i have a gsxr gk76a that im having nothing but problems with. ive replaced the engine in it as a favour for a friend as the old one was blown big time. ive installed a second hand engine but when i spin it over it sounds like its going to start and then fires the vacuum cover off the top of the carb on cylinder one.
obviously this is because of a build up of pressure in the carb when there should be a vacuum. so i have checked:

valves
timing
carbs
all seals around the valves
re lapped all valves
shims
ive checked so much ive forgotten half of it.

none of this has made any difference at all. has anyone had this problem before that can help me im spent on it and if it doesnt fire soon it will probably be on fire its doing my head in.

PLEASE HELP ME!!!!!!!

cheers in advance

Ollie

Sounds like the valves are not sealing or the cam timing is wrong.

valves appear sealed and have been correctly lapped in there was no signs on the valves of leaking gasses. no valves were bent.
i have triple checked the timing and all appears fine.

ignition coils wired back to front? causing a backfire through the carbs, blowing the vacuum rubbers off?

CHR15 wrote:ignition coils wired back to front? causing a backfire through the carbs, blowing the vacuum rubbers off?

this was my problem, but it was the wires from behind the clocks that were wrong, swapped over and worked perfect

has anyone got a photo of how these should be wired up and what ht goes to where.

Im sure there is a wiring diagram in the manual downloads section.
HT wire 1/4 and 2/3.