Topic: Oil light is coming on after a spirited run...why?

[KCRSXTypeS]

Hey guys, just been riding my 500 a little and I've noticed that after I run it hard up to 6K or more, when I let off the oil light comes on when at idle.  If I increase the RPMs at all then it will go away.  If I turn off the bike and wait a few minutes then the light goes away and stays off.  Could this just be a tweaky oil pressure sensor?

[UnCrash]

I had a similar problem on my 750 and was advised that the sensor was probably bad.

I replaced it with an old one from a parts bike and it operates normally now : ).

My guess is that it's failing on you.  Should be cheap to replace.

Best o luck.

[bistromath]

Could also be a failed oil pump, worn main bearings, or any number of other things. Best to get an oil pressure sender and mount it up to see.

[tlbranth]

It's usually a bad sender/switch. But I have a mechanical guage I hook up to cars/bikes whatever needs checking - just to make sure. Wouldn't hurt to get one.

[KCRSXTypeS]

Where would this checker hook up to?  The oil filter bolt hole?

[HondaMan]

Also, try using 20w50 weight oil, or at least 15w40 weight. If you are running 10w40 oil in the summer, this can hapen, even on anotherwise OK bike. If you are running oil lighter than this, then the next thing you should be doing is: changing your oil. 

I recently had a rider come through my [backyard shop] who had 5w20 Mobil 1 in his 550 (from the PO). This thin oil slipped out past seals everywhere under pressure, and caused heating of the O-rings in the oil pump's feed passages from the leaking oil, which immediately shrank them and made big-time leaks. The top end of the bike rattled loudly, too. Changing to 20w50 oil (after replacing the damaged O-rings) solved it all.   

[KCRSXTypeS]

Also, try using 20w50 weight oil, or at least 15w40 weight. If you are running 10w40 oil in the summer, this can hapen, even on anotherwise OK bike. If you are running oil lighter than this, then the next thing you should be doing is: changing your oil. 

I recently had a rider come through my [backyard shop] who had 5w20 Mobil 1 in his 550 (from the PO). This thin oil slipped out past seals everywhere under pressure, and caused heating of the O-rings in the oil pump's feed passages from the leaking oil, which immediately shrank them and made big-time leaks. The top end of the bike rattled loudly, too. Changing to 20w50 oil (after replacing the damaged O-rings) solved it all.   

This could solve my problem.  I am running 10W40.  What brand of oil do you use?  I hear we shouldn't use oil with any additives so I am running 10W40 for vehicles before '84.   I think 20W50 would be better and besides, I have put about 50 mi. on my bike on this oil after the bike hadn't been run for 25 years.  I think it has cleaned a bunch of crap out and it wouldn't be a bad idea to change the filter and oil again.

[tlbranth]

Where would this checker hook up to?  The oil filter bolt hole?

Remove the switch and hook up the guage there.

[KCRSXTypeS]

Where would this checker hook up to?  The oil filter bolt hole?

Remove the switch and hook up the guage there.

ah...gotcha.  I assume I can pick up this gauge at any autoparts store?  Is the switch easy to get to?

[tlbranth]

Is the switch easy to get to?

On my 750 it's behind the cylinders with a rubber cap going to it. One caveat: Years ago (like almost 40) I put VDO guages on the 750. In order to connect the oil pressure guage AND the light switch, I installed a T-fitting. Problem was, the US pipe thread and the Japanese thread weren't quite the same. If memory serves, the tpi were the same but the taper was different - or some such. At any rate, I tapped the thread in the engine to US standards for the fitting. One of the outlets is capped now because the guages are off the bike. All said, it may be worth checking that your guage threads match the JIS threads on the bike. Probably a Japanese model would fit. Well worth having a guage to check such things. Good luck.

[bryanj]

On the 500/550 its on top of the pump just in front of the front sprocket

[voxonda]

On my replica during trackdays I see this fenomana also. Used Castrol 10W40 and saw the pressure drop to 0 on the gauge in low rpm corners. changed to 20W50 and just let it warm up a bit longer, and no problem at all. Also changed my cooler to a larger one.

[KCRSXTypeS]

On my replica during trackdays I see this fenomana also. Used Castrol 10W40 and saw the pressure drop to 0 on the gauge in low rpm corners. changed to 20W50 and just let it warm up a bit longer, and no problem at all. Also changed my coller to a larger one.

So use Castrol 20W50?  My clutch is acting kind of funny...almost as if there is no friction zone.  Could this be the oil as well?  I think I need to adjust my clutch but I have only adjusted the cable and not that screw in the sidecover.  I dont exactly understand how that screw adjusts the clutch so I haven't messed with it yet but I think the clutch needs adjusted but maybe the oil will help too, idk.

[HondaMan]

On my replica during trackdays I see this fenomana also. Used Castrol 10W40 and saw the pressure drop to 0 on the gauge in low rpm corners. changed to 20W50 and just let it warm up a bit longer, and no problem at all. Also changed my coller to a larger one.

So use Castrol 20W50?  My clutch is acting kind of funny...almost as if there is no friction zone.  Could this be the oil as well?  I think I need to adjust my clutch but I have only adjusted the cable and not that screw in the sidecover.  I dont exactly understand how that screw adjusts the clutch so I haven't messed with it yet but I think the clutch needs adjusted but maybe the oil will help too, idk.

Castrol makes an oil called "4T Motorcycle Oil", which is perfectly designed for these bike engines. The regular Castrol (and Valvoline, for that matter, among others) has too much detergent in it, to prevent sludge problems: this stuff foams in these engines and can cause low oil pressure, very common.

You need to use motorcycle oils, or full synthetics, or Diesel engine oils. 

[tlbranth]

hondaman - I thought you were opposed to synthetics in th sohc engine?

[voxonda]

I used the "4T Motorcycle oil". The red one.

Rob

[KCRSXTypeS]

On my replica during trackdays I see this fenomana also. Used Castrol 10W40 and saw the pressure drop to 0 on the gauge in low rpm corners. changed to 20W50 and just let it warm up a bit longer, and no problem at all. Also changed my coller to a larger one.

So use Castrol 20W50?  My clutch is acting kind of funny...almost as if there is no friction zone.  Could this be the oil as well?  I think I need to adjust my clutch but I have only adjusted the cable and not that screw in the sidecover.  I dont exactly understand how that screw adjusts the clutch so I haven't messed with it yet but I think the clutch needs adjusted but maybe the oil will help too, idk.

Castrol makes an oil called "4T Motorcycle Oil", which is perfectly designed for these bike engines. The regular Castrol (and Valvoline, for that matter, among others) has too much detergent in it, to prevent sludge problems: this stuff foams in these engines and can cause low oil pressure, very common.

You need to use motorcycle oils, or full synthetics, or Diesel engine oils.  

I used 20W50 Valvoline Motorcycle oil but I am still getting the oil light.  Im not really worried about it because it doesn't sound like the bike is starving for oil and Im sure its just a faulty switch.

[MoTo-BunnY]

My CB500 was flickering the oil light at idle a lot. I went to Castrol Tection Extra 15w40 oil for diesels (big green jug at Wally World was like $10) and it cut it the flickering way down. Eventually though, I scored an oil pump with low miles on it (like 5000) off of feeBay and installed it (as they are over $150 new).

I  have never seen a flickering oil light at idle since (even with our recent 100+ degrees, which is super rare for PDX town). Also, it got rid of the upper engine clicking (that I thought was normal. . yikes.. .  .must have been mild oil starvation)