SOHC.co.uk Forums > CB350/400

400/4 no spark

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K2-K6:
Same as Julie's view,  something distinctly odd about that as they should all be the same.

In the past and when they where contemporary,  a friend with engineering shop could leave a milling machine setup specifically for these engines so numerous did they encounter problems with plugs that hadn't been changed on centre two cylinders and seized into the head.

It's quite likely that the centre two have been worked on to correct plugs that corroded in there,  quite what form you'd need to establish. It's not a show stopper but you need to evaluate to see what you've got.

Could someone have chased the two plugs down with die to get them fitted?  Do they spark ok to try it without having to immediately replace those two odd plugs?

2 for the soul:
Well that definitely makes sense if someone's had to do some work to get seized plugs out. Odd that the DR8 plugs seem to fit.

I'm pretty sure they spark but I'll have to wait till next week to double check - if they do spark is it a disastrous idea to run using different spark plugs as long as they fit?

Thanks

K2-K6:
They'll work ok,  we talk about it on here as regarding R versus non R plugs for which there is a consideration as to their effects. I'd certainly deal with that later if you want to run it now.

You'll be able to ride and assess it ok with the mix (although though technically incorrect) they'll not cause any damage, then work out a strategy to get to where you can sort it.  It's no sweat at the moment if they spark ok.

If you can work out what you need to do to get it sorted it's probably better not to get something jammed in there right now as it could snooker you for easiest fix.

Thread is 12mm times 1.25 pitch for a tap to run through the existing setup to chase out the tight ones,  so could be a mid term plan to sort it.  Failing that,  more detailed removal of head to assess may be another course to take,  sounds drastic but it's fairly routine on these to give a concise view of condition and action required.

2 for the soul:
Brilliant! Thanks for the insight. My biggest worry was keeping them both and doing damage. I’d seen a post discussing the R and it sounded like it wasn’t a good idea but I couldn’t figure out why, but if it’s not going to stop me running it for now it’s something I can fix over the winter then that’s great!

Thank you for the help!  :)

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