1975 R90/6 600 Mile Service post rebuild

[20774]

So did you find a smoking gun as to the cause?

 

[clmedlin]

So did you find a smoking gun as to the cause?

Probably not. The springs on both the canister valve and the pressure valve at the timing chain were shorter than the new springs by about 1mm each - the new springs were a bit bigger than spec. The center pipe was obviously bad. When I opened the timing chain cover, oil pooled onto the floor. Not sure if that’s normal. My biggest learning cure was the spring valve in oil canister. That is a pain to replace. I had to lean the bike almost all the way over to get the new ball bearing and plug inserted. I am hopeful the problem is resolved, but researching extensively the internet, low oil pressure seems to be a gremlin others have chased. I really don't want to pull the engine just because I just finished a 13 month rebuild to get this thing going and I want to ride it. I have a Lang oil pressure gauge and it was not very good. It’s cheaply made and doesn’t seal very well. Sadly it looks like most of the adapters are made in china, so the extra expense of buying “made in the USA” was not worth it. I was left questioning the accuracy of it in the end. I am super appreciative of the support and recommendations I’ve gotten on this forum. Most of you immediately mentioned the valve in the oil canister and I think that replacing the springs in it and in the timing cover valve made the difference. If I post again on this thread, then nothing worked and I’m pulling the engine. Thank you. S/F

 

[20774]

I commend you for being so persistent! Thanks for giving us the "blow-by-blow" as it were. We'll all be interested in the results one way or the other.

 

[Lendog]

Thank you. I went back to the 1 piece filter. I also tore the front and bottom end of the bike apart - looking at the sump, oil filter canister, and oil pressure valve above the timing chain. I was finally able to get my oil pressure up - and when I reinstalled the switch (after taking off the oil gauge), the light went off immediately after starting the bike. I will verify timing again before I button up the front end and hope to test the bike this weekend.

I rode a r90/6 for 19 years the only issue I ever had was 1 of the centerstand springs broke when I was going through the Holland Tunnel,
It was quite a surprise to see sparks in the mirrors, It did not help my closterfobia, sorry I’m refreaking myself out and can’t even spell it

 

[clmedlin]

I thought I would update the group and see if there is any wisdom to be shared. After my last post, I had about 19 psi at idle and 55 psi at 3500 rpm on a cold engine. Went for a test ride and about 3 miles in, the check oil light would flicker when I engaged the clutch and would come to a stop. I have started disassembly to replace the rotors in the oil pump. When I pulled the valve covers, I noticed there was quit a bit of play in the valve clearance (intake and exhaust) - I’m curious what collective thinks would have caused the clearance to expand in such a short period of time. And could this be the underlying cause of my oil pressure issue.

Any insight would be appreciated.

 

[20774]

I doubt valve clearance has anything to do with oil pressure. As for why they increased, it's hard to know. Could be that they were set off the last time, the nuts weren't tight, etc. I think you should just reset them properly to ensure they are the right clearances, then check them again in the near future.

 

[drost]

Couple of thoughts after following this thread. I would check to see if the inner cover is sealing at the oil canister. Looks like there was some issues in that area. I would check that by removing spark plugs and the outer filter access cover and crank the engine over and see if any oil is leaking past the canister. Don’t forget to ground the spark plugs. The canister is pressurized and there should be no oil seepage. The next thing I would check is the oil pickup tube for being loose or blockage. Good luck.

 

[clmedlin]

Couple of thoughts after following this thread. I would check to see if the inner cover is sealing at the oil canister. Looks like there was some issues in that area. I would check that by removing spark plugs and the outer filter access cover and crank the engine over and see if any oil is leaking past the canister. Don’t forget to ground the spark plugs. The canister is pressurized and there should be no oil seepage. The next thing I would check is the oil pickup tube for being loose or blockage. Good luck.

I appreciate the insight. I’m in the process of disassembly to get to the oil pump and examining everything along the way - so I can’t check pressure in the oil canister. However, since I have the bike open is there something I could do to identify a potential issue in the canister? Thank you in advance.

 

[Lendog]

I thought I would update the group and see if there is any wisdom to be shared. After my last post, I had about 19 psi at idle and 55 psi at 3500 rpm on a cold engine. Went for a test ride and about 3 miles in, the check oil light would flicker when I engaged the clutch and would come to a stop. I have started disassembly to replace the rotors in the oil pump. When I pulled the valve covers, I noticed there was quit a bit of play in the valve clearance (intake and exhaust) - I’m curious what collective thinks would have caused the clearance to expand in such a short period of time. And could this be the underlying cause of my oil pressure issue.

Any insight would be appreciated.

My r90/6 was balanced and would idle at 550rpm but the oil pressure would be too low, a 600 engine will also idle low easily,
usually 10 psi / 1000 rpm is recommended, the oil pump does consume horsepower

 

[AntonLargiader]

It sounds like you have covered the bases on the oil system itself. The canister, pickup assembly, and the front pressure relief valve are the main parts to hit. unless your oil pump parts were visibly damaged, they are not going to be suddenly at fault where they weren't before.

I wonder if using 5W40 oil on your initial run, along with whatever pre-existing wear that engine had, has created a situation where you simply have excessive bearing clearances and are losing oil pressure the old fashioned way.

In order to have good oil pressure you need to a) generate it, and b) contain it. Generating it is having a good pump and a leak-free pickup. Containing it is a leak-free filter assembly, good bearing clearances, and a good pressure relief valve at the end. What did the oil look like when you drained it at 600 miles?

 

[clmedlin]

It sounds like you have covered the bases on the oil system itself. The canister, pickup assembly, and the front pressure relief valve are the main parts to hit. unless your oil pump parts were visibly damaged, they are not going to be suddenly at fault where they weren't before.

I wonder if using 5W40 oil on your initial run, along with whatever pre-existing wear that engine had, has created a situation where you simply have excessive bearing clearances and are losing oil pressure the old fashioned way.

In order to have good oil pressure you need to a) generate it, and b) contain it. Generating it is having a good pump and a leak-free pickup. Containing it is a leak-free filter assembly, good bearing clearances, and a good pressure relief valve at the end. What did the oil look like when you drained it at 600 miles?

Thank you for the insight. I agree completely with your assessment on my oil. I didn’t realize an older motor worked better on thicker, mineral based oil and I probably caused my issue. This was / is a project designed to help me learn. After I get the back end reassembled, I plan on pulling the connecting rods and replacing the rod bearings. I have some wear on my wrist pins (very minor) and I need to gauge the front end (small end) of the connector rods as well. Those sleeves may need to be replaced. There is no blueing or scorching on any of the pistons, heads, crank or any of their sub components. So I feel confident, no damage was done. But I may have caused some wear on already worn parts. Truly appreciate your feedback. Thanks

 

[omega man]

Thank you for the insight. I agree completely with your assessment on my oil. I didn’t realize an older motor worked better on thicker, mineral based oil and I probably caused my issue. This was / is a project designed to help me learn. After I get the back end reassembled, I plan on pulling the connecting rods and replacing the rod bearings. I have some wear on my wrist pins (very minor) and I need to gauge the front end (small end) of the connector rods as well. Those sleeves may need to be replaced. There is no blueing or scorching on any of the pistons, heads, crank or any of their sub components. So I feel confident, no damage was done. But I may have caused some wear on already worn parts. Truly appreciate your feedback. Thanks

Whatever the outcome, your mechanical skills-
OM

 

[clmedlin]

Whatever the outcome, your mechanical skills-
OM

Dude - this forum is amazing in sharing knowledge! It’s the best perk IMO of the MOA.

 

[kbasa]

Dude - this forum is amazing in sharing knowledge! It’s the best perk IMO of the MOA.

It's turned out to be what we hoped it would be when we set it up 20+ years ago. Super glad it's working for you.

 

[clmedlin]

It sounds like you have covered the bases on the oil system itself. The canister, pickup assembly, and the front pressure relief valve are the main parts to hit. unless your oil pump parts were visibly damaged, they are not going to be suddenly at fault where they weren't before.

I wonder if using 5W40 oil on your initial run, along with whatever pre-existing wear that engine had, has created a situation where you simply have excessive bearing clearances and are losing oil pressure the old fashioned way.

In order to have good oil pressure you need to a) generate it, and b) contain it. Generating it is having a good pump and a leak-free pickup. Containing it is a leak-free filter assembly, good bearing clearances, and a good pressure relief valve at the end. What did the oil look like when you drained it at 600 miles?

Thank you for your insight Anton. I have learned a lot about my bike over the last 18 months - the barn find rebuild was one learning curve. The other was problem solving. I am confident my issue is resolved - I replaced the connecting rod bearings. Additionally, I discovered things that I could have done better. I also learned I was not as thorough as I thought. I learned about plasti gauge and how to use it. You can’t test bearings (connecting rod) by pulling on them or shaking them looking for lateral play - there clearances are just too tight. The help and expertise shared here is top notch. S/F