Sunday, September 26, 2010

1974 CB 360

After bending two intake valves due to a loose tappet lock nut, I am finishing up reassembly of the 360 engine, I made some improvements to the bearing setup as well, notably the stainless sleeves on the cam and a change to the shim system used to keep the cam lined up with the rocker arms.  I cleaned up the pistons and inspected for any cracking due to the valve collision, and none was found, nor were the wrist pins or conrods bent or damaged, so I got off fairly lucky.  I reringed the pistons and renewed the base gasket sealer (not running a base gasket) and installed the block.  These bikes are nice because you can to a complete top end rebuild with the motor still in the bike, which saved me at least a few hours of work.

I bought a new copper head gasket for the motor as well, from Lani at copper gaskets unlimited, he fixed me up with a .050" gasket and already had the pattern for the 360 on file, so I was happy.  I sprayed both sides of the gasket liberally with copper gasket spray, waited about an hour and then installed the gasket, everything lined up nicely so I was ready to install the head.
A friend donated some old cb350 intake valves, and since the guides and seats were fine (seats were a little damaged, but not enough to affect the seal), I lapped in the valves using Goodson 280 compound, and reinstalled the valves.  I checked for seal by putting the head on its side and filling the ports with paint thinner, it has a low vapor pressure so it can find the tiniest of leaks to get through, and after a half hour, no drops made it through, so the seals were good.  I did some additional machining to prep the head, and installation went fine.

I had a spare 360 rockerbox laying around (I bought a used one for the rocker arms, as one of my old ones had what looked like a crack forming), so I cut it up to make a holder for the #1 intake valve rocker. This tool can be used to properly degree the cam without removing the rockerbox to adjust the sprocket.  The cam sprocket needs to be slotted so it can be adjusted in relation to the cam, this is necessary if you change the distance of the cam to the crank, as removing the base gasket does.  This modification bumps up engine compression slightly, and being able to properly degree the cam ensures the engine will still run well.  It's not a bad idea even for a stock motor, as the cam chain will stretch and retard the cam timing as it does.  Degreeing the cam is a fairly simple maintenance step to keep the engine running strong.  It's amazing what a noticeable change in performance even 1 degree makes.

Wednesday, September 22, 2010

1974 CB 360

CB360 cam adapted for needle rollers
Part of the rebuild for the CB360 engine at the shop included converting the cam to a needle roller setup, this involved having a friend machine the head to accept 28mm bearings, modifying the oil holes for the old bearings, and creating a new oil passage to the center bearing.  After riding a few miles, oil started coming out of the left oil seal and I found that the cam didn't have enough of a shim on the left side and was pushing out the oil seal, so I split the difference with the 1mm shim on the right side, and used two .5mm shims, one on each side.  After 300 miles, the engine was again pulled due to another issue, turns out one of the tappet locknuts came loose and backed out with the tappet, got stuck in a valve spring and siezed the cam, the camchain slipped over the sprocket and the pistons nailed the intake valves.  Because I had the engine apart, I inspected the cam and also found spalling on the bearings where they rode on the needle rollers.  Turns out the chill hardened cast iron of the cam isn't hard enough to run on needles, so the solution became machining some stainless sleeves to the original OD of the cam bearing, machining down the cam bearing to the ID of the sleeve, and heat fitting the sleeves over the original bearing areas.  After a few tests, it was found the stainless has much better wear properties and should last indefinitely.
machining the cb360 head allows for a larger
shim on the left and right sides of the cam,
this is better for the longevity of the shim

the installed cam without bearing shows
the machined stainless steel sleeve that
will allow the cam to ride on needle
bearings without causing damage
to the soft cast iron of the cam
I found that the head can be machined about .090" on each bearing side, to make it even with the valve cover sides, making it easier to install a thicker shim which should last longer.

After machining the head, the replacement intake valves were lapped into the seats and tested for sealing.  I used a method of installing the valve with spring and retainer, then resting the head on it's side and filling the intake ports with paint thinner, after letting this setup sit for 15 minutes, any tiny leaks will be apparent, as the thinner has a way of seeping through the smallest of pores.  A little condensation around the seat is normal, and can be seen if you dab at the seat with the edge of a paper towel, but any actual runs of thinner indicate a less than adequate seal.

Saturday, September 18, 2010

1969 CB 350

The Honda CB350 Vintage Fighter “Spitfire”  is complete, we took it around town with a photographer to get some nice shots of the work. 
This bike is an example of the kind of custom work Roc-City really strives for, a very minimal look with a highly developed form.  I spent most of the design time considering how to combine the necessary parts of the motorcycle to simplify the overall appearance, and still achieve a unique and eye catching result.  Not much on this bike is left over from the original donor bike, it’s actually easier to name the parts that are stock, such as the engine, frame and wheels.  The all aluminum bodywork is handmade for this individual bike, no templates or forms were ever made in producing the parts, and there were actually no drawings made before beginning the work.  When I began stripping the bike down, I really had no plan for the outcome, but let a mental picture begin to form in my mind as I created each part.  As the bike grew nearer to a finished piece, the design decisions became more critical, as new parts not only had to function themselves, but also had to work well with the look of the rest of the bike. Equally challenging was keeping the bike comfortable and safe to ride, features like the rear brake cable conversion and increased swingarm angle do a lot to improve the old bike’s handling and stability.  I’ve seen many custom bikes which pay little if any heed to the actual purpose of the motorcycle, there are probably hundreds of these barely rideable motorcycles filling gallery space and living rooms in the trendiest of circles.  I however, feel that a bike is only a complete piece when it is ridden.  The proof is in the pudding, I was riding behind the new owner of this bike as we approached 100mph, the bike handled and sounded great, I couldn’t have been more pleased. 
I see this bike as a step in a direction of design that I have begun pursuing, a departure from the aesthetic of the cafe racer, which, as a form necessitates functionality and speed, all else being secondary.  The development of the chopper also appears to have dead ended, having been careened into a heap of gaudy detail pieces and utter lack of composition and flow.  From somewhere in this mix, I hope to see a form of custom bike come forward that combines rideability with excellence in design, form and function being complimentary rather than in contest.  I imagine this form will draw heavily on vintage style, as I am myself attracted to designs from the past.  I have already begun work on the next project, and look forward to finding out where this path will lead.