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cb400a
Apr 6, 2021 20:05:23 GMT
Post by tucksie on Apr 6, 2021 20:05:23 GMT
Very interesting buster.
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Post by buster on Apr 9, 2021 15:37:31 GMT
couple more bits and bats arrived just need it to warm up a bit now so I can crack on
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cb400a
Apr 10, 2021 16:05:23 GMT
Post by buster on Apr 10, 2021 16:05:23 GMT
last time I snapped one of these studs I had enough of it stuck out so that I could run an m8 die down it, then nipped a nut on, then welded it in place and that let me apply an enormous amount of pressure to get the damn thing out (thread in tact that time). this time I wasnt so lucky, I tried the weld it up trick but frankly I was urinating in the wind, so used an old (knackered) set of barrels as a drilling jig and set about drilling the little git out I was hoping to rescue the original thread but its suffered a bit in the drilling process and a 'nearly' thread just isnt good enough for a cylinder stud so time sert it is then. the rest of the day was spent scraping gasket faces and cleaning individual bits and pieces (boring), this is exactly why engine rebuilds cost so much if you dont do them yourself
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cb400a
Apr 10, 2021 16:39:24 GMT
Post by buster on Apr 10, 2021 16:39:24 GMT
forgot to add, I also measured the camshaft lobes, they are the same spec as my 450 engine (36 point something mm) so now we know which parts bin they raided for the 450 cams
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Post by buster on Apr 11, 2021 15:13:54 GMT
so sprayed the starter motor body last night, then freshened the rest of it up today
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cb400a
Apr 11, 2021 15:19:46 GMT
Post by buster on Apr 11, 2021 15:19:46 GMT
then moved on to the crankshaft, theres no short cut that I know of with this job. its a case of strip the rods and shells then reassemble dry, check everything (all good on mine) then rebuild with nice new clean oil (I mix it about 50/50 with that lucas gloop for building engines back up). torque on the rods done in three stages 10 then 15 then 20ft/lb then bagged up and put to one side
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cb400a
Apr 11, 2021 15:24:26 GMT
Post by buster on Apr 11, 2021 15:24:26 GMT
onto the barrels, a light hone, just enough to clean em up, then a lot of pratting about scraping old gaskets off, fishing the o rings out and an initial sluice down with petrol then slugs cleaned (can you spot the difference between these and 400 SD?)
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cb400a
Apr 11, 2021 15:52:24 GMT
Post by buster on Apr 11, 2021 15:52:24 GMT
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Post by duffer on Apr 11, 2021 16:48:03 GMT
and finally, for today, I stripped the cylinder head out. I might have to empty those exhaust ports with a shovel What's it been running on, coal ?
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cb400a
Apr 11, 2021 17:33:18 GMT
Post by buster on Apr 11, 2021 17:33:18 GMT
and finally, for today, I stripped the cylinder head out. I might have to empty those exhaust ports with a shovel What's it been running on, coal ? oddly it seemed to run quite nicely before I stripped it. I reckon the balance chain had never been adjusted from new but it didnt sound bad also the guide and the cush rubbers seemed better than most. some of that. in the exhaust ports might be down to me filling the ports with petrol for half an hour before I stripped it
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Post by buster on Apr 17, 2021 15:59:19 GMT
picked up a few more bits and bobs from my carefully hoarded stash of spares. kickstert shaft is missing its square doofer but the automatic shaft might have one.
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cb400a
Apr 17, 2021 18:58:11 GMT
CTB likes this
Post by buster on Apr 17, 2021 18:58:11 GMT
so most of today was spent on the cylinder head. theres possibly a very good reason why those exhaust ports were so clarted up, the 400a uses a 250 spec cylinder head, that combined with the pistons and camshaft gives it the lower state of tune, I'll have to have a proper look at the carbs now and the cdi and the stator... so exhaust ports cleaned and polished (a bit) and valves lapped in and a good clean ready for painting (maybe) and reassembly
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Post by buster on Apr 18, 2021 10:52:02 GMT
so onto a quick run through the carbs. VB34's? jetted 72/105. the thought did cross my mind to put a proper 400 cylinder head on it but this brings about its own problems, it would need a new set of suitable carbs (inlets on mine are 250 size, I think) and the real hassle would be checking that theres clearance between valves and pistons (it costs you a head gasket to find out unless you have a secondhand one chucking about). otherwise the carbs are a familiar set up.
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cb400a
Apr 18, 2021 11:37:49 GMT
Post by CTB on Apr 18, 2021 11:37:49 GMT
Float seat looks a bit nasty 😬
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cb400a
Apr 18, 2021 14:27:54 GMT
Post by buster on Apr 18, 2021 14:27:54 GMT
Float seat looks a bit nasty 😬 they were, but not now, never known float pins as stiff, maybe never out before though I find that hard to believe
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