Has anyone had any issues with runout on the drive side of a Commando crankshaft? When I put a DTI (clock) on the O/D of the crank where the rotor fits and turn the engine over, I get a 3 thou runout. Obviously these cranks were made on old clapped out machine tools back in the day so the tolerances were never going to be brilliant but does anyone know if this is a usual figure? When I fit the rotor & clock it up on the O/D the runout goes up to 10 thou, causing clearance issues with the stator. I`ve tried different rotors and non of them are that good. I did have a drive belt jump off and shred up, winding the reinforcing wire around the rotor and wrecking the stator so i don`t know if this could have possibly bent the end of the crank but there was a new stator fitted just before i bought the bike so it could have had this problem before I got it.
Has anyone else had this problem?
My old 'track day' Atlas…
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I've had two problems in…
I've had two problems in this area of the engine. Firstly, the stator was not mounted concentrically to the rotor and secondly the rotor magnets coming loose from the rotor hub. When checking for rotor to stator gap I've never noticed any discernible run out.
The oscillating rotor will create additional vibration and also additional stress to the drive shaft and mounting studs. Obviously, 0.010" run out at the rotor is totally unacceptable.
I think you're right suggesting the belt coming adrift is the cause of the damage. This would have occured due to the gearbox mainshaft and engine drive shaft not being square to each other in two planes, a common problem I believe. You're better off getting the shafts square wether you use a chain or belt.
I don't know if you can straighten the shaft without risk of it failing in use. You need to speak to somebody like Dave Nourish (01572 722712) for advice, or get a replacement crankshaft.
Simon.
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My old 'track day' Atlas once had a very bad piston seizure which locked up the engine (and rear wheel) at high speed. This obviously gave the crankshaft a hard time as afterwards the alternator rotor clearance went down to just 4thou on one side. No amount of adjusting helped, including a different rotor. In the end I ground away at the inside of the stator to get a reasonable running clearance.
On another engine, I once checked out the run out on the timing side and was amazed at how bent this end of the shaft was. How the timing cover oil seal kept pressure in the feed system is a mystery. Did it???