This will be a great discussion. When we look at the stock Honda pilot bearing we see marking on them. We also look in the manual and we see service limits. We also see recommendation on items like oil to gas ratio. Yes these were set back iin 89/90 and oil development in two cycle oil been improved. Most of the time we just thank of the piston lubration. Yes bearing as well. As we (I) changed from 20 to 1 to 32 to 1 or other oils and ratios via a higher grade of oil. I considered a few things. First of all I use HP-2 from Honda at 32 to 1. We and most have seen failures from loss of lubrication in one way or another. Heat build power and it also stresses parts like bearings. I know, get to the point.
Lets look at the marking on the bearing. Manafacture, size and type. The mfg name tells us were to look for the data, the size tells us the fitment and the type in this case of the c3 rating tells us clearances. The clearances of the c3 is the choice for the application in stock trim for the pilot. The bearings fit tight ( press fit, case ID smaller than bearing OD) in the cases and tight on the crank shaft ( Shaft OD greater than Bearing ID),if in good shape and or new.
The manual ( 9-1) gives us the numbers for parameters of the crankshaft which is a related part to the bearings. Theres some more to factor in but not in the manual. All of these numbers play a part in the operation of the bearing. The manual also fails to tell us the operating speed of the engine however Honda sets a rev limiter (somewhere around 7600 rpm) in the CDI another factor in the bearings use. Another interesting factor is load and as most know the 350 has no torque limiter in the transmission like the pilot to act as a buffer to the load. Yep the trans has bearings as well.
Though out some babble, looking at the numbers on 9-1 and thinking in your head what does these mean as the crank assembly rotates ( 2 radians=360 degrees). The first thing to pop in my head are run out or wobble as it rotates. This will also load to the main bearings as the shaft moves up and down and side to side in the bearings bore axis. This wobble is like unbalances wheel on a car. The clearance built into the bearing takes up some of this axial movement in a radial motion. Now you see why the Nissan axle bearing is a subbed for the c3 rating is a fitment for the application. You can also see why the bearings either spin in the case or come apart based on crank run out. One can also make a assumption that the end play (thrust) and radial clearance on the rod and its bearing assembly can play into this as well. Since the crank is pulled tight into the clutch side case and then the flywheel side is installed the clutch side, it the alignment within these numbers related to the rest of the parts installed. Now you have a frequently ask question as to why Honda only put alignment dowels on the clutch side case and the cylinder is made for their fitment. The bottom end assembly and related crank numbers is another discussion so I'll skip that babble.
What if we installed a Cn or C2 in place of a C3. First we need the clearance numbers to determine fitment. in the case of radial clearance it would be the distance between the four contact points within the bearing, up and down if you will. For axial we need to know the amount of lateral movement theirs is between the inner and outer race, in and out if you will (SEE PIC ). These numbers must come from the MFG unless you got one heck of a shop I know I don't. Remember where talking about the deep ball grove pilot bearing. Again you can visualize in your head how a out of round crank can exert forces on the bearing to lock it up until something gives. Now let?s look at the two cycle oil used for lubrication. Yes back to heat and its dissipation. The oil is used to take heat away from the bearings cause by friction forces. Imagine if you will at let?s say 5000 rpm that bearing is spun 2 radians ( 360 degrees) at 83.33 times a second 5000 (revolutions per minute) /60 (seconds in a minute)= 83.333. Yes that hauling a _ _. Now exert the additional load of the out of spec crank assembly. How much oil is needed to shead the heat until it reaches is self destruct point. Well not long if it exceeds it class of clearances. Now time for a quick fact related to the Honda specs. If memory serves the C3 is a 10,500 rpm bearing, which is rated around 75% so lets take 10,500x.75 and see what we get =7875. See any correlation yet. Should I even mention max piston speed for the pilot at its bore and stroke again another discussion. A quick note related here is the square bore and the force excreted on the rod and bearing assembly further compounding the axial clearance. Heck what if the cases are not parallel to the bearing that number must be factored into the total equation. One will compound the other and the effects show up on the crank,guden pin, piston and cylinder. As it rotates up and down if the clearances are exceeded force is being applied to the tight parts until they self clear which are wear indicators like scuffing, marred pins ect. You need to know how much you have to play with TDC to BDC to make sure it can handle the stresses of the increases in load. As it get hot thing grow and there a lot of part, use of those parts that can effect it all the way through an engine build. You here thing like velocity density port time area angle area , rpm , pipe tune, CCR ect.
As we discuss a change in the bearing let?s look at the clearance number for the bearing being used and under what engine parameters.
More later, need to head to work. Man I love this stuff thanks for the opportunity to share and discuss.
