classic motorcycle forum
Motorcycle Discussions => British Bikes => Topic started by: Boo on February 13, 2015, 07:19:32 PM
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I have a Triumph Tiger 90, I have just rebuilt the entire engine. I goes well but, On start up it smokes like a train. Now I know all about nortons doing this with wet sumping, but Triumphs just do not behave this way. Compression is good and the oil returns well enough as far as I can see and it does not smoke after a few minutes of running. However, after a rest it will smoke again on start up. If I drain out the sump after running it contains 165 cc's of oil. If it is then left for a week, no more oil fills the sump, so no leakdown . I think the problem may be the pump sucking in air and not oil. Has anyone had this before and if so, what needs to be done. I don't want to go inside and randomly look for clues as it is easier to find out the problem beforehand.
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I've had something similar with a VB Ariel outfit. These also have a plunger pump similar to the Tiger 90. With the Ariel it used to get a minute piece of muck on the non-return ball at base of the pump which would just hold it enough off its sea to cause bother.
The cure was quick and simple with just a wipe over the ball required to clean it but despite flushing out the system, the oil tank and lines etc, it would still do it occasionally yet the 350 NG Ariel I ran beside it never did it. Nor did any other Ariel I ever owned.
Looking back on it possibly the return spring was a little tired and not quite up to it but the message is there. Engines with plunger pumps can still wet sump like any other and drive you nuts doing so.
Cheers,
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sounds like the pump return , the oil is draining back down the return pipe and the rocker feed pipe , after this has drained back there will be no more , reseat the ball ,
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165 ccs sounds a lot just from the rockers and cam chamber.
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how much is normally there ?
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I drained out the sump on my T100 and that too had approx 165 cc. BUT, I drained out the sump after running and again a week later, only a thimble full of oil came out. Once emptied, it does not refill again so leak down does not seem to be the problem, only the ability to scavenge.
Is it possible to have a leak on the scavenge side of the pump and suck in air?
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Short period of smoke after starting ,is usually oil running down exhaust guides while stopped.A flooded sump will produce copious smoke for ages as the oil in the exhaust system burns.On cars ,if the valve seals are worn,there will be a puff of smoke on startup,thicker smoke on revving after prolonged idling.A more viscous oil may be the cure.Some poor oils are thin as water when hot.Regards John.
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All new valves and guides fitted less than 100 miles ago. It smokes on start up only and goes away after a minute or two. If it were guides then it would only smoke a bit and only on overrun and all the time it was running.
I took the oil pump out today, cleaned it to within an inch of it's life and re fitted it. Everything seemed ok, but have not yet started it as I would like the gasket goo to harden first. I also checked the scavenge pipe for leaks by fitting a rubber pipe to it and sucking and blowing through it, no air leaks.
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There is a very simple way to check, run hot then leave an hour and take the exhaust pipes off,and you will see streams of oil down each valve.All aircooled engines have some clearance in the exhaust guides,and unless stem seals are fitted,oil runs down.When the motor is running,exhaust back pressure keeps oil from running down. Consider this-if your car used oil at the same rate as a British bike you would use over a gallon between oil changes,you would have to add a quart of oil each time you filled up with fuel.Which is exactly what we did when I was young."Fill er up,and a quart of oil".to the pump attendant.Do you even bother to check your car oil? I dont.Regards John
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My Tiger 90 does exactly the same thing, rebuilt the engine, re bore new pistons, new valves n guides, Morgo oil pump and engine runs sweetly but from start up it smokes for about 3 minutes then its fine. If I drop the oil from the sump before starting it doesn't smoke, I fitted a new pressure relief unit incase that wasn't sealing properly but no time as yet to check it has made any difference.
Colin
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Just checked my T100 this evening. It is doing the same thing, but nowhere near as bad. It must be something in the air. It's the only logical explanation left as far as I can see. Iv'e tried swearing (profusely), threatening and vallium, neither works so far! I have to set the timing this weekend and will see what happens when it fires up. She should have got a Norton.
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Whats wrong with a bit of smoke?Have you never seen a vintage blower Bentley being driven by a burnt out popstar.More smoke from the exhaust than a sixties band.And it cost"free millyin nicker".If you object to the smell,change to engine oil made for a 2stroke Detroit diesel,it burns with less smoke and a much more pleasant smell.I used to love the smell of all the oil smoke on vintage bike rallies.Regards John.
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There is smoke, and again there is SMOKE! This is can't see the back of the garage smoke. And on a rebuilt motor with all new bits there is no reason why it should do it. Can't come up with a logical reason yet, but am hoping someone here can help. I don't want to take the motor apart without some idea of what to look for. :'(
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Could it be too much oil in the system?
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could be over delivery to top end , is the oil tank standard , try radius the back of the rockers , notch in valve spring lower cup etc , every little helps , this sounds like the oil is draining down when standing from the rest of the motor , fly wheel scrapper ?
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Modern oils are not designed to be burnt.They produce volumes of foul smelling smoke from a tiny amount of oil.Special piston rings,and valve stem seals are required to comply with pollution standards.My cure is to use Castrol CRB40 or Rotella DD40 oil.Note that bikes require special high temp exhaust valve seals,normal car types turn into crumbly bits from the heat.Regards John.
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is this a straight oil ? I run straight 40 in a velo but have never tried in a triumph twin ,
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CRB40 is now called Castrol TectionDD monograde 40 oil.RegardsJohn.
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HI Boo,
When the engine was rebuilt was it rebored?
what brand of pistons were fitted? some of the "new" pistons available have crap rings fitted :(
T90's are also known to suffer from porosity of the cylinders when rebored :o
HTH
John
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Oil tank is standard fitment, feed to rockers is all OK. It is the same crankshaft as came out of the motor and nothing on the bottom end is changed. It has approximately 165 cc of oil in the case when drained out. Can anyone please tell me how much they get out of their sump when it is drained after use. If I drain it just after use it is the same amount as when left or a week or more, so it cannot be draining back down from the system, feed or scavenge.
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Oil tank is standard fitment, feed to rockers is all OK. It is the same crankshaft as came out of the motor and nothing on the bottom end is changed. It has approximately 165 cc of oil in the case when drained out. Can anyone please tell me how much they get out of their sump when it is drained after use. If I drain it just after use it is the same amount as when left or a week or more, so it cannot be draining back down from the system, feed or scavenge.
Pistons are T100 jobs from America, can't remember what make, but were supposedly good ones. If the problem was with the pistons it would smoke permanently and not just on start up. T90 pistons are crap, that's the reason why we had the rebuild and fitted a 500 top end, more choice of quality bits. I need to know how much oil is acceptable in the sump, then why it is not scavenging it.
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is the scavenge pipe damaged , try a small extension on the pipe , maybe 1/8 , if it scavenge some oil why not all , could it be to do with the incress in volume , have you altered the breathing
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Scavenge should not be affected by 500 top end as the 350 is identical, I have checked the scavenge pipe when I removed the pump last week. I connected a rubber tube to the pipe and put my finger over the pump end of the oil passage sucked and blew untill my ears popped. Nothing, not a leak anywhere.
I checked the breather today. I blows and sucks just like any other engine. The breather system is sutch that it cannot be assembled wrong or it would not it or work at all. May try lavishing the whole engine with a plethora of engine breathers in a vain hope that it will do some good. Not holding my breath tho'. :'(
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I vote for valve guide problems. Just because someone put new guides and valves into an engine does not mean it was done right. Even if the valve is a tight fit in the guide, oil can leak between the guide and the head if the guide bore was damaged or scored while it was worked on. Most people don't know that guides should be spotlessly clean before they are driven out of a head or the deposits built up on them plow furrows in the guide bore on it's way out.
At low rpm as during starting and idle and warm-up, a cylinder and rings in good shape should not let oil up into the combustion chamber.
Even if an oil pump is in perfect working order, if the face or gasket it seals against is faulty it can let oil travel between ports, even bad cylinder or head gaskets on some bikes can let oil migrate between places it should not.
"Rebuilt" has as many definitions as there are motorcyclists.
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I agree,some of the characters doing bike work drive the guides from alloy heads cold with a big hammer and punch.Seen plenty of heads ruined by scoring of the guide bore.There s often a considerable pool of oil round the guide due to the angle in the head.Regards John.
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Valve guides were fitted by a chap with more experience than your average vintage bike builder. Everything looks good on the head and the bores, rings pistons etc. The biggest dilemma is, Why does it not smoke after two minutes running? When it is cold it fills the garage with so much smoke that you cannot see the back of the workshop. When warmed up, it hardly smokes at all. If it were guides, then surely it would smoke mostly on over run and not continuously. And why does it smoke less when I drain out the sump? It has to be rings and not valves. but WHY if the pistons, rings and bore are in perfect order does it smoke.
I would still like to ind out how much oil is acceptable in the crank case when the engine is switched off.
The only logical explanation would be that the rings are sticking in the grooves and/or it needs to warm up a little to expand and for the rings to seal properly.
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It does sound like oil is getting into exhaust pipes or combustion chamber.
Are the plugs really dirty/oily.
Can you cut off or block off the oil supply to the head (temporarily), take it for a short ride,
and then see if it smokes on startup next morning when cold.
Drain the sump before starting it.
If no smoke, then its in the top end, if smoke then its somewhere down lower.
Don't forget to reconnect the oil supply to the top end either.
If the ride is quite short, lack of oil won't hurt. Note short ride though.
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Excessive oil in the cylinders will cause the rings to float and pass the oil.The unit 650 manual says any more than 100cc after 5min drainback is too much.Oil does not flow down the exhaust guide when the motor is running due to backpressure in the exhaust system.However the inlet guide is subject to manifold depression,and oil flow is increased.Generally oil going down the intake will burn in the combustion chamber,and cause an oily[but dry] plug with heavy deposits,oil running down the exhaust causes bulk smoke.Sump flooding[not wet sumping] is caused by oil runback from the tank,creates bulk smoke that clears up after about five minutes,and wet black oil may run from the joints in the exhaust,depending how much oil is in the sump.Wet sumping occurs while the motor is running due to oil not returning to the tank,same result but continuous[the motor will cut out due to oiled plug sooner or later.]The Triumph manual has a whole chapter on wet sumping /flooding.Nortons are notorious for flooding after a short time stopped,and owners sometimes fit taps to the feed line.Velocette used a suction operated ball valve .Any failure will cause a seizure.I simply drain the oiltank on mine.Regards John.
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You wouldn't think that going from 4 ozs in the sump to 6 ozs would make a vast smoky difference ?
Especially since he sez that no more drains down if left longer....
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Plugs are oily and black, as expected from burning too much lube. All parts were inspected and fitted very carefully. There is plenty of compression, tere is very little oil going to the top end as I can see it through the clear plastic feed pipe. I have double checked the oil return pipe and there are no leaks. ISTILL need to find out how much oil is in the crank case of a 500 or 350 twin. It seems strange that I have the same in two bikes, yet only one is smoking. Can anyone please help with this?
Meanwhile I am going to ride it and see if it get better or worse. If worse ten I will pull off the top end and have another look at the pistons and rings.
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Could the bores be glazed?
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Fat chance! Only done about 100 miles so far. Not even long enough to do anything. So I will ride it and see what happens. Rode it at the weekend, going really well, but the smoke does seem to be a little less, and not a whiff of smoke when motor is warmed up.