SOHC.co.uk Forums > CB350/400

Engine Strip - I'm nervous

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Bryanj:
Yes it is necessary to replace primary chain and cush rubbers

PatM:
Trigger and Julie know their stuff as they have done all this before.
Just to pick up on one of your points which I think i can answer-

(4c) The oil pick up filter has metal pieces in it. It was also covered in thick gunge almost like gearbox oil.

When I rebuilt mine 9 years ago . I bought it as a sorry-state non-runner. Id not had one since the early 90's.
I popped off the sump and found the same as you-it was aluminium gunk and bits all over the strainer, so I cleared it off and promptly put it all back together without to much consideration as to where it has come from. I was hoping it was general wear and or sloppy oil-changes.

I was chatting on here to Julie about cam-chain adjustment as I went to 'adjust' mine and undoing the adjuster made little difference-even though its a stainless steel bolt and nut. The penny dropped-my lower cam-chain horse-shoe has seized.
 Now, Julie told me Id have to strip the motor to replace it-which is correct-but I read about this somewhere and although its not a permanent fix (Julie said its a bodge..) You can insert a long thin drift down the throat of the chamber-accessed via the large cap thats above the adjuster- and 'tap' the drift. This, in my case moved the lower horse-shoe and shut the cam-chain up. The metal on the strainer was non-metallic and caused by the chain rubbing/eroding the throat of the chamber.
Im actually and engineer!-but I saw little benefit at the time stripping the whole motor-I retire in a few years, have too many other bikes to maintain and cars...Ill save all that for then-its not as if the 400/4 gets much use-used in thrice in 2019- and I know what the cam-chain sounds like when its loose!
I also plan to do the head/valves but if Im going to remove the motor and start dismantling it-Ill do it once!
Ive rebuilt these motors before back in the early 80's and I know how easy bolts strip or heads snap off- my bikes running perfectly well and Im not into causing myself a load of grief, neither have I the spare cash to instantly resolve it! Back in the 80's you can pick up a running 400 motor for £50- no problem- the breakers were full of them in London area.

waffey:
Thanks PatM,

i'm hoping my 'bits' in the strainer are the same as yours. Hopefully i'll have the crank case split this weekend.

I'll post some more pictures then. The frame is booked in for the 10

Bryanj:
Considering you had broken rings i would not even bother measuring but buy oversize and rebore, chances are that the broken rings have worn the ring grooves in the pistons.

Trigger:
As Bryan has already said, not worth the trouble with the pistons , a engineering shop can charge around £45 just to measure up and then tell you that you then need a rebore. You can get a good oversize set from Japan for about £110 including post. Get a good engineer to rebore at a piston to bore clearance of one thou , if anyone tells you that this is too tight, walk away as, they don't know what they are doing.

If the sump pan is leaking from the drain bolt, look for a good secondhand one that has not been welded. Never torque a sump bolt more than 20 ftlb on these old girls or they will crack the pan  ;)

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