Its been about 6 months since I purchased a non-running 1981 CB900 Custom with intentions of building a cafe racer, even bought a blackhawk swing arm and SV1000 rear adjustable monoshock. Some reading this probably just cringed as I came to learn the obvious uniqueness of the CB Custom line of bikes. The CB900 Custom unlike similar shafty bikes has what I would call a transfer case that delivers power from the left side of the bike to a shaft on the right side. See the CB is an inline 4 cyl that uses a GL flat 4 cyl (goldwing) final drive. Honda developed essentially a transfer case with hi/lo to marry the mismatched pair in a slightly modified (streched) frame. Its not ideal for a Cafe racer but have since decided to build a bobber out of it. I recently bought a 900F chain driven beater for my cafe project.
You can see the oil blow by on the #1 Cyl
First, whats wrong. I was told it was running when it was parked but while driving home from work it started running very rough. First had to put a new battery in and removed the gas tank that was rusty and had 8 year old varnish (gas) in it. I didn't want to run the engine if it could fire for fear of making what ever problem there was worse. The new battery brought it back to life and luckily the ignition switch and starter worked great. Pulled the plugs and did a preliminary compression test and quickly found the root of the problem. Cyl #1 was dead with zero compression. I removed the valve cover and had very good wear lines on the cam and good movement so not a stuck valve. I decided at this point it was time to pull the engine.
