Exhaust smoke, oil in one carburetor ?

[Hugues]

Hello everyone,
When I drove home from work today, I suddenly saw a lot of white / blue smoke coming from my exhaust when I was 60 km/h and in 4th.
I stopped and parked the Pinz for a few checks, oil level good, no special noise, no smoke when idling or driving in the 1st, 2nd, 3rd. gear.
So I slowly drove home and tried to reproduce the problem on the last strtech by going 60 km/h and in 4th gear and suddenly a lot of smoke again.
So drove home, turned off the pinz and thought a bit.
As you can see in the video, in my opinion oil comes from the front carburetor, but not from the rear.
So I removed the air inlet and saw oil directly after the air filter.
I think it's oil in the front carburetor, in the back hole, not in the front with the flaps ( sorry, I'm not using the correct words ).
Any idea what to do next?
Can this be a broken piston ring? Or does oil come back from crankcase ventilation if something like that? But why only the front carburetor?
Or is that maybe not oil that i see ?

https://www.youtube.com/watch?v=OGBL2tBnukQ

oil around carb.png (220.92 KiB) Viewed 5531 times

[ChickenPinz]

I'd pull the spark plugs and inspect them. That'll tell you a lot.
When the plugs are out, seize that moment to take a look with your borescope. Don't have one? They're cheap these days.
Still nothing? Compression check.

[Hugues]

So this morning I went to the test drive with the pinz, with the vent hose connected in a bottle as shown below
Short version: I could not reproduce the smoke problem / no oil in the bottle

long version:
- Motor started normally with choke fully pulled
- slight smoke / condensation on the exhaust, engine runs normally when idling
- Wait a little, half push the choke back
- 1st a gear and drive off, nothing unusual
- 2nd, 3rd. Gear, everything normal, almost no smoke
- Almost completely push back the choke
- reach 60 km/h, 4th gear, no smoke
- 5th gear, no smoke, speed approx. 70 km/h
- Let it run until the engine has reached normal temperature, no smoke
-come back home, drive the same street where I had the smoke in the 4th gear yesterday, no problem, no smoke
- come home like a happy camper, the engine runs normally when idling, no smoke
-no oil in the bottle.

I will repeat this test at 10 a.m. to make sure.

If we exclude a damaged piston ring for now, I would like to understand where the oil in the air inlet and carburetor came from yesterday when the vent tube was attached. How does the crankcase ventilation system work normally?
- The vacuum of the engine sucks the gas out of the crankcase ? or is it the pressure in the crankcase that pushes the gas into the vent tube?
- If it is the vacuum of the engine that sucks in the gas, then it is normal that I have no oil in the bottle, right ?
- How can oil get into the air inlet and carburetor through the vent pipe? Is anything clogged? I have greasy residues in the oil filler pipe. Can they clog the ventilation system and instead suck in the vacuum oil from the engine?
- What is between the ventilation pipes shown in red in the second picture? Is there a sleeve around the oil filler pipe to collect the oil droplets in the crankcase gas so that they can fall back into the engine ?

If I knew how these tubes are connected, it would make it easier for me to clean them up.

setup.jpg (224.76 KiB) Viewed 5480 times

oil filler breather tubes.JPG (91.09 KiB) Viewed 5480 times

greasy residue.jpg (204.9 KiB) Viewed 5480 times

[Hugues]

Ok, so I removed the oil filler pipe and the 2 vent hoses connected to it.
Quite a lot of greasy white stuff in the pipes, given some WD-40 and then rinsed with air and a rag.
Good to know how the oil filler pipe is constructed, see picture below, there is a sleeve around with 2 openings below,
The round is where the new oil flows into the engine, and the other bow is the sleeve that is connected to the 2 vent hoses.
So I assume that the goal of the sleeve is to collect the oil droplets from the crankcase gas so that they can fall back into the crankcase.

Then I reassembled everything and did another test drive longer than in the morning to ensure that the engine reached the travel temperature.
I haven't seen any smoke, the engine works normally, performance and noise as usual.

So it seems possible that the oil I saw in the air inlet and in the front carburetor came out of the crankcase ventilation system because its parts were clogged. I will continue to drive the pinz and watch the situation, especially signs of engine oil in the air inlet.

I will order new vent hoses and the seal for the oil filler neck, they are quite worn.

base oil filler tube.jpg (221.02 KiB) Viewed 5470 times

[rmel]

The crankcase is normally under vacuum so you would not be collecting any oil in your bottle.

Under vacuum, if you are pulling oil up into the air intake, that could be getting there due to
oil mist in the crankcase condensing in the intake, likely due to very worn or broken rings. This
goes back to a earlier suggestion to check your compression on each cylinder. Better yet -- if you
have a decent air compressor (or access to one), get a good quality leak down tester, it would
give you a far more accurate measurement as well as intake and exhaust valve sealing.

BTW, how much oil do you typically consume every 1,000 kilometers?

[Hugues]

The crankcase is normally under vacuum so you would not be collecting any oil in your bottle.

Under vacuum, if you are pulling oil up into the air intake, that could be getting there due to
oil mist in the crankcase condensing in the intake, likely due to very worn or broken rings. This
goes back to a earlier suggestion to check your compression on each cylinder. Better yet -- if you
have a decent air compressor (or access to one), get a good quality leak down tester, it would
give you a far more accurate measurement as well as intake and exhaust valve sealing.

BTW, how much oil do you typically consume every 1,000 kilometers?

I will definitely have the compression check.
I changed the oil early Feb and driven about 1'000 km since, I do not notice any significant change in oil level.

[Stumbler]

I rarely go on this site, but I saw your question and here I am ...

There seems to be a lack of direction in your line of problem analysis. You need to look for more symptoms and more issues. The picture of your oil spout looks as if maybe you take a lot of short trips. When you take a lot of short trips, water condensates in the crankcase due to never being hot enough to evaporate it, and mixes with the oil and the oil turns that milky white, as if coolant was mixing with the oil, which we all know can't be the case. So, your pinz needs an oil change badly. That being said, there are many reasons a cloud of bluish white smoke could appear and then disappear. Stuck valve on carb, blockage of something, a random gasket that allows air to pass, or even a severe timing issue. Start with checking the easiest and cheapest items first, then graduate to the more difficult, and finally the expensive.

I would start with inspecting the plugs, and maybe a new set ($8) and then check the vacuum hoses and ensure there are no leaks. Balance the carbs with an air flow meter, it might show you if there's an issue with one carb and not the other, and then visually inspect the path all the way to the exhaust. Check the gaskets under the carbs and the throttle body screws. They come loose. I think someone said use a borescope. They're cheap these days on Amazon for $20 for your iPhone. Check the dizzy (do you have points, electrinic ignition module, or SSI?) and see if there is condensation in there. Blow it out and check the tolerances. It might be that you need valve adjustment too. It's slightly more complicated (takes a few hours by the time you remove covers, work your way through all the cylinders, and then reinstall covers with new gaskets) but costs very little to do.

I've found over the years that by doing all the simple stuff I quite often fix an issue, and if not it usually shows me whatever the issue might be because these engines are really simple.

[Hugues]

I rarely go on this site, but I saw your question and here I am ...

There seems to be a lack of direction in your line of problem analysis. You need to look for more symptoms and more issues. The picture of your oil spout looks as if maybe you take a lot of short trips. When you take a lot of short trips, water condensates in the crankcase due to never being hot enough to evaporate it, and mixes with the oil and the oil turns that milky white, as if coolant was mixing with the oil, which we all know can't be the case. So, your pinz needs an oil change badly. That being said, there are many reasons a cloud of bluish white smoke could appear and then disappear. Stuck valve on carb, blockage of something, a random gasket that allows air to pass, or even a severe timing issue. Start with checking the easiest and cheapest items first, then graduate to the more difficult, and finally the expensive.

I would start with inspecting the plugs, and maybe a new set ($8) and then check the vacuum hoses and ensure there are no leaks. Balance the carbs with an air flow meter, it might show you if there's an issue with one carb and not the other, and then visually inspect the path all the way to the exhaust. Check the gaskets under the carbs and the throttle body screws. They come loose. I think someone said use a borescope. They're cheap these days on Amazon for $20 for your iPhone. Check the dizzy (do you have points, electrinic ignition module, or SSI?) and see if there is condensation in there. Blow it out and check the tolerances. It might be that you need valve adjustment too. It's slightly more complicated (takes a few hours by the time you remove covers, work your way through all the cylinders, and then reinstall covers with new gaskets) but costs very little to do.

I've found over the years that by doing all the simple stuff I quite often fix an issue, and if not it usually shows me whatever the issue might be because these engines are really simple.

Thanks for your input.
I have not seen the smoke anymore since I cleaned the crankcase breather tube and oil filler. It was pretty messy.
Indeed I do mostly short trips these days, but these tubes haven't been cleaned up for quite a while with the previous owner too i guess.
I received my pressure gauge, i will do a compression check to rule out the other things.
thanks

[Hugues]

OK, despite my smoke problem being solved, I went on to measure each cylinders compression as proposed earlier.

I read 120 psi on cylinders 1,2 and 3
and 95-100 on cylinder 4.

Now what's the normal pressure I should find? I can't find it in any of the Pinz manuals.
As a precaution, I repeated measure 4. I also pressed the accelerator pedal beforehand.

The oil I found was in the front carburetor, so for cylinders 1 and 2, so probably not connected to a piston ring.
( I found oil in the air inlet and my crankcase vent pipe was quite clogged, I cleaned it and since I had no smoke in the exhaust ).

But is 95-100 on cylinder 4 a cause for concern? Can this be a measurement error? Or not the right method?
Should I then check the valve adjustment ?

[rmel]

Relative to the other pistons, #4 is low.

Just to make sure we understand how you did the test.....

You want the pressure reading on the 1'st compression cycle, that will
typically read 110 to 120 psi. Then you want the reading after 4 to 5
compression cycles -- the reading should pump up. A reading at 130 psi
or higher is OK. If your below 100 psi after 4 or so cycles you have a
chamber leak. Could be rings or valves. It's all somewhat relative as
readings will vary depending upon a cold or hot engine.

One thing worth checking, if you haven't already -- check your valve
adjustment, each should have a 0.2mm gap when the cam lobe is on
it's heel. You just want to eliminate the possibility of a valve not fully
seated e.g. as the Exhaust will wear into it's seat over time.

[Hugues]

Relative to the other pistons, #4 is low.

Just to make sure we understand how you did the test.....

You want the pressure reading on the 1'st compression cycle, that will
typically read 110 to 120 psi. Then you want the reading after 4 to 5
compression cycles -- the reading should pump up. A reading at 130 psi
or higher is OK. If your below 100 psi after 4 or so cycles you have a
chamber leak. Could be rings or valves. It's all somewhat relative as
readings will vary depending upon a cold or hot engine.

One thing worth checking, if you haven't already -- check your valve
adjustment, each should have a 0.2mm gap when the cam lobe is on
it's heel. You just want to eliminate the possibility of a valve not fully
seated e.g. as the Exhaust will wear into it's seat over time.

Thanks, that helps,
That's the max reading i got after a few compression cycles
Will check the valve adjustment, saw how to do it in the manual, also on YT,
will revert
thanks

[rmel]

After you check the valve gap, if the readings didn't change then
the question will be is 100 psi good enough for now on #4. That
will all depend upon where the leak is. If it's the rings, and you
have good enough power then you might be fine for another season.
If it's an Exhaust valve, well that's a different story. It could end
up with essentially no pressure in #4 and you would end up limping
home on 3 cylinders -- yup, happened to me a number of years
ago but on #2.

The best way to diagnose the problem is a leak down test. You
can stick you ear near the exhaust and oil filler tube an listen
to where the air is venting. You also get a more true reading on
the percent of pressure loss per cylinder. That would be my
recommendation to sort this out.

[Hugues]

Hi guys,
coming back on this thread, i had 90-100 psi compression on cylinder 4, and 120 psi on others when engine hot.

I have adjusted all my valves now to 0.20mm, they were mostly ok, some closer to 0.25-0.30mm, cylinder 4 was quite close to 0.20mm

So I measured again the compression, this time with a cold engine, and starting with cyl. 4.
This time i'm measuring pretty much 120 psi on all cylinders, +/- 5 psi maybe, cylinder 4 is slightly higher than others now.

Should I make another measurement with a warm engine ?
I did have the white smoke again in my air intake this summer, same thing, crankcase breather hose was clogged. Now cleaned, no more smoke.

I do have some blowby out of the oil intake tube, see video below, you guys have the same ?
I'm tempted to open up the engine one of these days and check the rings, would be a good learning exercice for me.

https://www.youtube.com/shorts/_QYg820JGGU

[rmel]

Well 120 psi is a bit on the low end of the range, but OK ...

That said that appears to be a fair amount of blow by.

It would be a good idea to redo your compression when hot -- it should
improve with expanding rings and pistons -- if things are normal.

Again, I'd suggest doing a leak down test, it will provide far better
diagnostics w.r.t. rings or valves. The kits are not that expensive,
but you will need an air compressor.

[Hugues]

Thanks a lot for your feed-back,
I did not know the difference between a compression test and a leak-down test,
I've researched it a bit and now better understand from this page:
https://www.pegasusautoracing.com/docum ... =TECH00137

I do have a compressor so i will order one of these testers and revert here.

thanks