aprilia sr50 wont start

bit of a break through went to kick it over this morning and it started not reving or idling very well but coolant is coming out of the cylinder head so could this mean loss of compression and could this be the cause

 

are you talking about a leak from the gasket area between head and cylinder?

if so it's either gasket breakdown, head is warped, or you didn't torque the head down sufficently or in stages diagonally.

The only other things is old gasket left in place, or the top of the cylinder has warped.

some of those you can discount as you rebuilt the engine.

Of course if the combustion gases are leaking to the cooling system, then your compression is going to be down and it's possible coolant will enter the engine. Sometimes the breech is so small that it acts as a non-return valve allowing gas one way, but stopping the coolant re-entering as a molecule of gas is smaller than a molecule of coolant.

Were the coolant hoses bulging at all? Was the temp gauge rising quicker than normal.

bottom line is to take the head off, and inspect the components.

 

yeah the big gasket that goes all the way round the top and its just leaking the tinyest bit and my bike wont fire up today so i wouldnt be able to say about the temp gauge and no old gasket is there but it was a circle gasket where as my engine looks like a house shape so i think the gasket is wrong just wondering out of interest could the starter relay stop my bike going cos someone said so and the autochoke cables have snapped from erosion so could this stop it starting??? still waiting to but cdi/coil , voltage regulator and NGK HT Lead found them cheap so gunna put them on and eliminate them of my list