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Oil light comes on at hot idle

ErikK

Just got it firing!
Joined
Jan 24, 2013
Messages
13
The girlfriend has a 750 Breva, she bought it new and it has 23,000 miles on it now so you know she really rides, including long freeway trips. After a long ride in the summer, the oil light will stay on solid when the bike is idling. It started 2 years ago, it would barely flicker on really hot days after high speed runs. Now it does it a lot on ordinary days, so it is clearly getting worse. And I think I hear a new noise in the engine.... :(

I'm thinking I need to check and probably replace the rod and main bearings, and possibly the oil pump. Does that sound about right? Any special tricks or things to check for?

Then there is the question of how to prevent a re-occurence. Checking the dipstick when hot, the oil is smokin' hot, it's pretty scary. A sump extender is probably a good idea, but I wonder if it needs an oil cooler? The larger Breva comes with one. What do the experts say?

And about that sump extender, where can I buy one?

Thanks for any advice!
 
EriKK,

Just found this thread.

https://www.guzzitech.com/forum/202/2572.html

Might help with your choice on sump extender. I thought I saw a sump extender at MG Cycle awhile ago but am hard pressed to find it now.

Sorry, I can't say much about your oil pressure and engine noise. You could try using a pressure gauge to get an oil pressure reading and see if it is varying by much over the different temperatures and RPM.

If the sender is relatively inexpensive you could just change it and see if the issue persists.
 
I pulled the engine, which was pretty easy. Oil pressure sender tests good. There is bearing material in the sump. :-( Split the cases and checked the bearings, one rod bearing (#2) is badly worn, lots of copper showing. Oddly, the other one looks OK. I will post photos if anybody is interested.

Crank looks OK. Micrometer and plastigage seem to indicate that this was caught in time, rods are OK, all it needs is new bearing inserts. Checked the oil pump, it looks OK too. This looks pretty straightforward -- install new main and rod bearings, put it back together with a sump extender.

Anything else I should specially check for? Any suggestions about vendors for these parts?

Wow, the Guzzi shop manual sure has a lot of typos, the torque specs are totally mangled on many items. Under one foot pound for flywheel to crank bolts for example? I don't think so! Anybody have updated torque specs?

The adventure continues...
- Erik
 
Erik,

What's your theory on why the engine suffered low oil pressure?

I'd appreciate pictures, as I have a simple mind.

As for torque values, I get mine from the 2008 UK V7 Classic shop manual. Take a look there.

Joe
 
ErikK said:
The girlfriend has a 750 Breva, she bought it new and it has 23,000 miles on it now so you know she really rides, including long freeway trips. After a long ride in the summer, the oil light will stay on solid when the bike is idling. It started 2 years ago, it would barely flicker on really hot days after high speed runs. Now it does it a lot on ordinary days, so it is clearly getting worse. And I think I hear a new noise in the engine.... :(

I'm thinking I need to check and probably replace the rod and main bearings, and possibly the oil pump. Does that sound about right? Any special tricks or things to check for?

Then there is the question of how to prevent a re-occurence. Checking the dipstick when hot, the oil is smokin' hot, it's pretty scary. A sump extender is probably a good idea, but I wonder if it needs an oil cooler? The larger Breva comes with one. What do the experts say?

And about that sump extender, where can I buy one?

Thanks for any advice!


The SB EFI engines do get very hot under the circumstances described.

This is a common sight after driving a bit inspired - or at hot weather

4158121208_8de98bf3fa.jpg


and personally I'd recommend you to follow the factory specs on oils; the better quality, meaning 10W-60 and absolutely a pure ester-based oil, which are the only oils to withstand the temperatures measured.
Also a Guzzipower (http://www.guzzipower.com) extender will bring you the warm and fuzzy feeling of extra security against running out of oil. The Breva (at least my Breva) WILL consume quite an amount of oil when running fast at hot conditions. At lower speeds none at all.
The spacer will not lower the oil temp noticeable, though.
 
Nobody has mentioned it but do you know what oil viscosity has been used in it ? Guzzi recommends 10w60 because it runs so hot, even a sump extender will not help if the wrong weight oil is used. 20w50 doesn't cut it anymore.
 
Just for piece of mind I'd replace the oil pump. Something had to contribute to low pressure (perhaps in addition to thin oil) and cause the bearing to go.
 
Yeah, I'm worried about why did it happen, and how to prevent a re-occurence, too. My guess is the most likely causes are low oil level or overheating.

Remember this is the girlfriend's bike. She may have been treated badly early in life. She gets much better care now. Hmm, I did not notice that recco for 60w oil! We've been using 20w50 full synthetic and changing every 3000mi or less, but I'm not sure what oil was used the first couple of times. Her previous bikes were water cooled Hondas, much less sensitive to oil.

As you can see one rod bearing is wiped out. Clearance on that one was about .005" too big, plenty to lower the oil pressure. The other one is OK, the smudge you can see across the bearing shell is plastigage indicating a little under .002" clearance.

MG-bearings-118-L.jpg


If there was an oil cooler easily available, I would add it. Anybody know of one that fits? The big Breva comes with one from the factory. Now while the motor is apart would be the time to drill and tap fittings for the cooler lines....

The sump extender is a good idea too. Maybe it adds a bit of cooling, can't hurt. And it makes it less critical if she "forgets" to check the oil. That sort of thing has been known to happen. We'll see if this expensive lesson makes a difference.

I have to say, it is a PITA to check the oil, and almost impossible for a small person to do without a helper. So it's easy for her to put the chore off "just a little". But if we're adding weight to the bike I'd rather add a sump than a centerstand... maybe.

For those who have not had the pleasure of seeing it in person, here is the bottom end of the motor:
mg-engine-929-L.jpg

The connecting rod caps have been removed, and splitting the cases opens up the main bearings, so you can see both the main and rod journals of the crankshaft. The guys in the shop who are used to working on cars said "that's a cute little crank!"

And here is a photo from earlier in the process. As you can see the engine, trans, final drive, swingarm, all come out as a unit. It's really not too bad a job, it was less than three hours for me and my trusty helper.
mg-out-81-L.jpg

I probably have spent another 4 hours or so on teardown and diagnosis, but really it's not bad. These are such simple machines compared to modern Japanese bikes or worse yet cages.
 
Thin oil (too low a weight or too old with the viscosity modifiers broken down), too low an idle, low oil level, and excessive clearance in the oil pump, along with excessive clearance in the bearings, are all things that could have made the oil light come on at idle.
It can be hard to tell which came first.

Which oil to use can be a touchy subject. Staying within the recommended oil ratings is a good idea. But within those ratings there are wide differences. Use your head and you should be OK.
 
Erik,

No one's come up with a workable oil cooler for the smallblock. Not at all. The oil passages don't lend themselves to it.

There's a sump extender from central Europe that includes an oil cooler. I think Teo Lamers might offer it. But, the oil pick up for the cooler is where the oil pump picks up for the engine. It adds 2-3 ft to the oil line, which may cause more problems than hot oil does. Your call on that.

The factory did add an oil cooler to the rare Baja 750 racer. Pickup for the cooler line was in place of the oil filter. So you had an oil cooler, but no filtration. Ok for a race bike where the oil is changed after every meet. Not practical for a regular machine.

Open to your ideas,
Joe
 
chris a said:
Martin at Guzzi piu has recently been offering this cooler and sump extension for the smallblocs....
http://www.guzziepiushop.de/shop/Oelwan ... pter..html
I think it works by thermosyphon.

Yes Chris, that's the one I was talking about. An ingenious design, but I've got reservations. With the cooler the oil pump is now drawing through a much greater distance than it was designed for.
 
I used to be skeptical about nitrided cranks, but no longer. Guzzi may be low-tech in some ways but the casting and machining work in this engine is very nice. I too am impressed that the crank is still good. The difference in diameter from the center of the "bad" journal to the un-worn part of the journal between the two rod bearings is maybe 2 ten thousandths. Like .0002" You can't feel it. But the downside of the high tech nitrided crank is that if it was worn it could not be re-ground, it would have to be replaced.

I looked at the German oil cooler sump adapter. Clever, but I am skeptical about all that plumbing on the suction side of the pump.

A couple years ago I considered machining up an adapter to go in the oil filter hole, for a cooler and remote filter. That's standard race car practice, but there's not much room for a big remote filter on the Breva.

I'll have to look at the oiling passages and think. It's a lot easier to install the plumbing when the engine is apart, it's a freedom that the folks selling aftermarket kits don't have. There ought to be a way to intercept the oil on its way from the oil pump to or from the filter. On the pressure side, before it gets to the bearings. I'm not afraid to drill holes in the block, I've done that sort of work before.

Check out the last page of this.
http://97.74.32.155/files/setrab$.pdf
Some of those look like they might be about right. I'll have to look at the other Breva in my garage, still in one piece, and think about where/if/how there is room to mount a cooler and run the lines. I don't like the way the cooler hangs out in the big Breva, vulnerable in a tipover. I'm thinking mounting it vertically along the front frame tube, maybe inboard sort of between the frame tube and the alternator cover. But it might not get much air flow there, and it might be too close to the front wheel. Or just outboard of the frame tube with a protective bracket around it. Anybody got any ideas?
 
I was looking at images of the big Breva online and can't find the cooler I thought I was remembering. Was it on a different Guzzi model? But it doesn't really matter as I'm not planning to use the factory part.
 
ErikK said:
Anybody got any ideas?

Well, there's Triumph:

crash-bars-triumph-bonneville-t100-one-piece-chrome--18775-p.jpg


The oil return from the heads runs through the cooler. There are variations (aftermarket "improvements"), but the stock unit works fine. Gravity fed, for the most part - no strain on the pump.
 
ErikK said:
Anybody got any ideas?

Well,
yes. I do not think you need to do all that work of necessity. If, do it for fun.
I've been driving through Germany, over and 'round the Alps, Italy, France, Eastern Europe, former Yoguslavia and often fast (-as fast as a Baby Breva will go, that is.. :whistle: ) distances on German motorways, Mediterrainian 40-43* C heat, being idling through cities like Budapest, Milano, Zagrep, Munich, all in summer heat, during the last 9 years - and never really having any problem with overheating.
Yes, the motor do get really hot, but using the recommended oils will make it through. The sumpspacer gives that extra liter of oil, of course, which even if it don't lower the temperature gives that extra amount of oil to tear down.
I'm about 90.000 kms by now, and haven't seen any signs of fatigue yet.
 
What you say makes sense, Holt. The engineer in me says the Guzzi "should" have an oil cooler. But practically, with frequent oil changes and the right oil, it may be "good enough".

And I must not forget that adding the oil cooler and lines and fittings fixes one problem but introduces the possibility of other problems -- leaks, damage to the cooler, pressure drop, etc.

If I were modifying it for more power I'd add a cooler for sure. But since it's the girlfriend's bike and it's stock, and I don't exactly need another engineering project, I think I'll leave it alone.

So if it's not overheating I have to conclude that the root of all these troubles was that somebody let the oil level get too low sometime in the past. Or it went too long between changes and the oil broke down.
 
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