Honda Dream C77 (C78)

[petertohen]

Hi all, First time poster here.

I've recently acquired a C77 (C78) in Perth, Australia that I am in the process of recommissioning. The previous owner was not mechanically inclined and as far as I've been able to ascertain never had the bike running.

Aside from some obvious wiring gremlins and a few missing bits and pieces the bike seems to be in fairly good order, however this evening I removed the spark plugs to undertake a compression test to find that they are different sizes!

The left side housed a 12mm, short reach NGK (it was an NGK D8HA). The right side housed a larger (14mm) diameter plug (B7HS), of the same thread reach.

Presumably a previous owner cross-threaded a plug, then had the head machined to the next sized plug.

I've not heard of this solution before. Has anyone here had experience with this sort of thing? Is it a reasonbable solution? I ended up doing a compression test and both sides produced similar results. Should I be worried?
https://www.amazon.com/Honda-Dream-CS72 ... B0768Z9QQK
Cheers,

[Geoff Hastings]

Hi there, the plug thread should be, as you guessed, the 12 mm. You could just leave it, or there is a 14mm to 12mm adaptor on the market so you can keep both plugs the same size. Another solution, if you are going to strip the engine, is get the head welded up and re machined back to original or final solution buy another head.