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[Norm]

We have a 1A Interceptor that is going through a bit of oil, last week it did 1600ks and used about 4 litres of oil. It was rebored last year, heads done by Headworks, new valves, not 100% sure what he did with guides, can't remember if he replaced them or not but if he didn't they would have been within spec because Basil knows his stuff but this dam thing continues to go through oil. It doesn't seem to smoke but there is slight wetness in the tip of the left hand muffler. Since the rebore it has probably done a bit over 2000 miles so the rings should have bedded in. The cases have a few leaks but nothing excessive Anybody have any thoughts?

[Mark M]

Norm, my thought is, let me know when you find the answer because mine (1966 Mk1) is a bit thirsty too. Not that bad though! I've fitted a pair of JE pistons which run close tolerances and also valve stem oil seals on the inlets (thought the exhaust valves could do with the benefit). I'm running with unmodified breathers but there is no obvious excess at the end of the breather pipe except a bit of oil mist build up over the rear rim over a long period (say the 6 months of this riding season). It sweats a bit from the barrel bases (may have over done the Welseal on the compression plates) but nothing major. Apart from that, oiltight. I was out on it today,what a great bike! REgards, Mark

[Adrian]

I don't know the set-up on the twin engines, but I took the AVL hybrid engine in to Bullet Whisperer last week for some tuning and a bit of a check up, and he found that I had put the compression rings on in the wrong order, the stepped bottom compression ring that actually helps the scraper rings control the oil was in the top slot, er... not helping to control the oil. The compression had been OK. My engine had been blowing a lot of oil out of the breather, but there was also evidence of it on the piston crown. It had been wet sumping too, with a possible partial blockage to the scavenge pump feed. If your man has done the proper job with the valves and guides that either leaves premature wear of the guides or stems (unlikely if he has used quality parts and fitted them correctly) and the top end has been getting enough oil, or else something is not right with those rings. You don't mention any piston slap, so I'm assuming the pistons aren't worn. I'm also assuming no wet sumping! Regards, A.

[Norm]

From what I remember there was no top or bottom on the compression rings but if there was I would have fitted them that way, new pistons rebored and honed to suit the pistons, the crank breather mods have been done by somebody previously or maybe the factory was doing them by 1967, not sure. I plugged the drill port in the right side case under the base gasket to stop relying on the base gasket to seal that. There is oil leaking from the cases but no where near the amount it is going through. I don't want to fit another set of rings because that is just stabbing in the dark and I'm not convinced it is the problem. On another note I rode my Inter to the meeting last night and I realized I have done over 1000 mile on it in the last couple of weeks, I knew I had been riding it a bit but not that much, I also found 4 broken spokes in the rear wheel for some reason

[Dennis C]

Hi Norm. I had the same thing with my super meteor after its complete rebuild, valves guides rebore pistons etc. It was cured by fitting stem seals.

[Paulk]

Norm, I'm no expert on the Inter (or anything else) but echo Dennis and go for the inlet valve stem seals. I understand the perceived wisdom is not to fit them to the exhaust side. I'd also be tempted to look at a Bunn Breather (or similar) set up. My 2p.

[Bullet Whisperer]

Hi Norm, a long shot but I fixed a wet sumpimg Connie once by changing the timing cover for another one. There was a difference in the layout of the oilways and the one I took off was the wrong type. Also pay very close attention to the oil holes in the timing cover gasket for a good alignment with the holes in the cases and the scavenge hole from the bottom of the timing chest, if applicable. Other than that, is the big metal washer outboard of the timing side bearing doing its' job properly? If the inner race of the timing side bearing is too far along the mainshaft, rather than just about flush with the end [sorry Idon;t remember the exact measurement], oil will pass from the timing chest past the metal washer and inner race and flood into the crankcases. Worth thinking about if all the more usual stuff is found to be ok. Cheers, Paul.

[Mark M]

Norm, it occurs to me your oil consumption amounts to 1 litre per 400 kms which, if my calculations are correct, is over a pint for 250 miles. At that rate of consumption I'm surprised there isn't actual smoke to be seen. Mine isn't that bad but the oil just disappears although really hard revving when stationary shows a little blackish smoke from the drive side. Twins seem to burn from the D/S I've noticed. I'm going to do a few jobs on mine over winter and may try seals on the exhaust valves too. Anyone done valve guide lining or used different valves or guide material? Paul, any suggestions?
REgards, Mark

[Norm]

Tanks everybody plenty of things to think about, any of which could be the cause but at least it was better than the Super Meteor that did the same trip, it used 6 litres of oil lol we will have to pull that one down as soon as I get around to finish putting his other motor together, been sitting here for nearly 12 months now lol.If it was wet sumping Paul, and it probably is as it smokes a bit on start up for about a minute before it clears and then there is only the rare puff from the exhaust on gear changes, even if oil was getting back through the washer I think the scavenge pump could keep up. A Meteor broke the washer in two a couple of years ago and half of it came out through where somebody had broken a section out of the case, I got a new washer, cut it in half and fed it back inside the case, JB Welded it all back in and that is working fine and no sign of that one wet sumping or using excessive oil. Have ordered a new set of rings and will fit stem seals and try again. Thanks again

[tribonnie]

Hello ..... oil consumption can really be only be one of 3 things. Oil leaks, oil out of breather or burning oil. Leaks and breathers problems are easy to checked which leaves burning oil. Oil can only get into the combustion chamber by passing the rings, down guides and through the valves, leaking pushrod seals or porous head castings. Porous casting can be checked with some of the proprietary testing kits. The pushrod seals can be a bit of a problem but if they are leaking it is general for the oil to be blown out rather than sucked into the cylinder. So ... sorry to say that this indicates something in the engine build is not to spec. A number of things it can be. Piston clearance, check the barrels have been bored parallel, it is quite common to grip the barrels by the exposed liner at the bottom of the barrel which produces a tapered bore. Also if you are using aftermarket piston use the suppliers figures (forged pistons in iron barrels have large clearances and I have know companies boring for these have ignored the figures because they "feel" they are to big. Ring fitting and gaps, again if you have aftermarket rings the clearance and fitting or these is often different to OEM workshop manual figures. Oil control and taper (scraper) ring design do vary between supplier. Just because they are not marked top does not mean there is not a top, look for a taper or a step. Valve stem to guide tolerance, valve guide fit (quite uncommon this but I have seen guides fall out when dismantled). There is always a question of valve seals, my view is they are just covering up the problem. In my experience the only answer is to re-check everything and when you have checked, check again. Richard