Oil pressure question

I recently changed my oil for the season, I was running Mobil1 15/50 full synthetic with no issues at all! I switched that out with Rotella 15/40 only because it's way cheaper, I noticed now, and for all I know it was doing this befor but I didn't pay attention, but if the bike has been sitting over night and I go to start it, it takes a while for it to build pressure and the light to go off. If it's been sitting for a couple hours light goes out almost instantly? I assume this is because the filter has no oil and that's in the area of the sensor, does this bike have a anti drain back valve like a car? I pulled the filter and inspected it had about 1500 miles so I left it in, however I noticed a bolt with a spring and ball, I removed and cleaned, that I think is a bypass valve. Basically wanna know if this is normal and if there is a drain back valve, where is it so I can inspect? I'm b would say it takes a solid 4-5 seconds to build pressure, again maybe this is normal given the the thick viscosity of Rotella. Thanks in advance folks!
1977 kawasaki kz750 twin.

Always replace the filter with the oil.
Steve

Yeah I ordered one from o'reilly's, it will take a couple days, they sell it to me for 6.00 where as the dealer (no surprise) is 14.99

If yours is like mine it's a Wix filter. Slightly larger but I don't think better. I see some sales on eBay for three or more. next time I'll buy them. Most used and important filter on the bike.
Steve

New 750 wrote: I recently changed my oil for the season, I was running Mobil1 15/50 full synthetic with no issues at all! I switched that out with Rotella 15/40 only because it's way cheaper, I noticed now, and for all I know it was doing this befor but I didn't pay attention, but if the bike has been sitting over night and I go to start it, it takes a while for it to build pressure and the light to go off. If it's been sitting for a couple hours light goes out almost instantly?

I have a 1979 KZ750 twin and it does exactly the same thing. If it hasn't run for a few days, the light can stay on for a couple of seconds. Mine has 80k miles so I assume it is wear in the bottom end (main bearings) and it takes the pump longer to get pressure up. I did replace the oil pump at 70k but the pump was fine. It just takes longer to get the engine pumped up with oil after it has all drained down.

Your bike has 80k,wow I didn't even think that possible on a twin! I just hit 35k.i assumed mine was at the farther end of its life, it runs like a champ though,

Maintenance.
Steve

And perseverance. Had to do the head/valves at about 40k, at 70k valves and rebore.

Yeah, third overhaul in 40 years. Not many guys can say that. I get complements from some people but when I tell them I bought it at 21 (I'll be 61 soon), I get the OL FISH EYE. :woohoo:
Steve

I bought mine new when I was 26 years old, now I'm 62.

What's a 62 year old man doing on a motorcycle?

Same thing as a 26 year old, but not as often.

swest wrote: Always replace the filter with the oil.
Steve

+1

bountyhunter wrote: I bought mine new when I was 26 years old, now I'm 62.

What's a 62 year old man doing on a motorcycle?

Same thing as a 26 year old, but not as often.

LOL! Hey bountyhunter! , I hear ya!! Im 65, still riding and plan on it as long as I can!
Regards
Ed