Primary chain

I own a 1983 XJ750.
I have owned it for approx 2 years.
Mileage is unknown as the odometer had been replaced by PO.
There is quite a loud noise from the front of the crank case and I assume it is the primary chain that is slapping during idle and gets quieter when the throatle is opened up.
Has anyone experienced a primary chain failure? And if so, does this cause immediate drivetrain failure?
I have completed a couple of oil changes, and have not found any plastic guide remanents, it still shifts, (slightly hard from nuetral to first, since changing the oil to semi synthetic) although it could have disintergrated long ago.
The magnet has during the oil change, contained a coating of ultra fine metallic pieces.
Any advice from you experts is greatly appreciated.

 

Those fine metal peices are a telltale. When the primary chain guide goes the chunks will sometimes get ground to tiny bits by the transmission gears. Once the guide is gone the primary will slacken enough to run against the oil nozzle that lubricates the primary chain.

You won't have drivetrain failure (the primary chain on the shaft driven XJs only spin the alternator shaft), but you will continue to wear out an oil nozzle that costs $100 new (used tend to go for less; a lot less if you get lucky) and send bits of steel through the engine (which can potentially lead to cam bearing failure). When I pulled my engine for the same problem I found the oil pump screeen 1/2 covered with plastic from the guide, a few big chunks of guide rattling on top of the transmission gears, and a very wide space between the guide mounts where the rest of the guid had once been. The oil nozzle was nearly worn through to the oil passage.

You can ride it for a while, but I would plan on opening the engine up soon; like before the fall soon. If you have had this problem the entire time that you have owned the bike then I would suggest that you park it until you do the work.

 

+1. Exact same description. I thought k-moe was talking about my bike there for a minute. Imo don't take a chance on ruining the mill. Park it until you can fix it.

Gary H.