low oil pressure?

I replaced the filter and oil yesterday and gave it a small run around town today and it is now worse when the motor is hot. Now it happens under 2000, but as the rpm's rise the light flutters a bit.

Maybe I should drop the pan and check to make sure the main passage isn't clogged. But just dont' get why it only comes on when the bike is hot.

any more tips?

it happens when it get's hot because oil will thin out as the temp goes up, the reason that it is worse is because you went to a lighter oil, you need to see how low your pressure really is , put a guage on it, you can get one from the auto parts store or borrow one, warmed up you will probably only see a few pounds maybe 4 or 5 psi if you have that then your probably going to need a pressure switch, you also might want to go to a thicker oil depending on your climate, lets us know how this works out

forgot to tell you oil pressure is developed from you crank and crank bearings if you got no pressure hot at idle the your looking at bearings, did you examine the
crank when you replaced the bearing or bearings if it was scored in any way you should have had it machined otherwise you'll end up with problems like your having

This is the kind of response i've been looking for. I didnt' know the pressure was made by them. I didnt' have to replace bearings as it was a used motor and just needed a piston. I'll tear this motor apart this up coming week hopefully with my new project that i'm picking up from Detroit this upcoming week.

I'll let you guys know if it was a bearing or not. I'm still trying to figure out how the crank/bearings create the oil pressure. Huh, so much for me being an engineer LOL.

Steell, check PM's i'm very interested as I have a business partner as of now with this bike.

Well, that's one way of putting it
The oil pump pumps the oil, and if there is no restriction then there is no pressure, just lots of flow. The main and rod bearings have fairly tight clearances and restrict the flow of oil, thus causing pressure to rise. IIRC, every line except the one feeding the mains (and thus the rods) has a restrictor in the line to limit the flow (which increases the pressure).
I'll have to check the manual later, but I think the rated pressure on the 650's is around 30 psi at 3k rpm, althiugh I'm not real sure at the moment, it could be higher. The 1000's run somewhere around 5 psi because of roller bearing cranks (very little restriction).

Quoted from my previous posts above:

As the oil warms up the thickness of the oil decreases, so pressure drops, although if pressure drops far enough to trigger a good sensor, then you do have a problem.

(4) Clearances exceed service limits (remember that 750 motor I mentioned?)

By clearances I mean any lubricated bearing surface, like the main, rod, and cam bearings.

But when you said the motor only had 13k miles on it, then that lowered the probability of bad bearings, it's still possible, but that made me want to check everything else first (expecially the easy stuff).

Post edited by: steell, at: 2006/04/15 03:03

steel i whole heartedly agree with you, incognito please check your pressure before you tear apart that motor may save yourself some down time and a crap load of money!!!!

I've been looking through my clymer's manual and can't find anything on how to check the pressure. I've seen gauges that go where the oil fill is, but I don't need one of those.

What type of pressure tester am I looking for and where to I put it to check the pressure.

you need a oil pressure guage 0-50 psi you would install it right were your pressure sender is, the one that goes into the fill is for temp not pressure, let me see if i can find one
here is one on ebay a little more than you need but it would work

Post edited by: jbw7300, at: 2006/04/15 16:27 cgi.ebay.com/ebaymotors/NEW-ENGINE-OIL-P...dZ1QQsspagenameZWDVW

Post edited by: jbw7300, at: 2006/04/15 16:28

It goes right below the ignition cover on the right side of the motor, directly below the oil pressure sensor. Manual says 28-36 psi at 4k rpm with engine warmed up (higher if cold), 90 degrees C.
Just a thought here, when you had the block of the case, did you make sure the two oil passge orifices were in place (one at each end of block, between the case and block)? If not then you could be pumping a lot of oil into the cam cover and reducing the pressure considerably. I think that if that were the case, when you start the motor the oil level would fall below the sight glass rather quickly (but I don't remember how fast and how far the oil level falls in normal operation). And you really should drop the oil pan and check the oil pickup screen if you did not do that when you assembled the motor.

A 100 psi gauge would be better, as the max pressure cold is 85 psi, that's when the relief valve is supposed to start relieving pressure.

You will probably need a pipe thread to metric thread adapter, because oil pressure gauges are usually pipe thread, and the test port is more than likely metric thread.

Post edited by: steell, at: 2006/04/15 16:46

Ok, so i've got the information now. All I need to do is get a gauge. Hopefully i'll find one locally by monday.

Thanks for the link jbw, now I know what to look for.

Steell, are you talking about the "nipples" on the top of the case? if so, then I believe they are there with an o-ring around it. Jarhead (Dave) and I put the motor together a few months back. My memory is failing these days.
Also, as you said in your PM wednesday works for you. We'd be leaving Kenosha WI in the morning. Swinging down by you in the day and then up to Detroit sometime later. If you'd send me a PM with your address and number that would be great. I hope cash is ok

Ok, just thought I'd ask because the oil pressure would be real low if they were not there

Post edited by: steell, at: 2006/04/15 23:24