Motorcycle Repair: 1975 GT 750, GT750

Question
Can you help me and my mechanic friend ?  my bike is at his shop and he is concerned about leaning bike back too far to stop excessive oil smoke on 2 of the cylinders.  I have owned this bike since new and want to get her back into like new shape again

thanks Eric

Answer
Really I'd need a bit more information to be able to offer a definitive answer- which two cylinders ? Smokes only at start-up and first couple of miles, or heavily all the time ? If the smoke is from the right side, then most probably the crankshaft seals are gone and will need to be replaced. If mainly at start-up and then clearing after a couple of miles, then the most common problem is leaking check valves in the oil injection lines at the base of the cylinders. To tell the difference:

- drain the oil from the cylinders via the SRIS valves and check to see if its injector or transmission oil - if its injector oil, then its likely the check valves on the oil injector system - you may be able to flush the valves - do not use blow them out using air pressure as you will ruin them completely - otherwise replace
- take the side cover off the oil tank, and mark the level and let the bike stand over night - check the level after 24 hours and if it has dropped, then its most probably a check valve problem - flush or replace

If its transmission oil then continue

- drain the transmission oil and check for contamination - indicates oil seal issue
- check for oil leak from breather - in cases where the seals is really bad, the transmission will be pressurised and push oil out the breather

- requires full engine tear down and crank rebuild


If none of the above - is the injection rate set correctly ?

Good luck !