SOHC.co.uk Forums > CB750
Oil pressure issue / motor rebuild
Trigger:
Have you got the head and barrels to part company ?
MrDavo:
The head and barrels are apart, yes, but the barrels are still very much part of the upper crankcase.
I was getting perilously close to doing real damage, and I don't see why it won't go back together the way it came apart. It makes it more difficult, but not impossible, in race paddocks (and cars) bottom end issues are often dealt with like this to save time.
BTW your engine stand is turning out to be an essential. I noticed the first pages of the Honda manual shows a sandcast motor in something very similar.
Trigger:
sorry, I meant the barrels to the crank case :)
Trigger:
--- Quote from: MrDavo on August 15, 2016, 10:41:01 AM ---A busy day Sunday. I polished the cam cover at last, stripped the carbs for an ultrasonic bath and the choke linkage for a replate.
I also removed and stripped the oil pump. The rotors and their fit together are like new, with slight scuffing, but the endplates are badly marked up. Some scratches in the body but not much. Trigger, are these toast or useable?
--- End quote ---
I was building up some pumps today and have a chance to show you what a good pump looks like.
MrDavo:
Well the hiatus in this thread was due to me testing my engine building skills touring the north coast of Scotland on my Sportster, with its brand new crank, rods, cams and bushes. 1700 miles later, and no more noises than it started with. Here she is on Skye:
In the meantime, Trigger has sorted me with an oil pump rebuild kit, and Ashely has kindly sold me his spare crank which turned up via courier this morning, in enough packaging to wrap an oven:
To my great surprise, as per the instructions on the Honda crank bulletin, when I tilted it to the light, I can see the scrawlings on the crank, AAAA a squiggle in a circle, then 4444. I need to check the rods for markings, and at the weekend we will use a calibrated mike from Ed's works to check all the measurements, but as the cases are BBBB it looks like I will need a set of green shells for the mains.
My 2 assistants who helped me pull the motor and I all wrote dates on the garage wall to predict the refitting date, Ed the engineer picked the earliest date and is quietly optimistic. Last night I dropped the carbs off with him for a go in his ultrasonic bath, and the choke linkages to get zinc plated. We were intrigued by the little sprung trapdoors on the chokes, I'm guessing this is to stop a backfire blowing the carbs off. Nothing that fancy on an Amal!
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