Fly wheel run out - R80 (1985)
Posted: Tue Jul 03, 2018 12:19 pm
Hullo 
I am installing a (new to the bike) 2nd hand flywheel. A few years ago, the starter got stuck ‘on’ and chewed up some of the flywheel ring teeth. Transmission has subsequently been out – so I decided whilst in there, to replace a few seals, etc, and ….the flywheel. I am unsure about a couple of issues:
1) Flywheel run out
After installing the flywheel, I measured 0.18 – 0.22 mm axial run out. I used a decent dial gauge (0.001 mm). If I pushed in on the flywheel to compress end play of the crankshaft, I got 0.03 – 0.05 mm additional movement. Although this could be used to reduce the total amount of run out measured …it still doesn't bring the measurement within acceptable limits.
The limit for radial run out is supposed to be 0.10 mm.
I have not come across a limit of axial run out for the wheel.
I am confused. I measured the axial run out because that is what seemed to be described and illustrated in both the Haynes and Clymer manuals. But the value for that flywheel run out is referred to a radial run out (which I didn’t initially notice being a relative novice at this particular type of measurement).
I’m not sure how I would measure the radial run out - and if indeed that is the run out type that is important (the issue being engine vibration). Am having difficulty locating any clarification on the Internet – anyone know about this stuff?
2) Balancing the package
Before removal, I marked the clutch plates and the original flywheel together as a package – for balanced reassembly. Replacing the flywheel meant that a part of the package was different to what came out. I put the engine at TDC and then inserted and torqued the flywheel onto the crankshaft boss so that TDC marks appeared correctly in the engine case timing window. I then put the clutch pack back in, aligning it’s marks and the flywheel’s with a correlating mark I had put on the inner engine case. Seemed the best thing to do – other than taking all the components to a machinist/engineer to balance them.
How much of a difference does it make (vibration or other problems?) if the new flywheel is not pre-balanced with the clutch pack it is married to in the engine?
I guess what I am really asking is how much attention do I need to pay to flywheel run out ?
Many thanks for reading – Stenton
I am installing a (new to the bike) 2nd hand flywheel. A few years ago, the starter got stuck ‘on’ and chewed up some of the flywheel ring teeth. Transmission has subsequently been out – so I decided whilst in there, to replace a few seals, etc, and ….the flywheel. I am unsure about a couple of issues:
1) Flywheel run out
After installing the flywheel, I measured 0.18 – 0.22 mm axial run out. I used a decent dial gauge (0.001 mm). If I pushed in on the flywheel to compress end play of the crankshaft, I got 0.03 – 0.05 mm additional movement. Although this could be used to reduce the total amount of run out measured …it still doesn't bring the measurement within acceptable limits.
The limit for radial run out is supposed to be 0.10 mm.
I have not come across a limit of axial run out for the wheel.
I am confused. I measured the axial run out because that is what seemed to be described and illustrated in both the Haynes and Clymer manuals. But the value for that flywheel run out is referred to a radial run out (which I didn’t initially notice being a relative novice at this particular type of measurement).
I’m not sure how I would measure the radial run out - and if indeed that is the run out type that is important (the issue being engine vibration). Am having difficulty locating any clarification on the Internet – anyone know about this stuff?
2) Balancing the package
Before removal, I marked the clutch plates and the original flywheel together as a package – for balanced reassembly. Replacing the flywheel meant that a part of the package was different to what came out. I put the engine at TDC and then inserted and torqued the flywheel onto the crankshaft boss so that TDC marks appeared correctly in the engine case timing window. I then put the clutch pack back in, aligning it’s marks and the flywheel’s with a correlating mark I had put on the inner engine case. Seemed the best thing to do – other than taking all the components to a machinist/engineer to balance them.
How much of a difference does it make (vibration or other problems?) if the new flywheel is not pre-balanced with the clutch pack it is married to in the engine?
I guess what I am really asking is how much attention do I need to pay to flywheel run out ?
Many thanks for reading – Stenton