Topic: 650 cam in a 550 head.......Why WON'T cam chain fit over sprocket!!!

[Ryan 550k]

Hi folks.  So here is the issue.  I've been doing a slight rebuild on my 78 CB550k.  put new rings on, new gaskets, etc.  Wanted to put in a 650 cam, purchased one from an 82 650 Nighthawk.....was told by some other members it would work fine and as it turns out the only difference in the 650 cam is the lobe length.  ANYWAY, when I took my 550 cam out, taking the cam chain off was no big deal.  Getting it back on has been a HUGE struggle and I can't figure out why.  I didn't replace the cam chain, in fact the only thing that's new are the gaskets and the cam chain tensioner and guide.  I'm using the 550 sprocket of course and yet for some reason, after tightening up the tensioner to allow the chain the room it needs, there's still not enough slack to get it over the sprocket!  It's almost there, but lacking by about maybe 2 or 3 centimeters.  I just don't understand why I can't get it over the sprocket if nothing of major significance has changed.  It's like the chain shrunk.

I'm at a deadlock and need the help.  Thank you in advance.

[kenolds]

Did you bolt the sprocket to the cam already?  The chain has be meshed with the sprocket before the sprocket is bolted to the cam.

[Ryan 550k]

We tried it with sprocket bolted to cam, not bolted to cam, just the sprocket by itself and then attempted to slide cam in......none worked.

[lordmoonpie]

What you'd normally do, as long as the chain is long enough is...
Back off the camchain tensioner
place sprocket in the head next to camchain - I usually put both over my finger and the thread the cam in so sprocket and chain are loose over near but not on the cam center. Lower the cam into its position on retainers and position so the cam end marks are level with the head surface. Place the camchain on the cam sprocket and then and only then, lift the cam sprocket onto the cam shoulder. Bolt it all up....

If the chain is too tight to do this it implies your chain is too short and that in turn might mean you can't run the 650 cam. Before lengthening the chain or buying a new one, I'd check the cam cover will bolt down over the 650 cam. If you have clearnance to do that it might be worth having that longer chain.

[mlinder]

It's the 550 gear on the 650 cam, lordmoonpie.

[OldSchool_IsCool]

There is a writeup in the FAQ on this complete with pics.  Basically, align the crank to T1.4, slip cam under chain from right, slide sprocket onto shaft.  Set cam into barings, and align right notch with head mating surface.  Rotate sprocket so that one of the "mickey mouse ears" allows the sprocket to settle to a low point.  Slip the chain over the sprocket.  Fix the sprocket to the shaft with one bolt.  Rotate crank 360 to expose 2nd bolt.

I know this works with a 550 cam shaft.

[Ryan 550k]

I had not even thought about checking the FAQ section.  Lesson learned there.  Thanks OLDSCHOOL.
Well, I guess I'll give it a try this Sat and see what happens.

[Ryan 550k]

Working on a motorcycle engine is a practice that constantly humbles me.  There seems to be only one way to put in the cam and I just didn't know that particular way.  I followed the cam installation instructions that I found in the FAQ section, thanks to Oldschool for pointing that out, and had the cam successfully installed in about 60 seconds.

Ridiculous.

Thanks again.  I'll be back later......with panic I'm sure.