Scooterboy
CB750 New member
Hi there, does anyone know if a cbx750 engine is a direct replacement for the standard motor in a cb750 nighthawk (1995) I've no compression on one cylinder and can't find a CB engine anywhere in the uk
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Cbx engine
- Thread starter Scooterboy
- Start date
amc49
CB750 Guru
What if you've only burned a valve or blown a single cylinder on head gasket?
Can't say it won't but one engine ran through 1988 and the other '91 and up. Expect some changes, Honda NEVER leaves things alone. I question if the earlier motor has the cylinders a degree or two more upright, but just could be how it fits the frame. The CBX has a shallow sump, the frame carries part of the engine oil, if yours doesn't do that could be issues there from lack of oil. Maybe different sumps interchange? The engines do look pretty close.
Can't say it won't but one engine ran through 1988 and the other '91 and up. Expect some changes, Honda NEVER leaves things alone. I question if the earlier motor has the cylinders a degree or two more upright, but just could be how it fits the frame. The CBX has a shallow sump, the frame carries part of the engine oil, if yours doesn't do that could be issues there from lack of oil. Maybe different sumps interchange? The engines do look pretty close.
Scooterboy
CB750 New member
Everyone I've spoken too says it's not worth messing with just buy another engine as its so time consuming to work on, I'm going to take the head off and see what the damage is, it will be my 1st 4stroke engine strip, it can't be much more complicated than a single cylinder air cooled two stroke surely,,,,��
amc49
CB750 Guru
Famous last words.
Uh, two strokes have no cams and how one gets into trouble................LOTS more parts to deal with there.
Not saying it can't be done at all but much more caution needed. Two strokes are locked into all engine event timings, four you have to set most of them, double cams even more confusing. Have a service manual at hand or don't try it.
To begin with, mark or match ALL parts when you remove them, you cannot mix cylinder for cylinder parts. On a twin cam 16V four that will be 16 separate freezer bags of assembly parts for each valve location if you pull the entire head down, you absolutely cannot mix those up. Same with cam caps that hold cams down, timing chain needs to go back in turning same direction it came out going. Every part reused has to go back where it came from exactly.
Mess up removing valves and you just messed up the head, it will need valvework then, each valve has mated to its' seat.
You cannot move the crank at all without considering where the valves are at all times. How most mistakes are done, bent valves while turning engine over to work on something else. The small valves bend so easy you often never notice it until trying to start the engine.
Uh, two strokes have no cams and how one gets into trouble................LOTS more parts to deal with there.
Not saying it can't be done at all but much more caution needed. Two strokes are locked into all engine event timings, four you have to set most of them, double cams even more confusing. Have a service manual at hand or don't try it.
To begin with, mark or match ALL parts when you remove them, you cannot mix cylinder for cylinder parts. On a twin cam 16V four that will be 16 separate freezer bags of assembly parts for each valve location if you pull the entire head down, you absolutely cannot mix those up. Same with cam caps that hold cams down, timing chain needs to go back in turning same direction it came out going. Every part reused has to go back where it came from exactly.
Mess up removing valves and you just messed up the head, it will need valvework then, each valve has mated to its' seat.
You cannot move the crank at all without considering where the valves are at all times. How most mistakes are done, bent valves while turning engine over to work on something else. The small valves bend so easy you often never notice it until trying to start the engine.
