SOHC.co.uk Forums > CB750
roller bearing vs. swinging arm bushes?
Phil:
That brings back memories! Regret no pictures - all I have is a front sprocket! I like your Japauto and some of your ideas are great. Strengthening the frame around the engine mountings is a good idea. In the early days we used to think the flexing was the swinging arm - hence people fitting Dresda box section ones. Now they know the original swinging arm is fine in terms of flex. The factory heavily braced the top two tubes between the shock top mountings. The metal quality of these frames was/is terrible. I have a K7 frame which I have cut up and the wall diameter is paper thin in places and not through rust. It is also rusted right through in other places because condensation forms inside these tubes and they rust from the inside. The welding around the headstock is also terrible. Tubes are rammed into other tubes and held in place with a couple of spot-welds! Some of the serious CB750 racers had new frames made to the exact dimensions of the originals - but made of top quality tubing. The frame design/ dimensions are fine, it's just the crap materials I think! I would love to see more pictures.
Phil
Voxonda:
One point of consideration might be, what people expect from a surtain design, and what they want to do with it.
In my opinion, the CB750 was never really intended to be a all out racer! In those days from a marketing point of view, it had to be! But it could never really live up to the expectations. Though fast, it was a bit unreliable when "highly" tuned. In endurance, with milder tuning, it was top of the bill. Even when fitted with big-bore kits. One of the weakest links was, and still is, the camdrive when fitted with race-camshaft.
In present days people tend to overdo tuning while only 'parade' or so of and on a classic trackday! Really think that for these purpose a standard engine with good (total loss) ignition, exhaust, loose the heavy dynamo and fine tuned carb's will do the trick! Bonus is that everything will stay in one piece. Personally I focus on getting it round the corners, though I am no #1 racer.
Cheers, Rob
PS.Will show some pictures shortly.
Voxonda:
Hey Phil,
Here is a picture of the rear top engine mounting. Makes it a lot more rigid. just have to give it a blast and a paint.
Am just starting up a little business in developing and producing some hard(er) to get items for our beloved bike(s).
Cheers, Rob
Voxonda:
This is the front engine mount, made of 7075 Aluminium.
Please let me hear what you think.
Cheers, Rob
Phil:
Your stronger engine mountings look much better than the originals - this is a real area of weakness! I wanted some made in 7mm titanium (I have the plate) but am struggling to find a machine shop that can do the job - same story trying to get Ti engine bolts, wheel spindles, swinging arm spindles etc. Nobody wants to work with the stuff! I am interested in your swinging arm bushes - what is the price? Also, your spin-on oil filter is pretty neat - did you make the holder? Do you make a blanking plug for the kick-shaft spindle? Phil
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