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650ss - smoking after rebuild

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Hi

   Just built a 650ss café racer which Im immensely happy with . Starts really easy, yet to perfect a tick-over but the bike sounds eager to go, and no nasty noises with reground crank, new stronger conrods with oil feed holes, new pistons and rings, honed bore, and an upgrade in the oil supply with a 6 start oil pump and plain rocker shafts in place of the scrolled type - all fed off the supply instead of the return.

 The only problem is that there is a bit of smoke on the left pot. I've only done 20 miles since rebuilding but its not properly cleared.  I have a 'period Norton Triumph  manual' which states that the spindles should

    'be  fitted with all flats facing inwards to the centre of the engine' 

This is obviously how I have fitted the spindles but on reading some articles in the forum there are references to fitting the spindles with the flats pointing towards the respective rocker caps (away from the centre of the engine' - claiming this will cause smoking by flooding the head with oil.

 Could anyone clarify what one is correct before I start investigating the cause.

 

Many thanks

 Mark 

 

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Its a pretty easy job with the engine hot to remove the end plates and turn the spindles 180 degrees, as is recommended . See what happens. You could check that the valve chambers are oily enough. If after running in you still have a problem you might consider fitting Commando guides and inlet seals. With the upright engine oil can build up on the inlet side as there is a hump in the middle of the head.The drainage could cope with the low pressure system.. 

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Unfortunately I did this to my 650 because a West Midlands purveyor of Norton parts insisted it was a 'must do' thing. I never did get rid of the smoke as the 650 head can't get the oil away quickly and have reverted to the original set up that works perfectly well. As Robert says, the Commando is tilted which helps get the oil away. In addition, I understand that the drain hole at the rear of the head was enlarged,  as were the chamfers on the cam followers to allow the oil to drain better.

6 start gears don't help either as the extra oil just floods the timing case unless you enlarge the drains from that.

As others have said before, not all mods done at Plumstead were great. Good luck in getting it smokeless. I have some brand new 'Mick Hemmings' inlet guides with seals available that I was going to try, but experience of others with the same issues prompted  me to 'go back to standard', and I'm glad I did.

Regards,  no smoking 650 George 

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Robert / George 

 thanks for the replies.

 I did try turning the spindle 180 on the nearside exhaust an hour ago  but the oil issuing out looks about the same. 

 That is, oozing out of the ends but not really collecting in the valve seating area. The right one by comparison looks slightly less oily but not by much. Maybe the exhaust side is not the source of the problem.

George I did this mod years ago back in the 1980s on my  old 99 - but that reduced oiling problems and smoking.

 Maybe I need to explore further  - or see if the problem goes away as rings bed in etc.

 Thanks for your advice guys - much appreciated

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Hi Mark,

You must have been one of the lucky ones then! 

A bit difficult for you I know as your engine needs running in, but on mine I could get rid of the smoke provided I ran at full throttle! I could do this in top as I had seriously overgeared it. If yours does the same, then it is a useful pointer that the inlet guides are the problem, as manifold vacuum pulls the oil down them. If it still smokes under load, then rings become the primary suspect. 

My new Hemmings guides and seals are available if necessary.

Regards, George. 

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Hi, first thought, are the con-rod oil holes both pointing to the flywheel? Are the rings all the right way up? Upside down they smoke on over-run. My Norton handbook says to run the engine in on Old Oil for 5k miles, using mineral oil. Yes it does work. Not so necessary if you hone the bores first. I would not use any of the modern thin synthetic oils in an old tech engine. I have used EP140 to quieten a noisy engine! If you are sure the engine has been built carefully, then run it in gently, it will only improve with time. I had a Triumph Thunderbird that did over 200k miles in the sixties, so old engines last well. I did 17k miles on an Atlas in 1970 without leaking oil, smoking, or major problems. I do not think one worries so much when one is young. 4500 miles in two weeks, no recovery, did not speak the language. It all worked out OK. Hope you have a good summer on it.

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How good is the condition of the oil pump? If the scavenge side is a bit worn then the 6 speed gears will overload the Pressure Release valve and dump neat oil straight into the cover and then the sump. With all this oil plus that from the conrod bleed holes, the scavenge side of the pump needs to be in top condition to cope.

The conrod bleed holes should face outwards to wash the bores. You need a good set of oil rings to cope with this amount of oil being chucked about. Either 3 or 5 piece oil-control rings.

The first 400 odd 650 Nortons had an issue with smoking bores that was later cured by the fitting of special Twinflex rings.

A mistake that quite a few owners have made, is to buy new plain rocker spindles and fit them in old, tired and worn rockers. Then added a pressurized rocker feed driven by a 6 start oil pump. The result being an oil-flooded head. Changing back to a Low pressure Rocker Feed might help.

Sometimes the reboring of cylinders is too good and gives such a smooth finish the rings do not bed-in properly. Honing a bore can also casue this problem. The pistons and rings need to be given varied forces and work conditions to help with the bedding-in process. Running along at a steady 50mph for 1000 miles does not really help. My rebuilt 650 only stopped smoking after 5000 miles and a Track Day event.

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+1  to Phill's comment, after a fair milage ,a good blast round Brands  a few years ago made all the difference.

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Hello when replacing the. Barrel did you stager the piston rings As if not that's where your trouble is yours Anna j

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You can try. Run the bike for a short time to get some oil up the top.

Disconnect the supply from the timing chest and fit the blanking plug to the gallery.

Run the bike and see if it still smokes. You can run for a couple of miles without oil upstairs and not cause damage.  If no more smoke,its too much oil going up top. If it still smokes,  then it is the rings.

If you find it is too much oil up top, then your choices are either to modify the top end to cope (stem seals , improved drainage etc.) or to limit the amount being supplied.

How you achieve this is up to you. I have heard of owners soldering up the nose of the banjo bolt and drilling a smaller hole, others by clamping the plastic feed tube flat. Recently someone found pieces of wire had been put in the banjo to make a restriction!

Good luck, 

George 

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  Some good advice here and a lot for me to think about.

  I did hone the bores, and rings were staggered to prevent by pass - I have 3 part oil rings which were a pig to seat in the grooves. Stronger con rods were installed that have the holes pointing outwards as required

  I think my next port of call would be to temporarily block the feed to the left rockers as suggested.  I know this can be a fast and effective way of determining if it over oiling (I have had the same problem with my Panther M100 in the past. which proved it to be a valve guide)

 If that's a negative then maybe the rings need bedding in and I will put up with the smoke unless it gets worse as it is only fine on the left side only (at the moment).

If the fault does go down to valve guides I will see if I can whip the head off after the run in as I'm loath to do it at the moment especially as its starting and running so well

As for the pump, is it worn?  Sumping is not nearly as bad as my Norton inter  but if its the scavenge side only I probably wouldn't be fully aware - maybe one to look for but as mentioned its only the left cylinder.

   By the way  - excellent owners club forum and its nice (and helpful) to see so many people wish to impart their knowledge and ideas to assist

Many thanks all

Mark

 

 

 

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Hello now the left hand inlet valve springs are sat on a fiber seal and this is right next to a oil hole drain away for the inlet side now the exhaust side oil runs down the push rods tunnels to feed the cam followers now going back to the inlet side of the valve train this oil hole hose down the back of the cylinder head and down the back of the barrel to the crankcase on the timing side it come out just behind the timing chain and there is a L shape in the crankcase oil way and this is where it gets blocked up mostly with gasket gue so the oil is not getting way and backs up and as no were to go but down the valve guides then gets you thinking its the piston rings or a worn bore .   witch its not ,  and the first 350 650s had. The solid type oil rings then when on to the  five peace oil rings witch my Manxman has fitted these work well it was in march 1961 the twin flex oil rings came in use I have. A spare set and my self I not that fond of them I find the five peace oil rings are good. My Manxman dose not smoke now but it has just needed the get these oil rings in right and beded in And I am still on Standard bores after 60 years ,yours Anna j 

 


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