1971 engine : a lot of white smoke from exhaust and breather pipe

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kommando said:
If you want more info without tearing into the engine then you need to do a leakdown test, if you have low compression this will tell you where the compression is being lost too.
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Soryy but i dont know what is a leak down test and the way to do it.
Please, explain me.
Piero
 
kommando said:
If you want more info without tearing into the engine then you need to do a leakdown test, if you have low compression this will tell you where the compression is being lost too.
Click to expand...

Pierodn has stated that the left cylinder has zero compression, you do not need a leak-down test to confirm the obvious. A bore scope examination will provide more pertinent information, but the top end has to be removed in any event, it sure isn't going to repair itself.

What happened inside the engine to cause this is the question Pierodn seeks an answer to; given that the engine was relatively fresh, I'll throw out a few possibilities:

1) Insufficient skirt clearance
2) Detonation, caused by an air leak or jetting that was too lean
3) Over revving
4) All of the above

There are, still, a myriad of additional possibilities that would yield to an examination after disassembly; a repair is not optional.
 
A leakdown test is a tool that screws into the head in place of the spark plug, you then use it to send compressed air into the cylinder and the escaping air will tell you where the compression is being lost.

https://mobiloil.com/en/article/car-maintenance/car-maintenance-archive/how-to-do-a-leakdown-test

RS, if Pierodn does not want to tear down his engine yet then its the best next step, if it was myself the head would be off already but I am not Pierodn or got working crystal balls ;) .
 
kommando said:
A leakdown test is a tool that screws into the head in place of the spark plug, you then use it to send compressed air into the cylinder and the escaping air will tell you where the compression is being lost.

https://mobiloil.com/en/article/car-maintenance/car-maintenance-archive/how-to-do-a-leakdown-test

RS, if Pierodn does not want to tear down his engine yet then its the best next step, if it was myself the head would be off already but I am not Pierodn or got working crystal balls ;) .
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Hi.
Sure i will remove head and barrells.
But not now.
First i must finish to set my N15 and remove the head to my Atlas (one cilinder stud was cutted off) and remove head and barrells to my R3.
I cannot do more, i have a job and a family.
Thanks for helping me.
Piero
 
After the oil sprayed out on the 850, what was the level of the oil in the oil tank?
 
kommando said:
If you want more info without tearing into the engine then you need to do a leakdown test, if you have low compression this will tell you where the compression is being lost too.
Click to expand...

Hi.
Compression test on 850 is 130 on the right and 120 on the left.
Piero
 
If the engine is cold, those numbers are acceptable.
If after spraying the oil, the tank was still full, then too much oil must have been in the system to start with. There should have been just a small amount in the sump and lines before the bike was started. Did someone add oil to the tank after the engine had sat for a while and wet sumped.
I always check my oil level when the bike is hot after a ride. I also don't fill the tank to the completely full mark on the dipstick. I try to have the level about half way between the marks on the dip stick. I find if I fill it all of the way to the top mark that the extra leaks out. By keeping it at the half way mark the level stays very consistent and I never have to add oil.
One other thought. Is your chain oiler line off the tank neck still hooked up? If it is I would highly recommend that take the hose off and put a cap on the spigot on the tank. Then use quality spray chain lube. If the oil tank is completely full quite a bit of oil can go through the chain oiler.
 
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htown16 said:
If the engine is cold, those numbers are acceptable.
If after spraying the oil, the tank was still full, then too much oil must have been in the system to start with. There should have been just a small amount in the sump and lines before the bike was started. Did someone add oil to the tank after the engine had sat for a while and wet sumped.
I always check my oil level when the bike is hot after a ride. I also don't fill the tank to the completely full mark on the dipstick. I try to have the level about half way between the marks on the dip stick. I find if I fill it all of the way to the top mark that the extra leaks out. By keeping it at the half way mark the level stays very consistent and I never have to add oil.
One other thought. Is your chain oiler line off the tank neck still hooked up? If it is I would highly recommend that take the hose off and put a cap on the spigot on the tank. Then use quality spray chain lube. If the oil tank is completely full quite a bit of oil can go through the chain oiler.
Click to expand...

Hi.
Compression test was done with engine cold.
Chain oiler is plugged.
From the breather pipe removed from oil tank keep out air with engine started (so it is not blocked and seems it works well).
I have drained all the oil from sump, oil tank and timing.
I replaced with 2 litres only of 20/50 new oil.
To day i will have a ride.
If the oil dont spray i will add 0,200 litres and will ride again.
In case i will add 200 litres more and the more to srrive to 2,8 litres.
The OPS valve has a new spring and shim and piston goes free.
I cannot believe tath the head gasket is leaking between the cylinder and the pushrod tunnel and then the air from the cylinder will pressurize the crankcase and make oil blow out of the breather.
Head and cylinder bases was skimmed flat and i have used a new flammed rings gasket and sure i have not overtight studs and bolts.
Thank you for help.
Piero
 
Hi.
To day i have removed the head of my 1971 Commando.
Valves and guides was good.
The top of the pistons seemed good but ........!!!!!!:
- the right pistons was destroyed around the rings upper the right side of the gudgeon piston pin;
-the liner of the right barrell had two deep dents in the sides of the gudgeon pin.
You have already understand, the right piston had lost the circlip right side (but i have not found neither the left one).
Barrell is to throw, the two dents are too deep.
Pistons was new Hepolite type and circlip was the eyelet type.
Left side piston circlis was well in place.
It is the first time it happened to me and i cannot understand why after 5000 km done.
I will change barrell but the pistons that i have are always Hepolite type with the same eylet circlips.
May be is better, if they works, to use the wire type circlips of the GPM Pistons?.
Thank you.
Piero
 
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Hi.
Hi will replace the barrell with a standard size that will be rebored to + 0,20.
I always rebore with 0,9 cents of clearance.
It sounds good for you this clearance?.
Thanks
Piero
 
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Piero, the eyeletted circlips are not symmetrical, there is a sharp edge and a slightly rounded edge. The circlip MUST be fitted with the sharp edge facing out.
 
dave M said:
Piero, the eyeletted circlips are not symmetrical, there is a sharp edge and a slightly rounded edge. The circlip MUST be fitted with the sharp edge facing out.
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Hi Dave,
is really first time i hear what you say!.
So the damage happened for the wrong circlip side way?.
Now i am aware for my other engines!!!!
Why there is not written in the pistons mounting instructions.
Not at all are mechanics.
Thank you.
Piero
 
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Piero,I am sorry to hear of the expensive damage to your engine.
Dave M is correct about the position of the circlips, another thing to observe when fitting the circlips : it is important NOT to over compress the clips when fitting to the pistons, cheaply made clips can bent at the thinnest part, and deform.

I have also seen teflon buttons used instead of circlips, I have never used this method myself, but it certainly makes sense when it comes to avoiding the kind of damage that you have now.
 
I am always surprised that we don’t see an increased use of gudgeon pin buttons.

Seems like piston circlip failure has always been an issue, so I wonder why the aftermarket industry hasn’t made buttons more commonplace?

1971 engine : a lot of white smoke from exhaust and breather pipe

Is it purely a cost thing?
 
The JCC pistons come with the simple wire circlips which do not work as JCC supplied poor quality ones, but the groove in the piston is profiled to take the wire circlip and so is circular shaped, putting an eyeletted circlip which is designed to fit in a square shaped groove is not the full solution. Now if Wassells are supplying their Hepolite branded pistons made by JCC with eyeletted circlips have they ordered the piston with the matching square groove ? or more likely hoping the eyeletted circlip can cope with a circular groove.

1971 engine : a lot of white smoke from exhaust and breather pipe
 
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Still sounds like detonation destroyed the piston based on the destroyed ring lands . I bet it has 4 corner sieze marks on the skirt. The circlip may have been broken or popped out due to the extreme pounding the piston was undergoing. Unless you determine the cause of the detonation on this bike and your triple you are going to continue to destroy pistons. One of four things is causing this: too hot a plug, too advanced ignition, too lean of a mixture or too low of a grade gas for the compression ration. I don't know what else I can say to convince you of this. It's your bike. If you want to continue to pour time and money into it and have the same result it's up to you. I give up.
 
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