Help! Any ideas........all (clean) suggestions appreciated.

[SIImad]

My SIIA 4cyl conked out the other day while I was driving it Kms from nowhere (a very common location to breakdown!).

At first I thought it was the usual drama I have been having with the carby and it had just flooded, so I had a passer by who stopped to see if I needed help turn over the motor while I held my hand over the carby in order to clear the flooding. Instead of the carburettor sucking my hand downwards it blew upwards and there was no petrol with it just air, and the engine would not run. I repeated this several times and got the same result a positive pressure instead of a negative one from the accursed Solex! Eventually, I had to call the RACV and get the thing towed 60kms home. The mechanic came up with all different theories, which included a stuck exhaust valve, a broken crankshaft, and/or timing chain, and (as usual) said it would cost "big bucks!" to fix, I believe him, truly I do!:p.

I removed the rocker cover and hand cranked the motor, all of the valves and tappets operate, which eliminates the timing chain, broken crankshaft and the stuck exhaust valve theory. I am suspecting that it may be the diaphragm or jets in the Solex carby. Any other ideas and suggestions would be greatly appreciated, at this moment it has got me stumped.

AJ.

[harry]

Well the stuck ex valve isn't going to pressurise the inlet manifold, but a stuck bent inlet valve will, or a dropped inlet seat if your engine has them, do a compression check and you should get an idea

[Blknight.aus]

skip the compression check to begin with.

whip out the plugs and using an adaptor or rubber bunged air duster blow compressed air into the spark plug holes with the valve adjusters backed right off. (better yet, remove the rockers completely)

if you get air out the inlet or exhaust you have problems.

and yes, a stuck exhaust valve will allow air back through the inlet manifold. just not as much as a stuck inlet valve (you will have 2 exhaust valves open, one will be trying to pump air out of the cylinder and down the exhaust the other will be trying to stay closed because its cylinder is on its intake stroke. its a lot worse if the engine is running)