Exhaust header heat

[tom1104]

Hello all,
Is it normal for the CB77 exhaust headers to be far to hot to touch after running for about 10 seconds?
I'm wondering if there may be some kind of air leak causing the engine to get very hot, the idle gradually gets higher. The previous owner did a top end rebuild and I'm now wondering if it was done properly, there's also a small amount of oil coming from the front of the cylinder head around the gasket and a slight oily residue in the right side exhaust
Thanks

[Tim Allman]

The first question is easy to answer. Yes, the exhaust temperature will be in the 200 to 400℃ so it won't take much time to heat the headers.

The oil leak is one that I'm also dealing with now. Most likely the cast iron cylinders are a bit high so the O-rings that sit inside the holes for the left and right studs are not sealing well. Or perhaps the head is not flat or something else is preventing the head and cylinder block from coming together properly. You can have great compression but still have the oil leak. Before taking it apart I would re-torque the head nuts. That might seal things up.

I don't know what to say about the other problems.

[tom1104]

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.

[Tim Allman]

Yes. These nuts have unusually high domes. They have their own part number, 90281-259-000. I've seen them for sale before but I don't know who's selling them at the moment. You might try a Honda dealer first as I have found that some parts are still in the catalogue, especially the more generic ones.

[tom1104]

Thanks again Tim,
I'll try and get hold of some of those, I went over all the basics again and now the bike seems to be running well! So I don't think there is actually an air leak after all. The only thing I have now is popping during idle coming from the left exhaust

[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.

Correct set of four domed nuts currently on eBay: https://www.ebay.com/itm/264388695742?

[tom1104]

Thanks for the link but I'm located in the UK and it looks like they don't have the option to ship overseas