TOPIC:

I have a fresh bore new pistons and a fresh valve job,with no carbs or exhaust on the motor,I can hear and feel air coming out of the exhaust ports when I flow air through the sparkplug holes with each piston is at TDC,is this normal,should I get some air,or should it be totally sealed?

have you adjusted the valves;)

What TDC? On the exhaust stroke or on the compression stroke? I'm assuming you do have the cams installed.

yes,valves are adjusted,tdc on the compression stroke

If you have valve clearance, recheck that the exhaust cam is installed correctly. If it is, the head will have to come off and the valves lapped to see if they will seat. Make sure they aren't bent, and if they won't lap in, cut the seats slightly and lapp them in.

Might want to double-check camshaft timing. If incorrect, hope this didn't bend any valve stems.

I am thinking that only two exhaust valves will be closed at TDC. The other two will be open. Leave your valve cover off. Then put some air into the plug hole and check the two that are closed then roll the engine over 360 degrees. Hopefully you set you cam timing properly... the chain needs to be wiggled and pulled a the front of the engine before installing the exhaust cam else it will be bunch on the sprocket on the crank.

Post edited by: wiredgeorge, at: 2006/12/22 07:59

When you have two pistons at TDC (1&4 or 2&3), one piston is at TDC on the compression stroke (both valves closed), and one piston will be at TDC on the exhaust stroke (exhaust valve closing and intake opening, both open a little, that's called overlap).