Topic: air lock in cb750 oil pump

[D DIAMOND]

have tried most ways of purging the oil through after rebuild filled the oilways filled the oil pump tried tilting the engine on to one side I have used assembly lube but I am scared I will ruin the new mains and big end shells there are no bubbles in the oil how long do I crank each time I have also heard about pressurizing the oil tank but do not know how also I am in England and the temp as been about 4deg c I am using 10/30 oil would a thinner oil be ok DD

[bryanj]

Thinner would not be OK have you tried the UK site and asked Trigger

[HondaMan]

This often happens to me during rebuilds (especially when I rebuild the oil pump!).
So, try this:
get an electric heater (not the hot-air type, but the hot-coil or hot-wire type) and fill the oil tank with 10w30 or 10w40 oil, then put the electric heater very close to the oil tank and oil lines, leave it there for at least 3 hours to heat the whole area up and thin the oil. Pull the sparkplugs out of the engine. Then use a larger battery (or 10 amp battery charger hooked up to the bike's battery) and spin the engine (with Run-Off switch in OFF position to save the points) with the starter in 7-second intervals, with 10-30 seconds in between to cool the starter, to start the prime. If it doesn't work within 1 minute the first (or second, or third) time(s), be patient: it will eventually work the bubble through. It also has to fill the oil filter. You will know it made it when the oil light will go out as soon as you start to spin it.

[D DIAMOND]

THANKS VERY MUCH HONDAMAN I TRIED WHAT YOU SAID WITH THE HEATER AT FIRST IT DIDNOT WORK SO I EMPTIED THE OIL TANK THEN KEPT TOPPING UP THE OIL IN THE FEED PIPE THEN TURNED OVER WITH 2 SEC BURST AND KEPT TOPPING UP THE PIPE WITH STRYNGE WHILE THE AIR LOCKS STOPPED THEN DID WHAT YOU SAID OIL PRESSURE STRAIGHT AWAY 70PSI THANKS AGAIN DD

[HondaMan]

THANKS VERY MUCH HONDAMAN I TRIED WHAT YOU SAID WITH THE HEATER AT FIRST IT DIDNOT WORK SO I EMPTIED THE OIL TANK THEN KEPT TOPPING UP THE OIL IN THE FEED PIPE THEN TURNED OVER WITH 2 SEC BURST AND KEPT TOPPING UP THE PIPE WITH STRYNGE WHILE THE AIR LOCKS STOPPED THEN DID WHAT YOU SAID OIL PRESSURE STRAIGHT AWAY 70PSI THANKS AGAIN DD

Good job!
Merry Christmas!