1975 R90/6 600 Mile Service post rebuild

[clmedlin]

You need to consider what might be happening. If you do indeed have low pressure and you've been running the engine for a while, there is danger of engine damage.

I'm a little confused. You said in #15 that you put about 150 miles on the bike...no mention of the light. Then in #17 you say that the light is constantly on after 150 miles. Has the light been on for the whole 150 miles or has it not come on after the second 150?

Consider trying a new oil pressure sending unit.

Immediately following the service - I had some intermittent oil pressure light, but it would resolve quickly after I started going. It is now on constantly. I had checked oil pressure prior to the service and was at 78 psi - I can go back and check it again.

My inclination is to also replace the oil filter with the 1 piece variant.

There has to be a connection with the difficulty I had removing the old and installing the new filter.

 

[clmedlin]

You need to consider what might be happening. If you do indeed have low pressure and you've been running the engine for a while, there is danger of engine damage.

I'm a little confused. You said in #15 that you put about 150 miles on the bike...no mention of the light. Then in #17 you say that the light is constantly on after 150 miles. Has the light been on for the whole 150 miles or has it not come on after the second 150?

Consider trying a new oil pressure sending unit.

Immediately following the service - I had some intermittent oil pressure light, but it would resolve quickly after I started going. It is now on constantly. I had checked oil pressure prior to the service and was at 78 psi - I can go back and check it again.

My inclination is to also replace the oil filter with the 1 piece variant.

There has to be a connection with the difficulty I had removing the old and installing the new filter.

I just checked oil pressure - it’s low. 20 psi at 3500 rpm. 4 psi at idle.

 

[20774]

I'm not sure I understand the reasoning behind the 1-piece vs the split filter. There are many many thousands of miles of use by other Airhead bikes with the "bendy" filter. Sounds to me like there's is something inherently wrong with the filter set up or the canister area of the engine. To have pressures that low, especially 4 psi at idle, is very concerning. You probably need to be very careful about running the engine going forward unless you find some silver bullet which explains what's happening.

 

[clmedlin]

When I disabled the bike during rebuild - I did not replace everything. If it was in spec - I re-used it. Hence, when I pulled the oil pump and Checked it - everything seemed good. If my oil pump was bad, could my problem being worsening with every mile I put on it? I really don’t want to pull the engine, but I’ve put a ton of time and money into the rebuild project. Should I pull the engine and re-evaluate the oil pump looking for the “silver bullet”?

 

[20774]

I see where you said you had 78psi oil pressure before rebuild. Now you have 20psi at idle. Something clearly has changed. I personally wouldn't know how to check an oil pump...I know there are specs for it using feeler gages, etc. But you raise some issues. It may not be the filter or the filter housing. It might be the oil pump. We all know that with less than spec oil pressure, the engine's not going to tolerate that for very long. I'm not sure you have much choice but to dig deep to find out what's wrong.

 

[52184]

Stop running the bike, get a replacement filter on hand, then lay the bike on its left side on a blanket or other pad. Remove the covers and inspect/remove the filter. Shine a light into the recess and check to make sure there aren’t any old filter o-rings left on the pipe and lay a straightedge on the pipe—I use a narrow 6” metal rule that works well for such checks.

The filters should never be that difficult to install, so something doesn’t seem right about the pipe or covers. You may have a collapsed filter at this point and need to find out why.

Best,
DeVern

 

[20774]

I went back to your first post...this is a barn find bike? Maybe there's an issue that has been there all along? It was good to hear that you measured 78psi pressure at some point, so that's good. Maybe it's something simple?? Do the easy stuff first. I agree with DeVern that something doesn't sound right with the filter installation. That could be what's wrong.

 

[clmedlin]

Thank you for the collective input. To be clear - I rebuilt a barn find bike that turned over, but was not operable. After finishing the rebuild, I’ve put about 850 miles on the bike. My first indication of a problem was during the 600 mile service.

I will pull the 2 piece filter. Gauge the tube. Look for anything inside the cavity. If everything looks good and a 1 piece new filter slides in without issue, I will start the bike and check pressure. If the pressure is low or I have problems with inserting the new filter, I will pull the engine and start looking at the oil pump / oil system.

If I am missing something - I am appreciative of the help. Thank you all. S/F

 

[clmedlin]

The crazy part is the bike runs great. Sounds great. Is a joy to ride. I just have the oil pressure light coming on.

 

[clmedlin]

I believe this is the cause of my problem - as I went to pull the oil filter the tube that the filter slides onto pulled out while I was removing the internal cover.

 

[kinterridge]

Check out Snowbum's info on the tube installation. Did it have an oil cooler on it when you found it, I believe those tubes are longer than non oil cooler, so just check the specs on the tube that came out. Hope all end well.

 

[clmedlin]

No oil cooler

 

[clmedlin]

Check out Snowbum's info on the tube installation. Did it have an oil cooler on it when you found it, I believe those tubes are longer than non oil cooler, so just check the specs on the tube that came out. Hope all end well.

Thank you. I just read Snowbum’s article - he comments the central pipe is known for coming loose.

 

[20774]

Well, that's certainly something unusual. Note also that at the base of this central pipe is a ball-spring pressure relief valve. If the pressure gets too high, it opens relieving the pressure. Be sure and check that the ball-spring are working. If the ball should stick open, it could be dumping pressure.

 

[clmedlin]

Well, that's certainly something unusual. Note also that at the base of this central pipe is a ball-spring pressure relief valve. If the pressure gets too high, it opens relieving the pressure. Be sure and check that the ball-spring are working. If the ball should stick open, it could be dumping pressure.

I also discover there was a slight ballooning at the tip of the center pipe - that caused the issue with sliding the filter on and off.

 

[52184]

I also discover there was a slight ballooning at the tip of the center pipe - that caused the issue with sliding the filter on and off.

That begs the question of how/why the center tube got ballooned, tho it’s logical to assume it was contact between the backed-out tube and the cover. Probably a good idea to recheck the cannister depth as well, using the info on Anton Largiader’s website. And worth the price of a new center tube to know it is the correct length.

Best,
DeVern

 

[pglaves]

Correct me if I am wrong folks, but didn't the /6 have a filter tube cover inside the outer cover at the engine case?

 

[20774]

Correct me if I am wrong folks, but didn't the /6 have a filter tube cover inside the outer cover at the engine case?

Yes. The /5/6 had flat covers with the inside cover. /7-on bikes had a cover that pushed inside the compartment. See OP's here which shows the flat cover and inside cover.

1975 R90/6 600 Mile Service post rebuild

Hopefully looking for some insight. I completed a thorough 600 Mile service today of my recently rebuilt r90/6. Everything looked good on the bike, it runs well, all the fluids looked good. Had to adjust my valves slightly (all 4) - but my oil filter was an absolute pain to pull out and was...

forums.bmwmoa.org

 

[52184]

Correct me if I am wrong folks, but didn't the /6 have a filter tube cover inside the outer cover at the engine case?

You are correct, retained by a bolt that threaded into the center pipe IIRC. It’s shown in the photo in post# 30.

Best,
DeVern

 

[clmedlin]

I think my biggest lesson learned was when I was doing the rebuild, I wasn’t as thorough as I should have been when evaluating the oil system. I never checked inside the canister (other than cleaning / inspecting) to ensure the center pipe was firmly inserted, nor straight, nor deformed. Since the engine was in a stand (not on the bike) it was easy enough to put the filter on. I never encountered a problem until I went to do the 600 mile service. I am also speculating - but it does not look like loctite was used when the center pipe was inserted. I think when I went to loosen the internal cover at the 600 mile service, instead of loosening the 17mm cover bolt, I probably started backing out the center pipe. I struggled with the filter installation and that probably exacerbated the pipe becoming loose. The riding after the service probably vibrated the center pipe completely off. This would explain why my oil pressure problem was getting worse. I was able to locate a new center pipe from Engles Motors in KC. I will insert the pipe to the required depth and let it sit to allow the locking compound to harden. And then I will insert the new filter and see if my pressure is good. I’m pretty confident this was the “cause” for my pressure loss.

Always open to additional insight - it’s a learning process.