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

Status
Not open for further replies.
Seems you have a massiv leak (blowby) there. The white smoke evading the breather tube appears to be super-hot oil fume, probably because the RH cylinder allows hot combustion gases to enter into the crankcase and hitting the oil sump. The amount of fume corresponds with the leak. The crankcase vent line/tube should be very hot as well. Better not to extend testing any further.

-Knut
 
mdt-son said:
Seems you have a massiv leak (blowby) there. The white smoke evading the breather tube appears to be super-hot oil fume, probably because the RH cylinder allows hot combustion gases to enter into the crankcase and hitting the oil sump. The amount of fume corresponds with the leak. The crankcase vent line/tube should be very hot as well. Better not to extend testing any further.

-Knut
Click to expand...

Hi Knut.
I understand.
But why it happened?.
The bike had not much km. done from new.
Thank you.
Piero
 
Piero, I can only guess here but if we rule out material failure, there *must* be something wrong with the combustion process. This can be caused by too weak A/F (air fuel) ratio, poor fuel (too low octane number), or wrong spark timing, or all of these factors. In short, I bet you had an engine knocking (detonation) incident over some time which hammered (destroyed) your piston.
If so, the evidence will become apparent when you tear down the top end of your engine. I could go into further details here but that would be premature.

http://www.onestopauto.com/What-causes-spark-knock.html
http://www.enginelabs.com/news/detonation-what-causes-it-and-how-to-control-it-using-efi/

I hope these links help. You have my sympathy for having all these problems.

-Knut
 
mdt-son said:
Piero, I can only guess here but if we rule out material failure, there *must* be something wrong with the combustion process. This can be caused by too weak A/F (air fuel) ratio, poor fuel (too low octane number), or wrong spark timing, or all of these factors. In short, I bet you had an engine knocking (detonation) incident over some time which hammered (destroyed) your piston.
If so, the evidence will become apparent when you tear down the top end of your engine. I could go into further details here but that would be premature.

http://www.onestopauto.com/What-causes-spark-knock.html
http://www.enginelabs.com/news/detonation-what-causes-it-and-how-to-control-it-using-efi/

I hope these links help. You have my sympathy for having all these problems.

-Knut
Click to expand...
Hi.
Last saturday we had our bikes feast.
I have invited some friends that have rode seven of the my bikes.
Three of the eight bikes have had problems.
The 71 fastback and 72 R3 same problems of white smoke from silencers and oil tank breather pipe, the 73 850 had a great lost of oil that sprayed from oil return pipe and from oil tank breather pipe.
But the other five bikes have run great.
I have no problem to rebuild the broken engine but i wish to know what happened and why.
Thank you.
Piero
 
peirdon, you mention a recent rebuild. Depending upon the head gasket used, there are rituals to torquing and retorquing a cylinder head until the gasket has beddded in. It seems like you may have a blown head gasket. More dismantle to find out why.
 
Dances with Shrapnel said:
peirdon, you mention a recent rebuild. Depending upon the head gasket used, there are rituals to torquing and retorquing a cylinder head until the gasket has beddded in. It seems like you may have a blown head gasket. More dismantle to find out why.
Click to expand...

Hi.
Bike rebuilt six years ago.
I usually use the flammed ring gasket.
Sorry but i cannot understand what means "blown head gasket" and "gasket bedded in".
Could you explain?
No oil leak from any other parts.
Thanks.
Piero
 
Blown head gasket = head gasket leaking very bad.
Gasket bedded in = clamped as tight as it should be and not tightening any more.
 
pierodn said:
Hi.
The 71 fastback and 72 R3 same problems of white smoke from silencers and oil tank breather pipe, the 73 850 had a great lost of oil that sprayed from oil return pipe and from oil tank breather pipe.
Click to expand...

As for the 71 Fastback I don't believe in a blown gasket. That wouldn't explain the white smoke coming out of the vent line.

With regard to your R3 I think the problem is due to condensation, but please do a compression test when the motor is warm. No angry neighbour poured water into the oil tank I hope!

As for the '73 850 I can only guess at overfilling the oil tank. Maybe oil had drained into the crankcase, the oil tank was topped up assuming oil had been consumed, and upon firing up the engine the oil level in the tank rose to a level exceeding the internal vent line tube? You should drain the crankcase, making sure the oil tank level is coeect, and then verify the oil pump return is delivering the amount it should. if not, oil will accumulate in the crankcase and being fed back through the vent line (assuming you have a reed valve on that engine).

-Knut
 
Numerous replies have encouraged Pierodn to properly warm up the suspect motorcycle by riding it an unspecified distance. Pierodn tells us that he has ridden the "smoker(s)" 36km and/or 60km; not exactly a trip to the center of town; safe to assume that the engines came up to operating temperature, I think the condensation theories don't hold water, so to speak.

A bad cylinder (evidence, observed dynamic compression) especially one with near zero compression would allow raw exhaust gasses, what might burn, into the crankcase, leading to the breather, and also pushing some of this highly burnt oil out of the engine via the exhaust system; last time I checked oil smoke was white.

So Pierodn asks: What could have caused this? Pierodn's collection of motorcycles, the Nortons anyway, have been discussed at length; beautiful machines, rebuilt, restored, customized demonstrating a high level of attention to detail and workmanship; done at the speed of money and with little regard to cost. Very classy.

Pierodn is also a very generous soul, he lets his friends ride with him, on his motorcycles. I suggest that someone missed a shift and cooked the engine(s).

I hope I'm wrong, but the injured hardware was recently freshen up. The work was done to Pierodn's standards, which appear to be well above what the manufacturer was able to do in order to be market competitive. If I'm right it may never come to light (or a reimbursement).

Best wishes!
 
I agree with the above. The bikes were ridden far enough to get up to operating temp. 10km should be more that enough to do that in warm weather. So condensation is not the problem. On start up yes, after riding that far no. Plus the fact it did'nt start until well into the ride.
How were the fastback and Trident running when they started smoking. Any unusual noises.
Just a couple of thoughts. I would work on only one bike at a time and I would start with the Fastback. What you find on that one may give a clue to what is wrong with the Trident. First thing I would do is drain what oil is in the sump and see if there is any metal particles. Can you look at the top of the piston through the plug hole on the cylinder with no compression. Also, is there a automotive repair shop where you live that has a bore scope, a tool used to look inside the cylinder with the head in place. I would see if I could get a look inside to see any damage on the cylinder with no compression. Otherwise pull the head for inspection.
What is happening with the 850 sounds like a different problem. I had something similar happen on a BSA. In that case the oil pickup pipe had plugged and the pump wasn't returning the oil to the tank. Once the sump filled with oil it started coming out in different places and soaked down the rear of the bike including the rear tire. Luckily, I found it in time. It was also fortunate that the sump was full of oil that there was no damage to the bearings as the tank was dry.
I've seen a lot of your posts on here and I know you have the skills to figure this out.
 
Last edited:
mdt-son said:
As for the 71 Fastback I don't believe in a blown gasket. That wouldn't explain the white smoke coming out of the vent line.

With regard to your R3 I think the problem is due to condensation, but please do a compression test when the motor is warm. No angry neighbour poured water into the oil tank I hope!

As for the '73 850 I can only guess at overfilling the oil tank. Maybe oil had drained into the crankcase, the oil tank was topped up assuming oil had been consumed, and upon firing up the engine the oil level in the tank rose to a level exceeding the internal vent line tube? You should drain the crankcase, making sure the oil tank level is coeect, and then verify the oil pump return is delivering the amount it should. if not, oil will accumulate in the crankcase and being fed back through the vent line (assuming you have a reed valve on that engine).

-Knut
Click to expand...

Hi Knut
On 850 i have not a reed valve but inly the stock stell tube from the rear if the timing side.
About oil pump it works fine !!
Thank you.
Piero
 
Hi and thank you for your kindly answer.
RoadScholar said:
Numerous replies have encouraged Pierodn to properly warm up the suspect motorcycle by riding it an unspecified distance. Pierodn tells us that he has ridden the "smoker(s)" 36km and/or 60km; not exactly a trip to the center of town; safe to assume that the engines came up to operating temperature, I think the condensation theories don't hold water, so to speak.

A bad cylinder (evidence, observed dynamic compression) especially one with near zero compression would allow raw exhaust gasses, what might burn, into the crankcase, leading to the breather, and also pushing some of this highly burnt oil out of the engine via the exhaust system; last time I checked oil smoke was white.

So Pierodn asks: What could have caused this? Pierodn's collection of motorcycles, the Nortons anyway, have been discussed at length; beautiful machines, rebuilt, restored, customized demonstrating a high level of attention to detail and workmanship; done at the speed of money and with little regard to cost. Very classy.

Pierodn is also a very generous soul, he lets his friends ride with him, on his motorcycles. I suggest that someone missed a shift and cooked the engine(s).

I hope I'm wrong, but the injured hardware was recently freshen up. The work was done to Pierodn's standards, which appear to be well above what the manufacturer was able to do in order to be market competitive. If I'm right it may never come to light (or a reimbursement).

Best wishes!
Click to expand...

Hi.
Thank you for your kindly answer.
My problem is not to open and rebuild again the engine but understand what it happened and why!.
From 2012 i have rebuit 14 norton twins engine and i have never had such failure so i cannot able to recognize what happen.
If you want you will met me and friends here.
https:/thomasdunstall.blogspot.it/
Piero
 
Check cylinder head temps. If the cylinder producing smoke is running cold, check ignition as probably inefficient combustion going on.
 
htown16 said:
I agree with the above. The bikes were ridden far enough to get up to operating temp. 10km should be more that enough to do that in warm weather. So condensation is not the problem. On start up yes, after riding that far no. Plus the fact it did'nt start until well into the ride.
How were the fastback and Trident running when they started smoking. Any unusual noises.
Just a couple of thoughts. I would work on only one bike at a time and I would start with the Fastback. What you find on that one may give a clue to what is wrong with the Trident. First thing I would do is drain what oil is in the sump and see if there is any metal particles. Can you look at the top of the piston through the plug hole on the cylinder with no compression. Also, is there a automotive repair shop where you live that has a bore scope, a tool used to look inside the cylinder with the head in place. I would see if I could get a look inside to see any damage on the cylinder with no compression. Otherwise pull the head for inspection.
What is happening with the 850 sounds like a different problem. I had something similar happen on a BSA. In that case the oil pickup pipe had plugged and the pump wasn't returning the oil to the tank. Once the sump filled with oil it started coming out in different places and soaked down the rear of the bike including the rear tire. Luckily, I found it in time. It was also fortunate that the sump was full of oil that there was no damage to the bearings as the tank was dry.
I've seen a lot of your posts on here and I know you have the skills to figure this out.
Click to expand...


Thank you for your sugests.
I am not very worried for Fastback or Bsa Rocket 3, if the engine (one piston or ..??) has fault i will replace them.
I am very worried for 850 because the bike run very great without problem but after a few km drove the rear tire is full of oil that spray from return oil tank pipe (you can tight the clip but dont change) and from oil tank breathe pipe.
I dont understand what it happen and iehat i must to do. It Is not an engine fault and oil pump works well, too much oil return in the oil tank.
Other fans here say that could bee the piston rings much clearance that pump into the cranckcase air?.
I really dont know.
Ciao
Piero
 
Last edited:
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.
 
Status
Not open for further replies.
Back
Top