So I lost my first day of sleddin because of this thread lol.
I pulled my drive system apart ('bin thinking about grease at 850 miles anyway and I wanted to find out why my top pulley bolt doesn't stay torqued). First I want to say, everytime I get into this Poo I am impressed with the quality of parts and excellent design.
Every bearing is NTN from Japan (and standard sizes). The jackshaft is light (with quite a lot of work in it's design) and very strong. Those 2 things alone are much different from my last sled.
To pull it apart was as simple as take off both belts, the secondary, and 3 bolts for the clutch side bearing cup and out it came. Doesn't get any simpler. Under 30 min. first attempt.
I even found a piece (the 3 nuts attached to a bracket for the bearing cup thingy) where Poo welded steel to aluminum lol. How do they do that?
Here's what I found.
First, I removed the belts, pulley and secondary. I thought i noticed a bit of a "sprong" as I unbolted the pulley so I kept that in the back of my mind. I spun the jackshaft and it was a smooth as silk. I might not even grease it I thought.
Then i pulled off my glasses and had a closer look and I saw the jackshaft spinning but not the bearing (QD side). Hmm.
Started poking in deeper and found a couple of little concerns. First the top of the "QD plate" is not very rigid on it's own. It needs to be torqued sold to the jackshaft to have any strength.
Second, on mine I needed to push in quite a bit to get the bearing to bottom on the machined bearing stop on the jackshaft. This design needs the inner bearing race to be secured to the jackshaft through torque on the ends or the shaft will spin and not the bearing.
Third, I think Poo's glue guns are getting old. My QD plate is unglued in spots and the glue feels like old gum. I looked at the bolt design and figure it will be a summer project to reglue. Not concerned at this point in time.
So I pull the jackshaft to look for galling on the shaft or bearing. Found a bit of discoloration on both. Bearing showed it had been secured slightly cocked for the last bit of time. Micrometered both and compared to a new 6205 I have in stock lol. Not enough difference for me to measure but there is no interference fit here. They are both (jackshaft OD and bearing ID) equal as close as I can measure (1/2 thouish).
I did retorque my top pulley bolt twice (once about 150 miles and once around 300 miles) and I do believe if i had not done this I would have seen extensive galling on the shaft.
So proceded to reassemble with a bit of "blueprinting". The bearing looked and felt fine. Maybe a C3 clearance now lol but I just regreased and left it.
I needed to make a 55 thou. shim for the jackshft to fit my QD plate position. I could have shimed either end of the shaft but picked the QD side. It has to be a special "homemade" shim because of the large radius at the bearing stop. So I chucked up a "close" shim and lathed it to fit.
Now when I bolted in my jackshaft it just touched the QD plate bearing as that plate fits in my sled BEFORE torquing up the pulley bolt.
I cleaned the surfaces and re-assembled using sleeve retainer high heat locktite between the bearing and the shaft and retorgued it to a tight position using some sleeves and a bolt to let it set. I don't know if this is necessary but it made me feel better lol.
Then I took my glasses off again to see why this happened on my sled. Many systems use the torque on the inner race to lock in the bearing. Nothing wrong with that but it cannot lose it's torque.
What I found with mine was the disc brake (it`s the sleeve-spacer between the bearing and pulley also) slowly had ever so slightly been mushrooming into the bearing. You could just see and feel the radius of the inner bearing race on that side. So even though it was only a 1/8th turn of lost torque it is enough to allow the shaft to spin in the bearing. You could also see movement had been happening on the wave washer and pulley surfaces the disc and washer contact.
I centered the disc on the splines and lathed off .60 thou. off the bearing side and 30 off the pulley side and replaced these distances with shims. This gives me much more contact surface to torque against the bearing. I also replaced the wave washer with a thicker flat washer so I could see if it comes loose easier and give me more contact surface to torque against too.
IMO Poo could improve this area with a few simple changes. Add a thou to the OD of the jackshaft, a little stronger plate or a couple of fasteners at the top of the tunnel, maybe a little handfitting in this area to shim jackshafts during production lol, better controls on the glue guys lol, or two birds with one stone; Make a hardened sleeve to fit between the bearing and pulley and let the disc FLOAT on that sleeve.
Moral of this story; check your top pulley bolts boys. Check them twice.
