Cyoool!!!
I’d love to see video of your road test.
I’d love to see video of your road test.

























I have had pretty good success with using Torx bits as screw extractors. Just drill a slightly undersize hole and tap the Torx bit in. Sort of a poor man's Ridgid/ Ridge Tools extractor. 12 point XZN bits may also work, possibly better.This is a bit out of order but progresss.
Mounted the lower engine case in the mill and overbored the flogged out holes then turned some solid stock to fit. Slugs in situ before welding.
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I was wondering how to fix the less flogged but also loose frame bosses. The frame is too big to fit in the mill while contemplating this my Brother in Law appeared like a fairy godmother and gave me a set of adjustable reamers. He said he hasn't used them in years and they were all carefully sprayed with soft seal to stop them rusting.
The plan was to take the bosses out to 14mm and use glycodur bushes to take them back down to 12mm.
It worked ok.
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Then using the front case mounts and a quickly made punch guide I was able to use the frame to mark the slugs for drilling . So back to the mill and another little reem and the job is done.
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This is the good looking side the other hole is not even close to concentric.
I have spent a great deal of time on the flow bench since the last update.
The plan is to use stock valves and cam.
First up was testing the 750 head in stock form, it has the same cam lift and valve sizes as the 850. The throats stock are around 85% of the valve sealing diameter on both the 750 and 850 and that’s where I believe it should be.
After a quick cleanup of the ports just removing the tops off the casting lumps another test showed minimal change as expected.
I then opted to do a pocket port making the transition from the throat to the bowl smoother. All up about 5 mins work with small burr, then re test.
The gains were so great I did doubted my testing and repeated the tests a few hours later with near enough the same result. Great stuff however any further work I did reduced flow so I now had a plan and thought it would be easier to make the 850 head flow well in no time at all.
The 850 head is a later design, and stock it flows as well as the 750 head I had played with. For those of you with 750’s a 850 had will not fit 750 barrel but the good news is its very easy to get some decent gains on the 750 head.
I did a cleanup as before and retested with no real gains, so blended the bowls and got a small increase in flow. Nothing like the 750 head.
I then had an inlet valve back cut and again got a small gain at low lifts but very small, then looking at the head it looks like the valve is shrouded. I checked this with a ball bearing the right size on a bit of welding rod and decided to de shroud the inlet valve and retest. I was going to loose compression slightly but the compression jump from 850 to 896 would compensate for that.
After retesting again there were very small gains at low lift and full lift but nothing in the middle where I wanted it. I decided to stop there rather than loose what gains that had been made.
I believe a multi angle valve job would help but that is not in the budget.
So after all that work I can say that at least it is not any worse than when I started ,slightly better than stock and as a novice will take that as a win and a lesson.
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To make resurfacing the head easier to set up I removed the cam cover studs and as usual all but one easily came out, the problem one stripped the threads on the stud. Put a nut on and hit it with the welder and the stud came out with its hands up.
The head has been skimmed now to clean up a few imperfections in the gasket surface, my mill and flycutter are not rigid enough for a head that size. 0.2mm was taken off roughly 8 thousandths.
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I also bought a valve refacing machine it works but the wiring could do with a revamp, this will speed up experiments with back cuts on valves and I will use it to do the 850 valves which are not in a good state. Just about every Garage had one of these when I was young but now they are a bit of a rarity.
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I will reface the valves and lap them in the head. Then clean up the cases and hea a few more times to remove blast media etc then mask the gasket surfaces for painting.
Next up after finishing the cases is removal of the broken bolt from the gear shaft. My plan is to use the lathe centre drill then reverse grind a bit and wind it out . Like most things on this motor it wont go like that but that should be the last of the remedial work fingers crossed.






