Exhaust header heat

[deuce_7]

The seller might be willing to change shipping options for you.

[deuce_7]

Thanks Tim,
One thing I have noticed when investigating is that the 4 inner cylinder head dome nuts are quite short looking. I did read somewhere that the CB77 cylinder head nuts have a specific inner depth, could it be that the nuts are bottoming on the studs and not torquing down correctly.

Did some measuring this weekend; the inner depth dimension of the correct 90281-259-000 dome nut ((called "NUT, CAP, 8 M/M" in Honda parts list) is: 15mm. The overall height of the nut is 16mm, which means the top dome has a thin 1mm wall.

[Tim Allman]

The only studs which truly require acorn nuts are the two front outer ones with the copper washers. It would be better to use ordinary nuts for the others to ensure that they are properly torqued. That is, that the studs not top out on the insides of the nuts.

[deuce_7]

The only studs which truly require acorn nuts are the two front outer ones with the copper washers. It would be better to use ordinary nuts for the others to ensure that they are properly torqued. That is, that the studs not top out on the insides of the nuts.

Concur.

The official Honda CB77 parts list shows eight acorn 8mm nuts and 8 copper washers. To the expert eye, standard hex head nuts on a 305 might look a bit odd and not to spec. Although in 1967, apparently Honda issued new bikes with standard hex head nuts on the forward center studs (as mentioned elsewhere in Honda 305.com Forum).

[Tim Allman]

I the parts book I have early bikes (before CB77E-1005895) used all copper washers while the late ones used four although the diagram doesn't show where. The reason I said that two would be enough is that only two stud holes double as oil passages. If you look at the gaskets, the other studs should be dry and therefore not need sealing.

I suggested that ordinary nuts would be better than acorns that are too small simply because I thought you just wanted to get the bike running. They would indeed look a bit funny to those of us who know these bikes.

[tom1104]

Thanks Tim,
I actually sourced some deep acorn nuts from a shop here in the UK, they have the same inner depth of 15mm, only difference is they are 13 instead of 14. But they seem to have done the job
Tom

[Tim Allman]

The switch from the pre-1970 JIS to what is essentially ISO is a constant headache. No one but one of us obscessed Cx77/72 will notice.