Honda Foreman

I have a newer Honda Foreman in the shop today with a shifting problem.  It was hard to change gears, and impossible to get into neutral.  The transmission on this machine, like almost every ATV, is part of the engine.  In order to do any transmission work you need to remove the engine from the frame.  That takes 2 to 3 hours on this machine.

Once I had the engine on the workbench I pulled the side cover off and removed the clutches to expose the shift mechanism. 

 Part of the escapement mechanism that that turns the shift drum was broken.  This machine was sunk under water last winter.  I suspect that this piece broke when someone tried to shift the machine with the crankcase full of ice.  This second photo show the broken part and another used part that I had left over from a Honda 420 rebuild project.  It appears that Honda uses the same shift linkage on the 500 and 420.

This last photo shows the shift mechanism put back together. There are a lot of springs, spacers, and little parts to keep track of.  Now I need a few more hours to put the engine back in the frame and try it out.

C.O.

Honda Foreman

2008 Honda Foreman TRX 500 FM

This machine is a great example of Honda engineering.  It is nothing fancy or high performance, but well thought out and durable.  The engine is a basic single cylinder four stroke motor with push rod actuated overhead valves.  It is air/oil cooled with an electric fan.

This is a standard ATV here in the village. These machines will last forever if you keep oil in them.  Unfortunately people seem to have a habit of running them out of oil.  The normal engine disaster starts just after someone changes the oil.  They either strip the threads on the drain plug and it falls out a few days later or they put the oil filter in backwards.

The stripped threads are definitely operator error, but the upside down oil filter is an engineering mistake by Honda.  The filter is a cartridge type with a hole on one end and a spring that pushes on the other end.  If it is installed backwards the hole for the oil to flow through is blocked off and the engine does not get any oil.   I have seen these problems many times.

The lack of oil typically leads to an overheated piston and cylinder.  If you run it long enough like this the piston breaks.  The rod and crank have roller bearings, so they normally survive fine.  Being a push rod motor, the cam is low in the block and it normally has enough oil to survive.

I'm not sure what is wrong with this particular one yet, it smokes pretty bad out the exhaust, uses a lot of oil, and sounds a little "rattly", but it still runs ok.   I'll pull the top off tomorrow and see what it looks like inside.

C.O.