76 R90/6 - oil light at idle/low rpm, no oil light while riding

[concernedparent]

76 r90/6, 28K miles.

took the bike out over the weekend for a 250 mile ride from queens, ny down to manahawkin, nj. a lot of highway riding @ 70-75mph. very humid all day, rode through two short rain storms, and floating around 80-90 degrees all day long. oil change was done about 750 miles ago. checked oil level before leaving for the trip and it was close to the 2L mark. bike has never had any issues with the oil light / oil pressure in the 2+ years i've owned it, it only comes on when i turn the key from off along with all the other idiot lights.

upon returning from 249 of those miles, on the 1 mile back to the garage while coming to a stop at a light, the amber oil light came on. when i came to a stop the light remained lit. taking off from the light over ~1300RPM the light flickered, then went out. the light came back on at the next stop light. same thing happened after taking off, shifted into second and revved the bike and the light goes out. when i got back to the garage and let the bike return to idle the light came back on. after getting off an inspecting, i didn't see any significant leaks or smoke coming from the bike, the motor was noticeably warm. i did not check the oil while the motor was hot, it was 11:30PM and i was ready for bed at this point.

also just want to point out from other threads i've checked this is indeed the amber oil light and not the red generator light.

came back the next day and checked the dipstick, the oil mark is maybe the slightest touch lower, but is pretty close to the full mark. no evidence on the ground of any oil leaks. visual inspection around the bike looks okay.

where to start with diagnosing this? is running the motorcycle at all dangerous at this point even just to see if the light goes out?

 

[20774]

The oil light should never really come on once the engine is started, so this could be serious. First thing I would say is to change the oil pressure sending unit and see if that cures the problem. If not, then you should park the bike until more diagnoses are done.

 

[concernedparent]

The oil light should never really come on once the engine is started, so this could be serious. First thing I would say is to change the oil pressure sending unit and see if that cures the problem. If not, then you should park the bike until more diagnoses are done.

by "sending unit" do you mean the pressure switch? so it would be take out the switch and do an oil change? removing the switch would allow the oil to drain out correct? or no?

https://www.euromotoelectrics.com/Oil-Pressure-Switch-for-BMW-R-Airhead-p/ops-414.htm

 

[jhall]

Oil Weight?

What weight of oil are you using? Also, what is your bike's idle RPM?

 

[concernedparent]

What weight of oil are you using? Also, what is your bike's idle RPM?

liquimoly 20w-50. idle RPM is right around 900-1000rpm. coming to a stop it usually drops to about 900rpm and the gen light starts to come on, blip it once and it'll float around 1050-1100.

 

[pauls1150]

Yes the pressure switch, only a little will dribble out so no full oil change necessary. You may be able to just lean the bike over to the right a bit.
Also try to trace the wire to it (and make sure that connection is clean and dry), look for any place where the insulation is damaged or the wire may be broken inside.
Make sure you get the right one for your specific year & model.

 

[stevenrankin]

Possible oil filter problem

It is possible to get blocked or low pressure from a oil filter problem. Not saying you installed the filter wrong at the last oil change (if you changed the filter). It would perhaps be a good idea to check to see if the filter is in correctly, there is not something fishy going on with the filter. Since it is not winter, the usual problem of a collapsed filter is less likely to happen but who knows?

I go with the thought that if something happens shortly after I work on something, the last thing I recheck my work.

Other than that, it could be just a bad switch, connection, or wire. St.

 

[dennisdarrow]

Mainly though.......If the problem persists, and UNTIL YOU FIND THE PROBLEM. Run the engine on a minimal basis. Meaning, start it, run at idle, increase til light goes out and STAYS OUT when returning to idle. If the light comes back on at idle, KILL THE ENGINE and figure something else out. Hopefully you have found the issue.

 

[RPGR90s]

Oil Light

I would definitely do an inspection on the oil filter that was last installed. If it's a one piece filter, verify that the inner o-ring wasn't left behind on the center tube. If it was left behind, then it can cause the new filter not to seal properly, resulting in a loss of pressure.

Hope you figure it out.

 

[concernedparent]

yeah the last oil changes (2, once a year) that i've done i haven't touched the filter. is it worth it to do an oil change/filter change as well as swapping out the sensor at this point?

inspected the swtich wiring last night and didn't see anything funky connections or nicks in the wire. ordered a new sensor from boxer2valve, confirmed it was for /6's.

 

[oldnslo]

I had the exact same problem when I first acquired my '92 R100RS 9 years ago.It turned out that the person who did the oil/filter change before I got the bike had put two (!) gaskets under the metal cover over the filter chamber, meaning they didn't bother to scrape the old gasket off and slapped another one on there. This upset the critical relationship with the white ""2000 $ o-ring" and the filter canister, and could have lunched the engine if I had continued riding. Carefully measuring the filter canister dimensions and properly installing a new filter cured the problem before any damage was done, and I've put 15k on the bike without problems since then. I would definitely check this out before riding further.

Adam

 

[galaxie]

oil light

you might try removing oil pan see if the bolts on the pump are tight

 

[20774]

This upset the critical relationship with the white ""2000 $ o-ring" and the filter canister, and could have lunched the engine if I had continued riding.

The /6 was the last year of the older style filter arrangement...it's not the $2000 o-ring configuration that showed up with the 1977 models. Anton documents the configurations here:

http://largiader.com/tech/filters/

 

[RPGR90s]

Oil Light

yeah the last oil changes (2, once a year) that i've done i haven't touched the filter. is it worth it to do an oil change/filter change as well as swapping out the sensor at this point?

inspected the swtich wiring last night and didn't see anything funky connections or nicks in the wire. ordered a new sensor from boxer2valve, confirmed it was for /6's.

It's up to you. I like to troubleshoot to see what the exact problem is, but those are both areas that are suspect. If you don't want to look at the oil filter, then by all means, get a new sender unit.

All things being equal, Airhead's are pretty bulletproof in terms of oil pressure issues, so hopefully it's just a faulty sensor or something amiss with the oil filter assy.

Note: per the photo, your filter has an o-ring/seal at each end of the filter with an inner cover (6) and bolt (5) to seal it. The outer cover and gasket is separate and should have no bearing on this issue.

 

[pglaves]

I suspect a loose inner cover. #6 in the parts shown in post 14.

 

[oldnslo]

"The /6 was the last year of the older style filter arrangement...it's not the $2000 o-ring configuration that showed up with the 1977 models."

Kurt, thanks for setting me straight on that

 

[concernedparent]

so looking at maxbmw parts fiche there's a straight filter (11 42 1 337 572) you can buy or there is a "folding filter." ( 11 42 1 337 570). There also is a parts kit "11 00 9 056 145 SET: REPAIR KIT FOR OIL CHANGE" which includes two rings and a o-ring. Is there any difference between the straight filter and the one that folds?

is this what i need for the filter change? considering i didn't change my filter on the last two oil changes over the past two years this should receive some attention.

 

[m_stock10506]

There is no functional difference between the straight filter and the hinged one. The hinged one is easier to slide into the chamber (and remove) depending on the model bike that you have. I would buy the kit, that way you will have a new crush washer and whichever o-ring or gasket is needed for your bike. Just make sure that you aren't buying the filter for a bike with an oil cooler - if you don't have one.

 

[20774]

Theoretically, the hinged filter would actually be stronger in terms of it collapsing. The unhinged filter has the full length that is unsupported whereas the hinged filter has the metal ends that meet when inserted, so the "free" length of the filter element is reduced.

 

[concernedparent]

ok so everything is finally here, maxbmw oil filter took 2 weeks to get here for some reason....

...is there any recommendation as to if the sensor would be the first thing to check or if the oil filter would be the culprit? i have a feeling i'll be doing both for peace of mind but figured i would ask...thanks everyone for your responses.