Cam sprockets position for reassembly XJ550

I am in the process of rebuilding a Seca 550 engine but when I removed the cams and sprockets a few years back I didn't properly mark them. Now I don't know which sprocket is for the intake cam and which is for the exhaust, or what the small dots on the sprockets are supposed to line up with. I understand the procedure for aligning the cams themselves - dots on the cams themselves aligning with the dots on the cam caps at #1 cylinder TDC, but do the actual dots on the cam sprockets have to align specifically with anything? It seems like either sprocket will fit on either cam and also that either sprocket can be installed in 2 different positions 180 degrees apart to the other. Also, it seems like one sprockets' dot is very slightly offset from the position of the dot on the other. Can any expert (Fits, Dave, Chacal) weigh in? I can post pics if needed.

 

Looks like you cannot match the witness marks with the cams and sprockets, as they look the same. Put one sprocket on top of the other one, if they match up with the bolt holes and teeth they may be interchangeable the experts might know if that is possible.

 

https://www.cmsnl.com/yamaha-xj550-seca-1982-c-usa_model8858/partslist/A-10.html

Both sprockets have the same part number. Makes sense from a manufacturing point of view. Only the camshafts have different part numbers which they have to for the cam positions on the shafts to be different. Look at the picture it shown the sprocket and cam positions.

 

Thanks for that tip - I didn't notice any "shadow" from the mating face of the camshaft but I'll look now.

 

If you sit the cams in their bearings without caps at the TDC position if you have a Haynes manual you can check with the schemetic I posted the positions of the threaded holes for the bolts and the sprockets, might give you the solution. The witness marks should line up with the bosses on the camshafts. The sprockets are definately the same part numbers.

 

Yup, no witness marks whatsoever on these sprockets.

Witness marks? Dunno why but this engine's sprockets seem to have no such "shadow" of the mating surface of the cams they came from.

 

No solution there then. If you have a Haynes manual follow that. If the sprockets and the bolt holes match up they must be interchangeable. And if you set the pistons 1 and 4 at TDC and install the cams as per the Haynes manual you cannot get the timing 180 degrees out the bolt holes on the sprockets must line up.

 

I don't know what there are no shadow's on your sprockets either, mabe heat cycles cause it not sure. Remember you are timing the camshafts not the sprockets, I don't see any timing marks on the sprockets. Mabe others will chime in with some more advice.

 

Thanks for your help - at least I know which side mates to tha camshafts; the one without the “dots”. Wondering what the dots are for.

 

Best to check the manual regarding the dots.