it is hung up on the little tab at the bottom that keeps the chain from falling off the bottom sprocket

You should be able to remove the gear (with the tower in place) and put the gear on , it will be snug , but it should go right on ..... it is possible when you assembled the head to the cylinder that you did not fully seat one of the guides .... that would put enough tension on it to prevent the chain from going on ....... You could try putting the sprocket on the cam , then unbolting the tower , and tilting it down , and try putting the chain on , then tipping it back up into place .... ... but if the head if fully seated and the guides are correctly in place it should fit ....

[JMark]

Thanks for the reply. I went back out this morning and tinkered some and there is nothing obvious. Everything seems to fit fine except the cam chain over the camchain sprocket. Maybe the bottom end isn’t an ‘02?

[JimDirt]

02-08 "should" interchange for the most part , the one who could tell you for sure is Ken , the owner of the site , but he was in a accident recently , and is pretty banged up , so he has not been on here much because of that .... I would say to confirm with a Honda Dealer , but they won't really know , as they would just go by part # and if #'s are different for different years , they would not know what to tell you other than part #'s are different , but that does not mean they won't fit , it is usually just a updated thing , like compression ratio or something that could make a part # different , even though it would still directly fit ....

What you might try to do to confirm , is to call a engine builder like Pro Circuit or something , and ask what specific years top/bottom ends will directly swap as I have not tried mixing years too much , but I know cams(with towers) and heads and the crank will all interchange , flywheels are different , but only in weight , but will still bolt up ......................As the only thing I can come up with is that the chain is being held from relaxing all the way by something , which is why I asked about the tensioner , but 02-08 chain should fit any 02-08 engine configuration , so I would "assume" that any year swap would give the same result .... as I don't believe they changed cylinder height or anything like that thru those years , and I believe all the heads of those years swap out , and 02-04 are pretty much the same bike with the exception of internal suspension items and subframe (but they will still swap if you swap muffler system as well due to mounting difference , but I ran a 03 swingarm ,linkage and airbox along with a 05 carb on my 02 with no issues ......not sure what else it could be , that is why I thought tensioner or tensioner guides holding it from having that extra length you are seemingly missing ...

[Aussiecrf230]

The chain isn't partially off the bottom sprocket so there is not enough reach to top sprocket? Just a thought.

[JMark]

Sorry for the delay. I haven’t had time to go out and tinker with it.
This morning I had about 10 free minutes and I went out and held up on the chain while I turned the engine over. It almost got me there. I think if I had more time I could have gotten the sprocket into the shaft. Hopefully tonight. Thanks again for the help. I’ll let you know when I get it together

[JMark]

Cant figure how to post a picture of it, but my timing chain had a permanent kink in it. It took me a while today to figure it out. I had one from my old bottom end so I went thru that process and now the engine is back together. Thanks for the advice!

[JimDirt]

To post a picture you need a hosting site like IMGUR , you upload to it , then copy the link for Message Boards and paste the link in your post and the pic will show up

Well that would make sense ..... Looks like its new chain time ....... I am glad you figured it out .... its amazing how 1 little thing can screw things up so bad .....

[Aussiecrf230]

Probably best to get a new chain rather than use one from old engine.