Topic: CB750. - sumpthing or oil pump?

[macvit7906]

Hello all. running into issues with the sumpthing (or maybe just my oil pump) - tips/help appreciated!

Installed the sumpthing yesterday. Very well made piece and BertJan has been great to work with.

Running into issues with oil pressure though. I'm using a freshly rebuilt pump that worked great just a few days ago on a freshly rebuilt engine and first start up (60-70psi).

Installed sumpthing successfully, filled the sump with 3 liters of oil. Using the starter motor to check pressure (this usually gets me 40 psi) - I get no oil pressure. So i remove the oil filter housing and get no oil squirting after 3 or 4 30 second bursts - so the pump isn't taking oil.

For some reason my oil pump is really touchy. If any air at all is introduced, it loses prime. I've had to re-prime the thing working the air relief valve many times just go get it to work initially. (maybe the new air relief spring is too strong? )

How exactly is oil pumped with the sumpthing if the intake port is blocked? If initially the pump has to suck any air, then that is for sure what happened.

I'll pull the pump again today to check things out, but does anyone know what could be going wrong?

I'm thinking about attaching the oil tank with just the oil intake hose hooked up and pumping till the sump is full, that way the pump stays primed?

[69cb750]

Oil flows down hill from tank into pump displacing any air.
If you are trying to suck oil up hill into pump then pump needs to be primed, all air removed.

[chrissprior]

Hi looking at installing sumpthing as well have you resolved the issue and does the conversion work OK ?  Cycle X have a tech article on priming the engine with oil using a drill on the pump drive it may help you

[macvit7906]

Hi looking at installing sumpthing as well have you resolved the issue and does the conversion work OK ?  Cycle X have a tech article on priming the engine with oil using a drill on the pump drive it may help you

I did resolve the issue. When putting the sumpthing together, your pump will lose it prime. I had to get a tub that could fit the whole sumpthing assembly after it is put together with the oil pump attached, fill it with 3-4 quarts of oil so the whole thing is submerges, and then re-prime the pump again by spinning the wheel of the pump back and forth until there are no air bubbles and you feel resistance on the pump gear.

Then install onto the engine. It will get messy, have plenty of towels handy.

Now the bike has better pressure than it did without the sumpthing.