Solving the oil line problem?
Posted: Tue Dec 31, 2019 1:56 am
Hello,
I have been a long time lurker of the forum as I slowly piece my 75 GT750 back together but I've finally registered and thought I would share some ideas and welcome feedback for a plan I've come up with. It seems the most common problem for a stock GT is the oil pump, lines, and check valves. My originals had a few cracks so I thought i'd tackle the repair while I have the top end at the machine shop. I found a good looking used set on Ebay but found they where also cracked when they showed up. So i've since set out to solve the problem once and for all.
Digging into memory from my days as an engineering student I put together a CAD file for the oil spider/manifold that sits below the pump, and have located some appropriately sized fittings that will allow me to ditch the fragile factory nylon pipes and fit polyurethane tube via a compression fitting. My plan is to have this machined out of aluminum which will last much longer and allow oil line replacement as they get older. The only thing that has me stumped here are the check valves. I have seen one or two other designs that incorporate the check valves into this base ring but this raises some questions for me. If the check valves are moved to the pump end of the line, would this allow air bubbles to be introduced from the pumping action in the crankcase? If so, how is this not the case on the left-most line on the factory assembly, which has the in-line check valve? My thoughts are that if the crankcase pressure does not effect the oil flow in the lines, what is stopping me from getting rid of them all together and instead installing a shutoff valve on the bottom of the oil tank? I'm sure this could all be figured out with some testing, but seeing as my pistons and cylinders are on the other side of town I thought I would instead pose the questions here.
As a side note I have also frequented the Suzuki 2 strokes forum and attempted to register with them, but have been unable to get an activation email. Anyone know the reason?
I have been a long time lurker of the forum as I slowly piece my 75 GT750 back together but I've finally registered and thought I would share some ideas and welcome feedback for a plan I've come up with. It seems the most common problem for a stock GT is the oil pump, lines, and check valves. My originals had a few cracks so I thought i'd tackle the repair while I have the top end at the machine shop. I found a good looking used set on Ebay but found they where also cracked when they showed up. So i've since set out to solve the problem once and for all.
Digging into memory from my days as an engineering student I put together a CAD file for the oil spider/manifold that sits below the pump, and have located some appropriately sized fittings that will allow me to ditch the fragile factory nylon pipes and fit polyurethane tube via a compression fitting. My plan is to have this machined out of aluminum which will last much longer and allow oil line replacement as they get older. The only thing that has me stumped here are the check valves. I have seen one or two other designs that incorporate the check valves into this base ring but this raises some questions for me. If the check valves are moved to the pump end of the line, would this allow air bubbles to be introduced from the pumping action in the crankcase? If so, how is this not the case on the left-most line on the factory assembly, which has the in-line check valve? My thoughts are that if the crankcase pressure does not effect the oil flow in the lines, what is stopping me from getting rid of them all together and instead installing a shutoff valve on the bottom of the oil tank? I'm sure this could all be figured out with some testing, but seeing as my pistons and cylinders are on the other side of town I thought I would instead pose the questions here.
As a side note I have also frequented the Suzuki 2 strokes forum and attempted to register with them, but have been unable to get an activation email. Anyone know the reason?