Topic: Sigh - burning oil after a top end rebuild :(

[Tim.]

So, last spring, in order to get my 550F on the road once and for all, I ended up sprining for a top end rebuild.  I got a set of pistons/rings etc. that worked out to a 0.5mm overbore on the stock 550.

Long story short, the work was done by a reputable shop, and 1500 miles later, I'm burning oil.

So, my question is, what are the major causes of burning oil?  The only obvious thing in my mind is the pistons/rings and valve seals.  Anything else?  Is a leak-down test the only definitive way to confirm where the problem might be?  I had the valves done at the same time, including new (aftermarket) seals.

Before I tear into the engine again, I'd like to have at least a partial clue as to where I need to go.  Redoing the valves with new seals is perhaps my first step, but would like some input.

I'm also at the same time looking for a 550 engine to rebuild on the bench while I ride and fog for mosquitoes at the same time    I'm also actively considering a 650 - anyone actually ever do this?  We've all talked about how a 650 is apparantly a straight bolt-in to a 550 frame, but I've never actually heard from anyone who's done it.  Any inherent benefits of the 650 engine, aside from displacement increase?

[MRieck]

Does it smoke all the time, just at start up etc?

[Tim.]

Seems to be all the time, and seems to be worse when hot.

[dusterdude]

what about these o-ring issues like the 750`s have?

[clarkjh]

I got to keep an eye on this, I doing mine right now.  When you find the problem please let everyone know so I some one else doesn't have the same problem.

James

[hcritz]

Hey Tintin;
Have you talked with the shop that did the work???
They may check it out for you.
If it's smoking from all cylinders...more than likely a ring issue. installed incorrectly...or sized incorrectly...I've seen them installed upside down...Std rings in overbores...etc.
I've also seen people  crush the valve stem seals with a C-clamp style spring compressor. If it's set wrong you can compress the valve spring retainer into the new seal and destroy them.
Just some thoughts...best to check with the shop first...maybe they will make their work good.

[WHALEMAN]

A simple leak down test will tell a lot. A compression test first dry and then with thick oil in each cylinder will rule rings in or out. I lean towards valve seals on a new rebuild. I remember an old friend used to rebuild old British bikes and he told me how he had to get real cheap single grade junk oil for the first 200 miles because he claimed that with modern oil those old bikes rings would never seat and the cylinders would glaze and they would burn oil forever.

[MRieck]

I've also seen people  crush the valve stem seals with a C-clamp style spring compressor. If it's set wrong you can compress the valve spring retainer into the new seal and destroy them.
.

Boy....you'd really have to crank that down....like to coil bind.

[TwoTired]

A few years ago, I had my Lycoming engine overhauled, air cooled, 4 cylinder.  New pistons rings and cylinder barrels installed.  Break in regimen was to use straight non-detergeant no additive mineral oil for the 25 hrs of operation at 75% of maximum power.  This was primarily to allow the rings to scuff in and seat properly to the cylinder walls.

When the bike was new, it came with a break in oil that was to be changed at 500 miles after break in.

Can you tell us what oil was used during the break in period for your engine?

Cheers,

P.S.
You guys complaining about engine parts for the SOHC4, take note.  Yours are cheap.  My Lycoming was $18,000 dollars to rebuild (not including removal and installation labor) . A four cylinder 360 cubic inch, boxer type, air cooled motor.
Flying is a poor man's hobby.

[MRieck]

A few years ago, I had my Lycoming engine overhauled, air cooled, 4 cylinder.  New pistons rings and cylinder barrels installed.  Break in regimen was to use straight non-detergeant no additive mineral oil for the 25 hrs of operation at 75% of maximum power.  This was primarily to allow the rings to scuff in and seat properly to the cylinder walls.

When the bike was new, it came with a break in oil that was to be changed at 500 miles after break in.

Can you tell us what oil was used during the break in period for your engine?

Cheers,

P.S.
You guys complaining about engine parts for the SOHC4, take note.  Yours are cheap.  My Lycoming was $18,000 dollars to rebuild (not including removal and installation labor) . A four cylinder 360 cubic inch, boxer type, air cooled motor.
Flying is a poor man's hobby.

My sister had some diesel type engine in her sailboat....same in regard to rebuild price.

[Tim.]

Unfortunately I didn't know much about breaking the engine in afterwards - as part of the rebuild, they put new oil in of course, and frankly, I don't recall what they used.  They only work on older bikes, so presumably they used straight up 10-40.

My most recent oils have been Motul 3000+, which I think has some additives.  It was the most basic I could lay my hands on at the time.  Now I'm using Honda 10-40 oil that has no mention of any detergents etc.

I've put close to 2000 miles on the bike since the rebuild.  I'm going to play with my compression tester to see what I can see, and then may take it in for a proper leak-down test.  Should I be doing the compression test warm or cold?

[crazypj]

Has it done this all along?( directly after re-build you were told it would be ok after a few miles?)
One thing I've seen a lot, even with 'experienced' mechanics is the piston rings upside down and in the wrong position ('yea, I fitted the ridge dodger right')
It was really the secondary oil scraper ring
Any marking on rings go to the TOP side.
Top ring has chrome face, second may or may not have a groove in lower surface ( but is always tapered)
And oil ring, if 3 piece, has slight barrel to face,  expander spring fitted, rails after. not sure about one piece ( I forget stuff)
PJ

[clarkjh]

crazypj

I want to get this straight in my head

Top ring - crome face with mark up
Second ring - grove faces down?
One piece oil ring - no mark so doesn't have a top or bottom.

James

[TwoTired]

They only work on older bikes, so presumably they used straight up 10-40.
Now I'm using Honda 10-40 oil that has no mention of any detergents etc.

Unless otherwise stated on the label, I think any multigrade oil is going to have additives and detergeants.  The additives are what makes them mutligrade and they are often added to the base stock oil in a "package" blend with other friction modifiers.

Should I be doing the compression test warm or cold?

The engine should be the same temp as it would be cruising down the highway at 40-60 MPH. (in the ideal case, of course)  This is likely where the heated parts and their indivifual expansion characteristics have reached equilibrium. Things aren't going to fit together any better than at this time.  Unless, of course you have a race engine.  Then you want the engine at the temp reached during WOT.

Cheers,

[lassenc]

http://www.mototuneusa.com/break_in_secrets.htm

I don't know what to think :/

[scunny]

I was told 20 years ago when I asked a top racer how he broke in his bike.
20 laps

[crazypj]

crazypj

I want to get this straight in my head

Top ring - crome face with mark up
Second ring - grove faces down?
One piece oil ring - no mark so doesn't have a top or bottom.

James

Rings are marked either R (regular) S (standard) or the oversize ( 25= 0.25mm, 50= 0.50mm, etc)
second ring, if it has a 'groove' ( more a recess on the bottom) it goes DOWN
 I think the one piece is marked but the 3 piece isnt.
PJ

[clarkjh]

Thanks crazypj

I bought a set of 59mm oversize 500 pistons to put in my 550.  I will post my ebay feedback tomorrow when my machinist looks at the pistons.  Just wanted to make sure that I put them in right.

James

[crazypj]

crazypj

I want to get this straight in my head

Top ring - crome face with mark up
Second ring - grove faces down?
One piece oil ring - no mark so doesn't have a top or bottom.

James

Rings are marked either R (regular) S (standard) or the oversize ( 25= 0.25mm, 50= 0.50mm, etc)
second ring, if it has a 'groove' ( more a recess on the bottom) it goes DOWN
 I think the one piece is marked but the 3 piece isnt.
PJ

Forgot about N=Normal

[Tim.]

Thanks crazypj

I bought a set of 59mm oversize 500 pistons to put in my 550.  I will post my ebay feedback tomorrow when my machinist looks at the pistons.  Just wanted to make sure that I put them in right.

James

Did you buy the set from Classic Cycle Parts?

http://cgi.ebay.ca/Honda-CB500-Four-BIG-BORE-555cc-Performance-Rebuild-Kit_W0QQitemZ4637537680QQcategoryZ35595QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

That's the set I bought - I actually was the one to confirm with them that they were 59mm pistons, and that they'd work on the 550 as a .5mm overbore.  Don't know why they don't market them for the 550 as well as the 500.  The 605cc kit is tempting too - fresh sleeves, but then you're into boring the cylinder block.

http://cgi.ebay.ca/Honda-CB500-Four-BIG-BORE-605cc-Performance-Rebuild-Kit_W0QQitemZ4636941657QQcategoryZ35595QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[crazypj]

550 will bore to 591 with STD. 750 pistons and you dont need to bore block or change liners. The 605 are max OS 750?
PJ

[clarkjh]

Yep, those are the ones.  I thought of getting the 605 kit but didn't really want to pay that much extra for sleaves I wouldn't use.

James

[Tim.]

550 will bore to 591 with STD. 750 pistons and you dont need to bore block or change liners. The 605 are max OS 750?
PJ

What diameter are standard 750 pistons?  They just mount on the existing rods, or do you need 750 rods too?  I wasn't aware that you could drop 750 pistons into the 550.  Might be a next step up if I happen to have to do another rebuild.

I'm sourcing another 550 engine to rebuild on the bench while I ride the mosquito fogger.  I'll get a leakdown test done, and if it looks like the valves, I'll pull them and re-do the seals with new Honda parts.  If it's the cylinders, I'll likely leave things alone and build a new engine and use this lemon as a boat anchor.