2024-09-23 Cam Chain Replacement

RBY's cam Chain repair thread.

 

KZQ wrote:

RBY's cam Chain repair thread.

I think KZQ is saying it would be great to start a new thread about your work, making it easier for future cam-peeners (pun intended, America is electing new prez in Nov). 

And Thanks for the pics!

 

Trying really hard not to over think this - would love to keep peening but terrified I'll over tighten my last good joining link. 

Take a small flat blade screwdriver, insert under your peened link, try to 'pry' the link apart. Carefully note any movement. If movement, if it wiggles, how much does it wiggle?

Go to a factory link and repeat, compare.

If identical, and I think they will be, you're done. Put the tool down and walk away!

I can't imagine there being much side stress on that side plate. And if something went south bad enough to create that kind of stress, well, your phooked anyway. 

 

For the record-
The pins of the master link are an interference fit in the side plate of the master link. (.003"-.004")

First thing is to install the master link on to the chain and then press the side plate onto the master link pins. You know when you have it just right when the chain is ever so slightly tight when you try to bend the chain at the master link. if it's too tight  flex the chain sideways to loosen it up until you're happy.

Now you're ready for peening. Set up the pieces of the tool and place over the pin to be peened and tighten down the peening head by 3 flats of the peening head and note the position of the handle of the peening head, then back off to inspect the end of the pin. You're looking for an impression just enough to see that the end of the pin is not flat anymore. Any visible impression indicates that you have yielded the end of the pin and displaced the metal. Any impression will be enough to ensure the pin can't come out because , remember that the pin is an interference fit to start with and now you have displaced more metal outboard of the side plate making the interference even greater.
if you don't see an impression in the end of the pin, install the tool again and tighten up the 1 more flat of the head of the peening end from the position you noted from the first squeeze. Back the tool off and check the end of the pin again looking for some kind of an impression. if you see an impression, you're done. If not repeat this step and again go one more flat of the peening head. It's that simple.
RBY's pic of his finished chain is great. Great job for a first attempt. The impressions look really good and the link is not binding. Patience is a virtue. The only tricky part of doing this job with the chain installed in the engine is dealing with all of the plates. There are 3 or 4 plates + the master link + the outboard side plate and until you have all the pieces together and the side plate pressed over the pins of the master link, there's a possibility of dropping a piece down into the engine. Stuffing the cavity with rags is paramount.

Great job RBY !! Be proud. You earned this one and thanks for posting.
KB

I didn't trust myself to break the old cam chain and install joining link in new one, over the engine - even with the sump off there was just too many places for those tiny link plates to hide if they slipped past the rags, or fell through when removing the rags. So I did everything in front of the engine. After threading the new cam chain through (on end of the old chain, after breaking both) I had both ends hanging down over the front of the engine. Then made up a simple platform with wooden blocks, a few centimeters below the top of the engine cases, so I could work on the ends with one hand while manipulating plates and pins with the other. Hopefully the photos will help explain (recreated using old chain and stuffed joining link). Hold both ends together with fingers of one hand, insert joining link through first couple of plates, then insert first of the three intermediate plates so that it is aligned but resting on the joining link pins. Hold that plate in place with a third finger, pressing down slightly, then gently ease back the joining link until the inserted plate pops down and giggle the joining pin through this to next couple of plates, repeat for second and third plates. As the final outer plate of the joining link is a press fit, it wont easily sit in place so I used a dab of assembly grease to hold it there. The platform was also handy for resting the riveting tool on so you didn't need a third hand. And I used small fine grinding wheel on the Dremel to take the heads off pins before pressing them out to break the chains - made it a lot easier. Hope all this helps the next person. Oh, and if you think your old cam chain is just on the service limit (length measured between 20 links) like mine was, it will be ok, check out how worn the pin is from my old cam chain! [attachment=12308]

I would have been nice to compare the old link plate to one of the new link plates. What I see in the pic is the bore in the link plate in the upper left is getting really thin to the edge of the link plate and I would be more worried about that thinning more so than the wear on the pin.

One also has to remember that when the cam chain reaches the service limit, the stretch in the cam chain will retard the camshaft timing by as much as 8 degrees retarded. Add that to the stretch in the primary chain and you end up with more camshaft  retarded timing, maybe as high as 13 degrees total retard. The adverse effect of retarded camshaft timing is that the intake valves will close late, reducing the amount of charge compression . It also upsets the timing of valve overlap to the position of the piston at top dead center resulting in less volumetric efficiency . All bad.

The effect the wearing of the primary chain has on valve timing is surely something that the designers of this engine must have thought about, surely, yet they went ahead with this flawed design. It would be interesting to check the valve timing on an engine that has covered about 20 thousand miles.   Are you intending to engineer some means of adjustability into your camshafts, Kawboy?

Yea, I got plans for an adjustable camshaft sprocket. Life just keeps getting in the way. If isn't one thing, it's another.the CRF450 camshaft sprocket is the only camshaft sprocket that will work. A minor mod will need to be done to slip it over the cam lobes and a backing plate will need to be machined to attach the sprocket to the camshaft after the original sprocket is machined off.Ape makes an adjustable sprocket for the CRF450 and also Falicon. I have both of these waiting for some time to play machinist.



 

 

This is a pic of a stock non adjustable CRF450 camshaft sprocket that one would remove to install either the APE or the Falicon sprocket. I came up with this idea 8 years ago and haven't found the time to work on it.