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400-4 Engine rebuilt

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DayvW:
Hi,

With the invaluable help of members of this forum I have completely stripped and rebuilt my 1976 400-4 engine - and she lives again! It all started with some weird grinding noises (not to mention cam chain chatter and primary chain slap) and the urge to remove all the horrible paint/lacquer that was peeling and  generally looking a right mess.  So she was stripped right down (and soda blasted) and the primary chain replaced (along with the cushion rubbers as advised on this forum) plus the cam chain was replaced together with the adjuster arm (a new one from DS as mine was completely seized and worn away),plus the slippers.  All the engine seals were replaced, but the bearing shells all looked fine so they have stayed.  At the top end I replaced the piston rings (all were well outside tolerances despite being 1mm o/s rings - so clearly at least one rebore in its time (indeed it was clear that the barrels have been off - but I dont think the bottom end has been touched in its 38 years). I also replaced all the valves as virtually all were hammered - literally.  They looked as if they had been ground, but I suspect in doing this the hardened 'crust' have been removed meaning that the tappets have been slowly wearing into them (I replaced the tappets too) -so they looked pitted.  And valve seals of course.  Something I spotted when putting the rockers back in (and not mentioned in the original workshop manual that I am fortunate to have) was where the springs that keep the rockers apart should go.  If you get them wrong the tappets dont quite line up properly with the valves - I noticed that the way around that they had been mean that was indeed the case and I wonder whether that too lead to undue hammering of the valve stems (perhaps an expert can comment on that?).  I just looked through my photos of the strip - and annoyingly didnt take a pic so cant show you which way around I have them now!  I have just balanced the carbs (I did also strip the carbs and cleaned them, one float was 'sticky' due to the hinge pin being slightly bent and this meant I used to pour fuel over the floor if I forgot to switch off the fuel tap - not any more!) - and she's running sweet as a nut.  So - ready, I think, for an MOT next week.  I have to say I am well chuffed having never done more engine fettling than replace a GT380 piston many, many years ago when I inadvertently holed it after fitting expansion pipes without re-jetting!).  I have absolutely loved it.  Yes there have been frustrating moments - but I've said before (and I wont stop saying it -so tough!) that this forum has helped me no end.  Its so good to look at (and listen to) a sweetly running engine and to think I have stripped it right down, replaced stuff that needs replacing, rebuilt it .. and it works!  I plan to do more over the years - but this one will always be the special one.  And to celebrate I attach a gratuitous shot of said bike as she is now and a few of the many, many in progress shots.

hairygit:
Well done on diving in there, glad it all works again sweetly, and long may it continue to do so (Change the oil and filter regularly and no reason it shouldn't) ;D

DayvW:
Many thanks  ;D

UK Pete:
Thats great work Dayvw, i bet your well chuffed,
pete

mickwinf:
well done mate, I am nearly there with my 500!

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