Topic: Replacing crank & rod bearings without removing top end.

[HondaMan]

In a post a little earlier I mis-wrote about this topic, as I had this bike on my mind: that post's owner was asking about changing the cam chain without removing the top end, which isn't possible with an endless chain. In this engine, the crank bearings all need replacement from wear as it causes low oil PSI when sitting in hot traffic. It is possible to do this without removing the head and cylinders, so I'll show that process here as I go.

Today: I removed the engine from the frame and removed the cam. I'm using the [recently] "windowed" cam cover to protect the top when i flip this engine upside-down. Pics at 11...

[grcamna2]

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[70CB750]

In a post a little earlier I mis-wrote about this topic, as I had this bike on my mind: that post's owner was asking about changing the cam chain without removing the top end, which isn't possible with an endless chain. In this engine, the crank bearings all need replacement from wear as it causes low oil PSI when sitting in hot traffic. It is possible to do this without removing the head and cylinders, so I'll show that process here as I go.

Today: I removed the engine from the frame and removed the cam. I'm using the [recently] "windowed" cam cover to protect the top when i flip this engine upside-down. Pics at 11...

Following. 

I remember reading about this for the AMC 258.  Using a dovel in the crankshaft oil hole to slide the bearing out and slide new bearing it.  The top half, of course. 

[MauiK3]

Interesting, I suppose if the top end is known to be ok doing this makes sense.

[HondaMan]

OK, some pix and a little 'side trip' from a decade ago:
The first shot shows I've removed the cam and rocker towers, then put an old (my "windowed" version) cam cover on to protect the good one, as I don't want the good one scratched up by flipping the engine over (I don't have one of those fancy engine stands!). I'll be working this one on the floor...

The 'side trip' is: look closely at the cross-crankcase oil port that oils the transmission in this picture, and you'll see a screw head slot where the rubber plug is found in K2 and later engines. When I rebuilt this engine years ago for its owner, the left side of the engine was an oily mess (like the K0/1) because of weepage thru the gasket of hot crankcase oil against the paper gasket. The rubber plug was missing! Honda didn't even sell the part then (CMSNL has found a few these days) so I ended up drilling and tapping the hole 1/4-28 and then cut off a 5/16" long bolt, grooved a screwdriver slot into the head, and Loctited it into the hole to stop the weeping. It worked!