Seven Fifty cafe-racer. Engine, part 2.

Ok, let’s continue engine section. As I wrote in previous part, in addition to CBX750 parted engine I also bought CBX750 wiring, ignition unit, handlebar switches and other units of electrical system.  I had to bake exhaust downpipe coated with ceramic on the bike and it occurred to me a good occasion for CBX electrical system testing. Firstly I ran engine with stock Seven Fifty electrical system, then I installed CBX pulse rotor and generators, plug CBX wire harness and started engine again. It rand good and sounded even better than with stock Seven Fifty electrical system.

After some time I stopped engine to refill small can tied to left handlebar with fuel and then tried to start engine again, but it won’t  start and to my surprise, starter rotated engine as if there were no spark plugs installed. And that may meant only total lack of compression in cylinders…

I spent some time for optimizing CBX wiring (I’ll write it later in separate post) but as I have got a positive answer for my question about CBX electrical components operability there were no reasons which may delay Seven Fifty engine disassembling.

In fact I had intention to disassemble engine, put out all “guts” for checking but to install empty “shell” back into the frame to have a model which helps me to work out last components I didn’t designed earlier.

I prepared Seven Fifty to engine removing:

But firstly I just opened valve cover and I immediately saw there the reason of such a strange compression disappearance.  Intake camshaft sprocket bolts  were unscrewed and sprocket flew of its seat, as a result cam chain became loosened and crankshaft sprocket began to slip on it.

And here is one of cam sprocket bolts. Another one I found near it too.

The reason of such minor accident is that one of previous owners used non-original bolt to secure the sprocket in its place. Another bolt was genuine, but it could not help either. Here they are: two on left side are the bolts I found in cylinder head and two on right side are the original Seven Fifty and CBX 750 cam shaft bolts.

That’s a miracle, but as a matter of fact, nothing except upper cam chain guide was damaged. I suppose sprocket flew out right when I pressed “Stop engine” switch.

This sprocket bolt was not the only one non-original hardware I found. Half of camshaft holders bolts were changed and couple of original ones were so over-tightened that they broke when I began to unscrew them.

Though, other cylinder head parts looked like they were intact, camshafts themselves and their bearing surfaces looked good. Anyway, I have intention to use CBX750 cylinder head and camshafts so I placed CB750 cylinder head on the shelf and continued my work with engine.

Before I took the engine from frame I freed some space on my shelves and prepared my “engine assembling” workbench.

Engine was placed on my second workbench for more ”rough works”  where I disassembled it.

There was nothing unusual in this work. Of course I had to make some ”special tools” to screw clutch basket nut but those, who work with Honda motorcycle became used to such features and strange engineering decisions, when you must  grow a third hand or help yourself in another way…

As I wrote earlier, there was nothing special except what I found under ignition cover. I got used to situation, that my work on engines is not only that of customizer, but usually also engines restoration. But looks like this particular engine may be a toughie.

But this all is just e matter of expenses and illustration what happens when one  tries to fix things without  knowledges and repair culture. It is not even post-Soviet feature, but  an international problem.  And anyhow, my goal is to sort out the situation with this engine  in the best way.

I have CBX750 good crankcases at hand, but I should  learn if there are any significant differences between CBX750 and Seven Fifty parts. That sounds like a good theme for my next technical post.


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