Topic: cam sprocket alignment cb350

[Gittfiddler]

Hey all,

just got done with a top-end rebuild on my 72' 350 twin.  what i found after having to yank the motor twice is that...
 the camshaft & sprocket has enough movement before the side bearing housings are installed to allow the cam chain to skip teeth on the crank sprocket.  so you can have perfect sprocket position then slide the cambasket onto the head, install the shaft, rockers, pins and side housings and then the chain has skipped.  to save some frustration in the future, with the basket on & the shaft bolted to the sprocket & the left cylinder set at tdc, before slipping in the rockers etc. you can let the shaft down an actually skip the chain so the sprocket mark is at 12 o'clock.  then keep constant upward tension on the sprocket & chain slip in the rockers & pins and the bearing housings and maintain the proper timing position.  You will have to turn the crank to get the rockers in but if you keep tension on the chain you won't slip and have to take the engine out of the bike and tear it down when the valves smack the pistons.  hope this makes sense and helps some one.

[lordmoonpie]

Hey all,

just got done with a top-end rebuild on my 72' 350 twin.  what i found after having to yank the motor twice is that...
 the camshaft & sprocket has enough movement before the side bearing housings are installed to allow the cam chain to skip teeth on the crank sprocket.  so you can have perfect sprocket position then slide the cambasket onto the head, install the shaft, rockers, pins and side housings and then the chain has skipped. 

Might be a daft question but did you have your camchain tensioner in by this point? With the tenioner in I've never had this problem but without it, the chain can slip merrily around. From memory the Haynes manual says to put the tensioner in too late for my money and this is the problem you get as a result...

[Gittfiddler]

did not have the tensioner in as per Haynes.  what i found was that is was kind of handy to be able to skip teeth to get dead on before installing the rockers & side units.  having the tensioner engaged at that point might make it somewhat difficult to get the camshaft ends into position to slide them in without pounding.

[lordmoonpie]

did not have the tensioner in as per Haynes.  what i found was that is was kind of handy to be able to skip teeth to get dead on before installing the rockers & side units.  having the tensioner engaged at that point might make it somewhat difficult to get the camshaft ends into position to slide them in without pounding.

Yep that's true it's easier but you get the chain slip. If you put the tensioner in you can still rotate the cam until you can get the lobes to lowest point positions against the installed rockers and sides. There is a place for both sides around the rotation of the cam with tensioner installed, where each side goes on with just finger pressure. Try it out to get the hang of it (both sides are loose at a different position naturally as the lobes are different. Worked for me every time