While the machining and restoration of your cylinders might be done when they arrive back from the Common Motor Machining Service, the work is not. Rebuilding the engine from the ground up requires careful consideration and attention to ensure things are put back together properly. If in doubt, we highly recommend having a professional with experience rebuilding these vintage Honda motorcycle engines perform your engine rebuild.
If you are rebuilding your engine at home, we have put together a few tips and tricks for the important jobs that need to be done before the cylinder and pistons are installed onto your motorcycle. These instructions are intended to be used alongside the factory Honda service manuals linked below. Be sure to download and read the Honda service manual engine sections throughly before beginning any rebuild on your motorcycle.
Thoroughly Wash Cylinders
After being serviced, the cylinders are coated with a rust preventative. This must be washed away before assembling the engine. Wash the entire cylinder jug in hot soapy water. Dish soap or a water based detergent is preferred. When the cylinder is totally clean, you should be able to wipe the cylinder walls with a clean rag and there shouldn’t be any gray residue on the rag.
Gap Piston Rings
The pistons are matched to a specific cylinder, but the piston rings have not had the gap checked. Follow this procedure detailed in our video according to your Honda factory service manual as these values differ between engine families.
Install Base O-Rings
During service, the cylinder base o-rings have been removed. Be sure to properly install new o-rings in the groove at the base of each cylinder. Carefully push the o-ring into the groove until it is properly seated with either your fingers or a dull object that will not puncture the o-ring. These o-rings are included in our Overhaul Gasket Kit for each engine.
Check Head Gasket/Copper Coat
Be sure to check the fitment of the head gasket before engine assembly. Sometimes the gasket may not lay entirely flat, this can be corrected by trimming the gasket around the knock pins. We also recommend spraying the head gasket with a copper coat sealant, this will help fill in any imperfections on either gasket surface and help prevent any oil from leaking past the gasket.
Installing Piston Rings
Piston rings must be installed carefully and in a specific way so they do not break or leak oil into the combustion chamber. Modern 3 piece oil rings make this a lot easier but breaking a piston ring during installation is still easy to do. The piston rings need to be oriented with the correct side facing up, in the correct order, and with their end gaps facing the correct way. With a modern 3 piece oil ring, the first and middle piston ring end gaps should face 180 degrees away from each other. Each piece of the 3 piece oil ring should face 120 degrees away from each other.
Installing Pistons
Each cylinder has been machined to match a specific piston. Each piston will be marked either L or R on the twin cylinder engines for left and right. The orientation of the cylinders is from the rider’s perspective when sitting on the motorcycle. For four cylinder engines, they will be marked 1-4. The orientation will be from the same perspective, with the #1 cylinder being on the outer left side of the engine. These markings won’t affect performance, but if you would like to remove them after installation use acetone to wipe them off.
Installing Cylinder Jugs
Installing the cylinder jugs is the last piece of the puzzle before you move on to the head and the remainder of the top end assembly. Many of the cylinder base gaskets and head gaskets are known for leaking from the oil passages on these motorcycles. We recommend adding extra insurance using Hondabond 4 or equivalent gasket makers around the oil passages on the upper crankcase and bottom of the cylinder. Cam chain tensioner lower components will also get installed with the cylinders. Be sure to refer to the Honda factory service manual for the specific model of motorcycle you are working on for these exact instructions.
Follow the Factory Service Manual (FSM)
The Honda factory service manual for your specific motorcycle will be the step by step guide for reassembling your engine correctly. You can find a PDF version available on our website below.
Honda CB175, CL175, SL175 / CB200, CL200 Factory Service Manuals
Honda CB350 | CL350 | SL350 Factory Service Manuals
Honda CB360 | CL360 | CJ360 Factory Service Manuals
Honda CB450 / CL450 / CB500T Factory Service Manuals
Honda CB500 and CB550 4-Cylinder Factory Service Manuals