footgoose Posted December 17, 2015 Share Posted December 17, 2015 as long as it's apart, washer replacement seems prudent considering low cost. also giving scud an indicator for continued/future problems when he has an opportunity to look at them again. Link to comment Share on other sites More sharing options...
docc Posted December 18, 2015 Share Posted December 18, 2015 . . . as well as sump gaskets as there may be a leak there which could be the culprit(cavitation). DonG I would like to understand this better? Link to comment Share on other sites More sharing options...
Scud Posted January 2, 2016 Author Share Posted January 2, 2016 I installed the washers and adjusted the valves about a week ago. This made no difference to the oil pressure (as someone correctly predicted). However, I think I may finally have a good lead on my oil pressure issue. I removed the sump and the upper ring - one part of the upper ring gasket was missing. http://www.mgcycle.com/index.php?main_page=product_info&cPath=170_174&products_id=34 If you look at the picture of the upper gasket on MG Cycle website, you'll see two tabs. The smaller tab was totally missing. The oil filter housing had been installed with a metal-to-metal connection on that side. I'm no engineer, but I'm pretty sure that would cause low oil pressure. Now that I can see the crank and connecting rods, should I take off one of the connecting rod ends to look at the bearing? Or what else should I check while I am this deep into it? Please talk to me like I am a novice - because I have never done work on a bottom end before (except for dismantling). Link to comment Share on other sites More sharing options...
gstallons Posted January 2, 2016 Share Posted January 2, 2016 You need to leave them alone . What will happen if you remove and inspect these and you find nothing wrong ? You reassemble and do something wrong , these rod bolts are delicate and have been suspect to fail. Link to comment Share on other sites More sharing options...
gstallons Posted January 2, 2016 Share Posted January 2, 2016 Docc , Footgoose is talking about air getting into the oil intake portion of the lubrication system. Bad for business ! My understanding of the term " cavitaion " is different . Google cavitation to see what you come up with. Link to comment Share on other sites More sharing options...
Chuck Posted January 2, 2016 Share Posted January 2, 2016 Scud, here's how the pressure relief valve works. This is a small block PRV from the Aero engine conversion, but they work the same.. Nothing but a piston closed by a spring. The washers control spring pre load. Simple.. but.. Here's a quicky test rig I made up. Pressure is controlled by an unseen regulator. The Lario PRV blew off at 20 lbs. (!) Washers made very little difference. I used some fine lapping compound, and lapped the piston into the orfice. Viola! 75 lbs. Need I say to clean the lapping compound out very well? I would look here, first. Link to comment Share on other sites More sharing options...
Chuck Posted January 2, 2016 Share Posted January 2, 2016 Ok, I've read the whole thread, now. Thought you were just asking how the PRV worked. I hate to be the bearer of bad tidings, but as I've said many times, "If you look for problems on an old machine, you *will* find them." If that tab on the gasket has been missing for a long time.. I'm betting it has because of the abnormal wear on the thrust washers.. it could very well have had low oil pressure for an extended period. If so, your bearings "might" be toast. What I would do is check the PRV. Put the new gasket on. Check oil pressure. Pressure ok? You probably dodged a bullet. Still low? *Now* it's time to investigate the bearings. Report back before doing that. Link to comment Share on other sites More sharing options...
Scud Posted January 2, 2016 Author Share Posted January 2, 2016 Thanks GStallons and Chuck. This bike seems to have been neglected some before I got it and I've undone a lot of bodgery - but this section of missing gasket just astounds me. The bike does maintain about 80 pounds of pressure on very cold starts - but it drops quickly once it warms up. Therefore, I suspect the pressure relief valve is good. In the interest of scientific experimentation, I may test the bike again with only the gaskets replaced (isolate the variables). PS to Chuck - this is the Red LeMans, which you rode some during our "Scura Rally." It still feels like a good, strong motor - but not so strong as the Mighty Scura. Link to comment Share on other sites More sharing options...
Chuck Posted January 4, 2016 Share Posted January 4, 2016 but it drops quickly once it warms up. Not good. That's a sign of loose bearings. Does sound like the PRV is ok, though.. Link to comment Share on other sites More sharing options...
Scud Posted January 4, 2016 Author Share Posted January 4, 2016 but it drops quickly once it warms up. Not good. That's a sign of loose bearings. Does sound like the PRV is ok, though.. I'm hoping it is a sign that an important part of the gasket was missing - and that the bearings still have some life in them. Stay tuned for parts delivery, reassembly, and testing. Link to comment Share on other sites More sharing options...
Lucky Phil Posted January 4, 2016 Share Posted January 4, 2016 Thanks GStallons and Chuck. This bike seems to have been neglected some before I got it and I've undone a lot of bodgery - but this section of missing gasket just astounds me. The bike does maintain about 80 pounds of pressure on very cold starts - but it drops quickly once it warms up. Therefore, I suspect the pressure relief valve is good. In the interest of scientific experimentation, I may test the bike again with only the gaskets replaced (isolate the variables). PS to Chuck - this is the Red LeMans, which you rode some during our "Scura Rally." It still feels like a good, strong motor - but not so strong as the Mighty Scura. Pressure information without RPM info is a little bit pointless. Ciao Link to comment Share on other sites More sharing options...
Chuck Posted January 4, 2016 Share Posted January 4, 2016 but it drops quickly once it warms up. Not good. That's a sign of loose bearings. Does sound like the PRV is ok, though.. I'm hoping it is a sign that an important part of the gasket was missing - and that the bearings still have some life in them. Stay tuned for parts delivery, reassembly, and testing. Oh, I thought you'd already replaced the gasket, and oil pressure dropped rapidly as the oil warmed up. Carry on.. Link to comment Share on other sites More sharing options...
Scud Posted January 5, 2016 Author Share Posted January 5, 2016 Pressure information without RPM info is a little bit pointless. Ciao True. I already posted that info in great detail in another thread (pressure vs flow). I apologize for bifurcating my problem. It's going to be about a week till I can work on it again - will post results then. Fingers-crossed that I can close-out both threads with a "problem-solved" message. Link to comment Share on other sites More sharing options...
emry Posted January 5, 2016 Share Posted January 5, 2016 Two comments here. A) test rig should simulate the environment that the components work in. Substituting air for oil is a no go. Air just removes the oil that is part of the system. Use air to pressure an oil tank that feeds the test rig, your results might change. 2) Lapping? While I haven't had this system out this is a piston in a tube with radial holes at a determined depth. The piston balances oil pressure (low side + spring pre-load) vs the high side (mechanical oil pump pressure.). What was "lapped" the piston to the bore? Scud, here's how the pressure relief valve works. This is a small block PRV from the Aero engine conversion, but they work the same.. Nothing but a piston closed by a spring. The washers control spring pre load. Simple.. but.. Here's a quicky test rig I made up. Pressure is controlled by an unseen regulator. The Lario PRV blew off at 20 lbs. (!) Washers made very little difference. I used some fine lapping compound, and lapped the piston into the orfice. Viola! 75 lbs. Need I say to clean the lapping compound out very well? I would look here, first. Link to comment Share on other sites More sharing options...
Chuck Posted January 5, 2016 Share Posted January 5, 2016 What was "lapped" the piston to the bore? Have you had one of them apart? The piston seats in the bottom of the bore and closes an orfice. If it doesn't seat, it leaks. It is a perfectly adequate test. Link to comment Share on other sites More sharing options...
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