Honda C90 - Cam to crank timing

Honda C90 - Cam to crank timing

Timing The cam to crank timing is initially set when you assemble the engine. Timing refers to the regulation of the parts of a mechanism to ensure it works as designed. In this context it a reference to the mechanism by which the crank turns the camshaft and the valves in the engine are made...

Timing The cam to crank timing is initially set when you assemble the engine. Timing refers to the regulation of...

C90 Engine
Honda C90 - valve adjustment

Honda C90 - valve adjustment

Adjustment Here are the valve adjustment instructions taken from a CT90 workshop manual (the late 1970s CT90 and c90 z2 shared many engine components): The idea is to set the gap so that the feeler gauge just slides between the tappet adjustment screw and the top of the valve stem. As explained here the adjustment...

Adjustment Here are the valve adjustment instructions taken from a CT90 workshop manual (the late 1970s CT90 and c90 z2...

C90 Engine
Honda C90 - finding TDC on the compression stroke

Honda C90 - finding TDC on the compression stroke

As explained in this extract from a Honda manual, valve adjustment measurements must be taken at top dead centre (TDC) on the compression stroke.  This short article explains how to check your engine is in the right spot to measure the valve gap. valve adjustment instructions from the 1978 C90 Z2 owners manualTo understand Honda’...

As explained in this extract from a Honda manual, valve adjustment measurements must be taken at top dead centre (TDC)...

C90 Engine
Honda C90 - valve clearance

Honda C90 - valve clearance

Once you have the engine back together an important job is to adjust the valve clearance (sometimes called “valve lash”). The clearance you are adjusting is the gap between the “tappet” and the tip of the valve. Tappet is an Engineering term meaning: a moving part in a machine which transmits motion in a straight...

Once you have the engine back together an important job is to adjust the valve clearance (sometimes called “valve lash”...

C90 Engine
Honda C90 - valve seals

Honda C90 - valve seals

The valves are held in place by metal guides installed in the cylinder head and on some C90s (including the c90 z2) there is a synthetic rubber valve seal on top of the exhaust valve guide, as is shown in this diagram from the 1978 CT90 service manual: Honda tried a number of different valve...

The valves are held in place by metal guides installed in the cylinder head and on some C90s (including the...

C90 Engine
Honda C90 - valve lapping

Honda C90 - valve lapping

Doing an overhaul of the engine involves dismantling the cylinder head and inspecting the valves.  They will need to be cleaned of any accumulated oil and carbon, but do they also need lapping? Lapping If the valves are worn or pitted due to wear or because they have been poorly adjusted in the past it...

Doing an overhaul of the engine involves dismantling the cylinder head and inspecting the valves.  They will need to be...

C90 Engine
Honda C90 - valve inspection

Honda C90 - valve inspection

Here are a few posts on the topic of valve adjustment.  Happily, since the c90 is such a simple engine, it is a good place to learn about these automotive fundamentals.  Here goes! Disassembly Here are the cylinder head parts for the c90 z2.  As you can see the z2 has contact breaker points and...

Here are a few posts on the topic of valve adjustment.  Happily, since the c90 is such a simple engine,...

C90 Engine
Honda C90 - engine & hub paint

Honda C90 - engine & hub paint

I used VHT SP995 CAST Aluminium Engine Enamel Paint to paint the engine cases and wheel hubs.  The cases had been repainted once before so I couldn’t really tell if it is a good match or not ( perhaps a bit sparkly? ).  Apparently the original paint used by Honda was called Silver Cloud but I...

I used VHT SP995 CAST Aluminium Engine Enamel Paint to paint the engine cases and wheel hubs.  The cases had...

C90 Engine
Honda c90 z2 - introduction

Honda c90 z2 - introduction

Introduction Honda’s Super Cub step-through motorcycle is the most successful motor vehicle ever built and a staggering number – well over 100 million – have been sold. I was lucky enough to find a low mileage 1978 C90 for sale a few miles from where I live. It ran for about half a mile before conking...

Introduction Honda’s Super Cub step-through motorcycle is the most successful motor vehicle ever built and a staggering number – well...

C90 carburettor