Engine tickover

Post by **wanderinstar** » Fri Jun 23, 2006 7:44 pm

When I take the rocker cover cap off, the engine speeds up significantly and runs smoother. Why is this? Breather on tappet chest cover IS connected to carb.
Ian.

Post by **Willie** » Fri Jun 23, 2006 7:52 pm

This is because you are allowing unrestricted fresh air to enter the Carb
which will weaken the mixture which usually speeds up the tickover. It may
indicate that you are running a bit too rich which should be easy to check
via the lifting pin.

Post by **wanderinstar** » Fri Jun 23, 2006 7:56 pm

Willie,
I dont understand this. How can me taking oil filler cap off be letting fresh air into carb. Also its an HIF 44 so it doesn't have a lift pin. I dont think.
Ian.

Post by **Willie** » Fri Jun 23, 2006 8:00 pm

You say that your engine breather pipe enters the Carb (not the air filter)
Therefore it is sucking crankcase fumes in to the Carb. If you remove the oil filler cap which is the INLET for air to enter your type of engine(with a wire
filter in the cap) then you are allowing more fresh air to enter the Carb more
easily. More air equals a weaker mixture which means an increase in tickover speed. I know nothing about the HIF44 carbs.

Post by **bmcecosse** » Fri Jun 23, 2006 11:41 pm

Willie has it in one ! It basically means your engine is in good condition - otherwise taking the cap off would result in fume pouring out - you have air going in, through the block - and then into the carb ! My HIF 44 has a lift pin. But you can just use a thin screwdriver in the mouth of the carb to lift the piston by 1/8" - same effect.