Author Topic: 700 miles on rebuilt lemans engine and possible oil issue  (Read 535 times)

Online amamet

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700 miles on rebuilt lemans engine and possible oil issue
« on: June 24, 2022, 01:41:29 PM »
rebuilt the engine on my 77 lemans approx 700 miles ago. gilardoni cylinders and heads redone.  been noticing the plug on the right has been a bit darker and rich.  im using individual choke levers as opposed to the singular cable and lever style.  runs good, hard to start occasionally from what I assumed is the rich plug, left is a nice brown color.

what's really concerning me is when I look through the spark plug hole and the left is dry and still appears dull grey metal but the right one has a bunch of dark build up on it and appears slightly oily and shiny.  rubbed a tip on it and came out a little oily.

just wondering what I need to do at this point? take heads off and examine pistons unobstuctred? I have an auto zone compression tester I can use incase of bad ring run in
thanks and all help is appreciated
Allen

Offline Old Jock

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #1 on: June 24, 2022, 01:57:18 PM »
I would run a leak down test to see what results I got from both sides.

If that's not possible perhaps a compression test "might" show something

Got one of these remote visual inspection testers to get a better look at the piston?

I wouldn't tear into it just yet.

Have the carbs and fuel enrichers (choke) been overhauled?

Could be on of them is stuck or running rich and that's the problem

I'm not mechanic but had something similar on a Sport that was ring gap stupidity (2 ring gaps lined up perfectly) coupled with a cylinder bore outta spec.

In that case I was getting oil leaks on the bottom end due to presurization and small amounts of oil the throttle bodies.

I've also seen stuck "chokes" I think the carbs enrich the fuel rather than choke the airflow

Wiser heads should be along soon

Online amamet

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #2 on: June 24, 2022, 02:25:29 PM »
carbs are rebuilt, chokes are fully seated. plug threads have a slight sheen to them, a little oil maybe.  its the top of the pistons that are bothering me.  hard to see anything through plug hole but what I do see is a little build up and a possibly shiny, wet surface whereas the left is dry and dull grey metal

Online czakky82

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #3 on: June 24, 2022, 02:30:14 PM »
Accelerator pumps?

Have the carbs been balanced?

Does it have an airbox? Oil in airbox could show worn/issues with rings.

Do you engine brake hard?


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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #3 on: June 24, 2022, 02:30:14 PM »

Offline dxhall

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #4 on: June 24, 2022, 03:29:53 PM »
How did you balance the carbs?

I start by measuring the gap at the bottom of the slide with the butt end of drill bits.

After setting the slides equally with the drill bits, I check balance with a gauge - I use a Harmonizer, but there are lots of others out there.  If the gauge shows imbalance, with the slides set equally, something is wrong.  Most common causes of imbalance are air leaks in the rubber manifold (I once bought a bike with one of the manifolds installed backwards) or poor seating of the valves.  There are obviously other (and more serious) causes of imbalance.

Good luck.  I wouldn’t take it apart without further testing.

Online amamet

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #5 on: June 24, 2022, 03:40:52 PM »
carbs are balanced also with a harmonizer. Runs great. Just curious, how would carb issues lend to a slightly oily, built up  piston top on one side only?

Offline guzzisteve

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #6 on: June 24, 2022, 04:25:38 PM »
One side is seating the rings & one side not yet. I'd keep riding it, using Dino oil not syn. See how it goes. Go to 1500mi and look. There is a difference between carbs & oil seepage. Doesn't sound like fuel.
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Online amamet

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #7 on: June 24, 2022, 04:35:57 PM »
rings not seating was what I was thinking. what do I do about the plug getting fouled though?  im using maxima 4 racing oil 20/50 Dino

Offline moto-uno

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #8 on: June 24, 2022, 04:56:02 PM »
  Shiny dark deposits are usually an oil issue . Without seeing the assembly process , I'm curious
if there's a ring alignment concern or possibly a leak in the head gasket from the oil return hole
into the cylinder ? If it doesn't improve soon , it's a quick head removal and maybe barrels .
Good luck , Peter
Forgot to mention , have you re-torqued the heads yet , that's plenty of mileage since assembly . I've
usually done mine the second time by that mileage .
« Last Edit: June 24, 2022, 04:57:54 PM by moto-uno »

Online amamet

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #9 on: June 24, 2022, 06:13:44 PM »
Retorqued twice. Once at 500 second 50 miles ago. I’ll get new plugs and run it for a while and see what happens. If it persists, how is it alleviated?

Online lucky phil

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #10 on: June 24, 2022, 07:17:45 PM »
rebuilt the engine on my 77 lemans approx 700 miles ago. gilardoni cylinders and heads redone.  been noticing the plug on the right has been a bit darker and rich.  im using individual choke levers as opposed to the singular cable and lever style.  runs good, hard to start occasionally from what I assumed is the rich plug, left is a nice brown color.

what's really concerning me is when I look through the spark plug hole and the left is dry and still appears dull grey metal but the right one has a bunch of dark build up on it and appears slightly oily and shiny.  rubbed a tip on it and came out a little oily.

just wondering what I need to do at this point? take heads off and examine pistons unobstuctred? I have an auto zone compression tester I can use incase of bad ring run in
thanks and all help is appreciated
Allen

Sounds like worrying about nothing to me. A rich mixture will also promote an "oily" look simply because incomplete or poor burning results in excess fuel and some cylinder wash. If it doesn't blow oil smoke on the over run from say 5000 rpm or on WOT and the oil consumption is within reason then forget about it and just ride it. If it does it could just as likely be oil through the guide. There needs to be something wildly wrong with an road engine for any meaningful data to be had from "looking at the plugs" There's a reason racers back in the day used to do "plug chops" at the end of the straight at WOT then push back to the pits, because any running at all after the "chop" made the plug reading a waste of time. Everyone still looks at a road engine and "reads the plugs" though expecting low speed running, running on the choke, idling at traffic lights to provide something meaningful in the way of information.   

Phil 
« Last Edit: June 24, 2022, 07:22:28 PM by lucky phil »
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Online lucky phil

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #11 on: June 24, 2022, 07:21:01 PM »
  Shiny dark deposits are usually an oil issue . Without seeing the assembly process , I'm curious
if there's a ring alignment concern or possibly a leak in the head gasket from the oil return hole
into the cylinder ? If it doesn't improve soon , it's a quick head removal and maybe barrels .
Good luck , Peter
Forgot to mention , have you re-torqued the heads yet , that's plenty of mileage since assembly . I've
usually done mine the second time by that mileage .

If you mean "ring gap alignment" then no. Rings rotate on the piston during running anyway so sometimes the gaps will align just like the stars.

Phil
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Online amamet

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #12 on: June 24, 2022, 08:09:33 PM »
Well this is my first complete rebuild, so yes, I may be worrying too much. I’ve never built an engine before so I’m always “worrying” if I didn’t do something correctly, as in just realizing I never checked the ring gap on the new gilardonis.  I assumed since new I didn’t need to. They may be fine but i should have checked.  But, dry clean piston top with a dry good plug on one side and a slightly oily piston top with a fouled plug leads me to believe the rings in the right didn’t bed in yet or properly.

Offline nc43bsa

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #13 on: June 24, 2022, 08:15:59 PM »
If it were mine, I would verify the float levels are correct.
1990 MilleGT

Online lucky phil

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #14 on: June 24, 2022, 08:43:28 PM »
Well this is my first complete rebuild, so yes, I may be worrying too much. I’ve never built an engine before so I’m always “worrying” if I didn’t do something correctly, as in just realizing I never checked the ring gap on the new gilardonis.  I assumed since new I didn’t need to. They may be fine but i should have checked.  But, dry clean piston top with a dry good plug on one side and a slightly oily piston top with a fouled plug leads me to believe the rings in the right didn’t bed in yet or properly.

Language is important. So now the plug is fouled? Where previously it was "a bit darker". Yes you should have checked the ring gaps, like you should have used soapy water and a nail brush to scrub the cylinders out until a white absorbent towel showed zero colouring when wiped in the bore and you could guarantee all the honing grit was removed. The piston rings will be bedded in within a few hundred klms if all is ok and you haven't been nannying it around and letting it idle for long periods. By all means check the carb float as suggested and probably the r/h choke is returning to the running position completely and the usual stuff but unless it's burning or consuming oil I'd just ride it and enjoy. It's only an old ditch pump engine at the end of the day not a MotoGP engine:)
Taking it out on a quiet stretch of freeway and doing some hard pulls from lowish speeds at WOT in 3rd and 4th gear wouldn't do it any harm now either.

Phil     
« Last Edit: June 24, 2022, 08:52:27 PM by lucky phil »
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Online amamet

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #15 on: June 24, 2022, 08:52:29 PM »
The plugs didn’t  really concern me (they’re not that different from each other and not too dark either) as I’d just go through the carbs and adjust accordingly. It was the oil on the threads that got me to look into the plug hole and see the differences on the piston top. Granted, you can’t see much but what I did see got me thinking and worrying a bit




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« Last Edit: June 24, 2022, 08:54:23 PM by amamet »

Online lucky phil

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #16 on: June 24, 2022, 08:55:29 PM »
The plugs didn’t  really concern me as I’d just go through the carbs and adjust accordingly. It was the oil on the threads that got me to look into the plug hole and see the differences on the piston top. Granted, you can’t see much but what I did see got me thinking and worrying a bit




post image online

You're worrying about nothing in my view. I've seen oily plug threads pulled from new car engines as well and people speculating on why they're oily.

Phil
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Online amamet

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #17 on: June 24, 2022, 09:10:36 PM »
Thx Phil, so I shouldn’t really worry about what I see on the pistons? I just figured it wasn’t a coincidence that the darker plug accompanied the built up piston top.  Especially since it’s still only 700 miles after rebuild?  I need to check my idle jet and needle positions regarding the carbs, it’s stock jetting with Zards and K&N filters. Think it’s running rich up to 1/4 throttle. I moved to the burbs from the sticks so I haven’t been able to open her up for a while. Plus I just got over my clutch hand being repaired. Severed a few tendons from grinding wheel gone awry
-Allen

Online lucky phil

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #18 on: June 24, 2022, 10:58:31 PM »
Thx Phil, so I shouldn’t really worry about what I see on the pistons? I just figured it wasn’t a coincidence that the darker plug accompanied the built up piston top.  Especially since it’s still only 700 miles after rebuild?  I need to check my idle jet and needle positions regarding the carbs, it’s stock jetting with Zards and K&N filters. Think it’s running rich up to 1/4 throttle. I moved to the burbs from the sticks so I haven’t been able to open her up for a while. Plus I just got over my clutch hand being repaired. Severed a few tendons from grinding wheel gone awry
-Allen

No don't worry. Ring seal is all about combustion pressure. Anything that maximises combustion pressure for short durations is what the rings need to seal. Just take the hand repair easy. My work partner in the office 15 years ago had a serious back of the hand injury when his gloved hand got dragged into a compound mitre saw after he switched it off and it was running down. It was very ugly and the surgeon repaired the cut tendons but after about 3 months one of them snapped and retracted up into his forearm. The Surgeon was apologetic and a little taken aback and they ended up having to connect the one tendon to operate his two middle fingers. Apparently for some reason they couldn't reconnect the snapped one. Anyway don't push the recovery too hard and give it plenty of time to heal.

Phil   
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Offline chuck peterson

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #19 on: June 25, 2022, 05:43:21 AM »
rings not seating was what I was thinking. what do I do about the plug getting fouled though?  im using maxima 4 racing oil 20/50 Dino

Try a straightforward 20/50…”racing oil” for break in is a red flag for me…may not be letting the rings work their magic
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Online Stevex

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #20 on: June 25, 2022, 06:10:22 AM »
'Racing' oil is usually so called because of high ZDDP levels, not because it's racing oil.
An example is the oil I use in my LM2, Valvoline Racing VR1.

Steve
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Offline chuck peterson

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #21 on: June 25, 2022, 06:13:57 AM »
Really really hot soapy water bath, several times if need be..strange feeling of applying H2O to a freshly honed metal cylinder …that white towel is a neat rick

Ring end gap always needs measuring before installing..

All 3 ring gaps need to be 120 degrees from each other when marrying the piston/cylinder together…they all rotate around the piston at the same pace when running. I learned it’s a wonderful thing have a machinist check the rods, big/small ends, look for roundness..measurin g the shell bearings, installing the interference fit wrist pins, installing the rings after gapping them, fitting the piston into the cylinder …

And handing you the whole mess where all you have to do is slide it onto the crankcase….torque the rod bolts…torque the cylinder studs…no need to try and install the cylinder onto the rings while the rod/piston is attached to the crank..

This I learned after snapping a ring trying to do it myself and asking for help at the machinists…

“Here, let me do that for you…”




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Online Chuck in Indiana

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #22 on: June 25, 2022, 11:32:02 AM »
Have I mentioned before that carburation problems are generally ignition?  :smiley: I chased an oily plug for years because the bike had a weak coil.
That said.. old Jock said
Quote
I would run a leak down test to see what results I got from both sides.
That is my go to when trouble shooting. As Steve said, it may just be rings on that side not bedding in, but unless you *babied* that newly overhauled engine, :smiley:  they normally bed in right away.
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Online amamet

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Re: 700 miles on rebuilt lemans engine and possible oil issue
« Reply #23 on: June 25, 2022, 03:22:31 PM »
Thx chuck, def didn’t baby the engine. Mike rich built my heads, balanced everything and check the big end bearings for me. He also did the timing for the megacycle cam. Not sure if he checked the ring gap when he had all the parts.   Today I dropped from 60 to 55 for the idle jet and went from middle notch to top,1st notch on the k5 needles. Like I mentioned. Most of my riding lately has been 1/2 throttle and less.  The dark plugs are what got me looking into the plug holes to begin with. It may not be anything but the different appearances bug me…for now. I haven’t noticed any smoke or oil consumption as of yet. I need to put more miles on the bike. Being in the suburbs doesn’t help coming from farmlands where I could take the bike out and flog it immediately
Thx
Allen

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