I recently had my barrels off the engine aswell as the engine out of the bike completely, not fun!

Well i replaced my piston rings as they were damaged although the cylinder bore and piston are fine, infact as far as i could tell everything was so i reassembled it and reinstalled.

Now after filling it up with slightly less than full worth of oil and put all the other bits on i cant get it to start.

There's a few things that are appearing to be problems.

1) The engine turns over fine although i don't think theres any fuel getting to the cylinder which leads me to my next problem.

2) I've now managed to lose two vaccuum caps after they shot off the top of the carb, obviously the cylinder compression is coming back out through the carb some how and popping the vaccuum cap off (they get some height!). Considering i've had the inlet and exhaust timing thingies out could this suggest the inlet is not opening in time and when it finally does the built up pressure from the cylinder is going back into the carb?

I did honestly believe i'd timed everything right after following the manual instructions exactly as stated!

3) I'm getting a spark but it's pathetic and barely visable on both cylinders, the batteries fine and holding a good charge but after having several wires off the engine while taking it out perhaps i havent wired something up properly, i don't believe it's the coils or plug caps as these were fine before the rebuild?

I had concerns as i couldnt remember where the negative "earth" cable attatched to so i've connected it to the RHS engine casing.

Any help on any of the problems?

If it involves dropping the engine out again i might just sell the bike!

well, you've pointed to ignition, fuel and questionable cam timing (i think).

the cam timing is easy enough to check with the valve cover off.

fuel delivery is easy enough to check by opening the float bowl drains.

spark is easy enough to check if you have a buddy with another gs to borrow coils from. make sure your battery is in FANTASTIC condition. starting the bike puts a huge load on the battery, if it's underperforming, spark will suck.

replace those vacuum caps !

2 cents

Thanks, how would i go about checking the timing?