Replace timing and mag chains - Atlas

[madcity_binx]

Hi folks,

Is there a way to change the timing side chains on my 64 Atlas without taking the head and cylinders off? the main questions I guess is - is there a way to fix the engine in place without using a bar to run through the small end of the con rods (as suggested in manual)?

all insight and suggestions appreciated!

binx

[L.A.B.]

The alternative (if the engine is in the bike and everything connected up?) is to select top gear and then apply the rear brake while you loosen everything, as that should hold the crankshaft.

Take extreme care not to apply more force than is necessary to loosen/tighten the camshaft sprocket nut as the intermediate gear spindle is side loaded by the leverage and can loosen in its boss as a result.
Ideally the outer end of the spindle should be supported, preferably by holding it with a cut-down scrap timing cover screwed in place.

[madcity_binx]

Thank you LAB. I'll have the rear wheel on this weekend and can give it a try! I keep hearing about this cut away cover...I'll have to hunt one up.
Roughly how much torque is too much? Does it get transferred through the chain to the other spindle?

 
binx

[L.A.B.]

Roughly how much torque is too much?

I couldn't say exactly, as I don't know how tight your cam nut will be? There was no factory torque figure given for that nut -even for the later Commando models!!    

Does it get transferred through the chain to the other spindle?

I don't quite know what you mean by "other spindle"? If you mean the magneto, then - no, or do you mean how does loosening the cam nut actually side load the intermediate spindle? In which case - yes, the intermediate gear will be held static by the (locked) crankshaft gear, so any turning force applied to the cam nut will be transferred to the intermediate gear and spindle by the chain which will try to pull them sideways, and  this can damage the spindle drilling in the crankcase boss.
A firm steady pull on the wrench/spanner is needed to loosen (or tighten) the cam nut to lessen the amount of  intermediate gear side loading, do not attempt to shock it loose by hitting the end of the wrench with a hammer.