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CB550K - engine rebuild (partial or full)

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Bryanj:
You have to drill and tap the centre of the plug as its a largish diameter thread, you could also make an adaptor instead

K2-K6:

--- Quote from: Erny on February 28, 2021, 04:09:38 PM ---Thanks

One more question - can I consider replacing vavlve seals w/o removing head? I guess it is doable but maybe difficult and special tool to support valves from bottom needed?

--- End quote ---

Good first hand experience from Charlie there. I've not changed any with head installed so just an irrational, perhaps, fear for me, but would leave them if you have no signs immediately of needing to change them.

If you've confirmed the valves aren't leaking and happy with that,  then caution in doing something that may just bend one even slightly (touching a piston crown with one edge) may be a more secure route.  And eventually you'll get them easily if you do further work.

Erny:
yes, surely it will be better to do it when head is off. Only motivation to replace them now is oil consumption - if after replacing seals oil consumtion will be reduced and only remaining weak place will be rings/pistons.
I assume seals will be hard after 46 years so not sealing properly I guess

But I'm only investigating now what are options/way to do. If too risky/complicated or costly, I'll let it be

K2-K6:
Certainly I think Charlie's first hand experience out weighs my view, so doesn't appear a big risk.

But through observation of an engine showing oil use I generally seperate as, smoking under acceleration consistently then its normally rings,  with longer run (downhill) with throttle closed,  then emitting smoke just when you open the throttle (single cloud) is ordinarily inlet valve guides as it sucks oil down the valve stems (high vacuum in inlet tract) to be burnt just as you open the carbs again.

Good idea to make a list of concerns that you can then work through later.

Charlie J:
I changed the valve oil seals without removing the head as I was hoping for a quick fix for my smoking engine. Unfortunately, it didn't fix the problem and I ended up having a rebore, new pistons and rings and a whole list of other items whilst I was at it, resulting in an almost total rebuild!

Charlie

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