Wednesday, October 13, 2010
Wednesday, October 6, 2010
The next project in the shop is rebuilding a 1971 CB350 into a true biz cafe racer for a customer. We agreed on a look for the bike, and the work began. The first thing I did was to build a stainless 2-1 exhaust while I had the bike together. The bike was in fairly rough shape when purchased, though the body work looked alright, the tires were flat, shocks were mush and tank was full of kreem covered rust!
I got the bike up on a stand and waited until I had some time to work on it, then I stripped everything off that wasn't going to be part of the completed bike or wasn't in good enough shape to keep.
Before doing any body work, I decided it might be a good idea to go through the engine and do a thorough reconditioning, along with replacing any parts that were worn past service limits. Pulling the engine was very easy, once I removed the mounting bolts, the motor lifted right out of the frame.
The engine turned out to be pretty rough too. When we changed the oil after getting the bike, we cleaned a mess of metal shavings and chips from the oil filter (not a good sign). Assuming it was probably a chewed up tensioner, we hoped for the best. Turns out the engine was chewing itself to bits and the previous owner probably thrashed the hell out of this bike. Going through the top end, I discovered the cam was badly pitted on the lobes, the rocker arms were also ground down due to the pitted cam, the cam chain was stretched probably because of the added friction, the tensioner was indeed chewed to bits. When I got the head off, the condition was less bad, the valve seats looked serviceable, though one of the exhaust valves was too pitted to get a cup on for lapping.
One of the combustion chambers also showed some damage from what might have been a foreign object, but the valve seats weren't impacted, so the piston and head could still be used. Looking at the cylinders, I thought they were serviceable, until I did a hone and discovered some deep scoring that will require at least a .25mm overbore and piston kit to match.
Cleaning up the parts was pretty simple, and facing the mating surfaces will ensure a good seal and proper reassembly. Once replacement parts are approved by the customer, rebuilding can proceed. The good news is basic inspection of the bottom end showed splitting the cases will probably not be necessary. And my advice is to replace the cam chain with a heavy duty type with a rivet master link so the chain can be upgraded without splitting the crankcase and involving that much more work.
Sunday, September 26, 2010
Wednesday, September 22, 2010
|CB360 cam adapted for needle rollers|
|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
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
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.