Oil at spark plugs

[MNArie]

If anyone is looking for a permanent solution to this oil seepage around the spark plugs for Honda 250 and 305 CA72/CA77, CB72/CB77, CL72/CL77 models, I have an easy to install solution to this very old problem. Honda Service Bulletin 68 gave no definitive fix to this problem and I will supply you with a copy of the ORIGINAL Honda service letter. Simple installation of parts with detailed instructions and assembly photos are supplied - no major engine disassembly is required to do this fix. Please contact me for questions you may have. You won't be disappointed and this solution and it quickly will save your beautifully restored cylinder head as no more engine oil will be baked onto the fins and exhaust header clamps.Testimonials from satisfied users can be supplied upon request. email: aboers@comcast.net or call or text 612-382-5116.

[Nick]

Slight thread drift, but the Yamaha XS650 also used an iron skull cast into the aluminum head, a design they borrowed from the Toyota T-2000 sports car (which Yamaha engineers helped design).

[DJM]

Those of us who's CB72s or 77s are plagued with oil leakage near the spark plugs might be interested in my recent experiences with this annoying issue.

Having owned CB77s for longer than I really care to remember I've known about this issue for years. Some engines seem to leak a bit of oil in this area, most don't. Some leak a lot!

American Honda published a Service Bulletin about it back in April 1966 so obviously the problem was recognised even when the bikes were new.

Since retiring a few years ago I've built myself both a CL77 and later a CB77 to go with it.

Both engines were rebuilt with new cylinder liners and in both cases the machinist, as was his usual practice, machined the top of the new liners dead level with the top of the cylinder block.
At this point I must state that this guy has been working on Honda engines for over fifty years and I would always accept his opinions and advice and experience as being vastly superior to my own.

However, sadly, both of my newly built engines had minor oil leaks around spark plugs, not much but something I found intensely annoying as Hondas, even back in the 1960s, weren't supposed to leak oil!

Reading the Honda Bulletin on this subject I was inclined to blame the fitting of the cylinder liners but wasn't really convinced that an engine rebuild to adjust the fit of the liners would affect a cure so I procrastinated and did nothing other than clean the engines regularly.

Earlier this year I spotted a reference on this list to a 'repair kit' offered by Arie Boers and after some thought decided to give them a try.

Deciding factors were that the kits were simple to fit and could be installed without any dismantling of the engine, in addition the kits cost no more than a gasket set which I would have needed anyway if I had embarked on an engine rebuild, the results of which were by no means certain.

I've now fitted the kits to both engines and really pleased with the outcomes; after 1500 miles (CL77) and 600 miles (CB77) both engines are completely clean and dry in the area surrounding the spark plug so have entirely vindicated by decision.

Based on my own experiences I can recommend these kits to anyone with a similar problem, the only caution I would add is that TOTAL cleaning of the area around the before fitting the kits is essential, as in most things, proper preparation is key to a successful job!

I have no connection with Arie Boers other than as a (very) satisfied customer.