Timing Marks

Do the timing marks inside the engine have to be 100 % on the money accurate for the engine to fire up and run?

I have a 77 kz750 twin B2. I swapped the crankshaft, flywheel, stator, R / R, and pickup coil from an 82 M1 Csr. The engine will fire up and run for about 2 sec and it sounds good not lope-y meaning it doesn't sound outta time but then I'm doing calisthenics for 2min till it tries to fire up again.

I really don't wanna have to take the engine apart again I hope it's some thing easy like the carbs being outta sync but since I never rebuilt an engine before I'm worried. Any help?

here is a pic of my twin.

never mind about the picture but I will tell you she is beautiful.

Good Fortune!

Make sure you have fuel getting to the carbs. A pinched fuel line, etc. can cause the problem you describe. You can check the bowls to ensure they are filling properly. Ed

Hackworth wrote: Do the timing marks inside the engine have to be 100 % on the money accurate for the engine to fire up and run?

I have a 77 kz750 twin B2. I swapped the crankshaft, flywheel, stator, R / R, and pickup coil from an 82 M1 Csr. The engine will fire up and run for about 2 sec and it sounds good not lope-y meaning it doesn't sound outta time but then I'm doing calisthenics for 2min till it tries to fire up again.

IMHO, it would not be able to run good with a serious timing issue. This sounds more like a fuel issue, but I would also caution: if it's the original coil, it is probably weak and flaky.

Do you have the stock air box on?

For fuel problems:

make sure your gas cap is venting so it isn't vapor locking for gas.

Clean the tank thoroughly, clean the petcock assembly.

Install inline fuel filters.

Clean carbs throroughly. Install #50 pilot jets, they run better than the stock 45s.

Bench adjust the throttle butterflys to sync them.

Don't bother trying to bench set fuel levels, it won't work. Use the clear tube. Best setting for fuel level is 5mm below lower edge of upper carb body.

Check the diaphragms for any holes or slits.

IMPORTANT: make sure your timing advancer is working correctly, if not it will make the engine terribly hard to start.