WHERE DID IT GO , IM AM WORRIED

[funky]

Hi everyone I am rather sad and a little angry to say that my engine is smoking again.Its the piston ring gaps Im sure of it... Dont know what to do bar go back to a 650 cc buy new cylinders and pistons kit 75mm scrap the big bore stuff. Gutted

 

[Ed Zornes]

Pull the crankcase breather hose off of the air box to make sure the smoking isn't caused by the crankcase breather filling with oil and pumping it to the air box. My petcocks leaked, partially filled the crankcase with gas, and the crank churning around caused oil/fuel (when I checked the crankcase oil level, nearly 3 quarts of fuel had leaked into the crankcase) to fill the air box via the breather tubes. Pay attention to when it smokes: at idle, most likely from intake valve guide wear, or valve guide seals leaking. If it smokes when you are on the throttle, it more than likely is caused by rings not sealing correctly for some reason or another. Is it smoking from one cylinder more than the other..?

 

[funky]

I have fitted a small filter on the breather theres no pipe going to the air filter box, blocked the breather pipe tubes on the air box . I just did a top end rebuild but the top ring gap was 0.009 over spec , thought i'd get away with it .... should be 0.008 to 0.0016 in the book .....gaps are 0.0025 left and 0.0023 right. I have 707 big bore 78mm piston kit new only done 35 miles plugs are coming out black and oily I took a chance with the ring end gap and as the rings are bedding in im getting blow by blue smoke,a little while its ticking over and a lot more when i rev it , a little more from the left side. oil level has dropped about 3mm.
Fitted new valve stem oil seals too .

 

[Ed Zornes]

I think you made a mistake in explaining your ring end gap. You note that you have 2.5 thousandths and 2.3 thou end gap. Are you really saying you a have 23 thou and 22.5 thou end gap..? That should NOT cause undo smoking. More importantly, when you installed the oil wiper rings, did you stagger the end gaps 90 deg or so, so the oil doesn't blow right past the gap of the thin wiper rings into the combustion chamber....? Your ideal compression ring end gap should be right at .016 16 thou. You can set the thinner oil rings about 10 12 thou, as they do not expand as much when at operating temperature. Again, how much oil do you have in the crank case..?

 

[funky]

Oil is mid way between the min and max marks.

sorry the end gap on the top ring was over by almost 1 thou the other rings are in spec and I stagered the gap on all ring as stated in the book

 

[Ed Zornes]

Just in case you have a mismarked or wrong dipstick, how much oil did you actually put in the crankcase..? Anything more than 2.5 quarts is prone to cause a problem...When you had it apart for the "rebuild" did you have the head vatted or cleaned..? I have seen heads where the return path(s) for oil to drain back into the crankcase was blocked, oil backed up in the head, and was being drawn into the intake past the intake guide seals..

 

[funky]

No I did all the work myself. all oil ways were clear, I put in about 2.5 liters of oil i am using millers running in oil to prevent the bores glazing up.

 

[fredintoon]

Hi funky,
before you do a teardown & rebuild, drain out the break-in oil, refill with no more than 2 litres of 20W50 and burn a couple of tanks-worth of miles on the bike.

 

[funky]

Hi Fredintoon thanks for the response I was thinking the running in oil may be too thin. its Millers Liquid glaze bust SAE 20. what i am using.
I messed about with the carbs and re jetted them to stock but my plugs come back, black and greasy no matter what i do with the Mixture screw, also I turn the idle down real low running, adjust the mixture screw get the sweet spot, and its about a quater turn before the mixture screws bottoms out.
I uped the main due to the engine lagging as i go over 1/4 throttle drop the pilot jet to a 30 from stock which is 47.5 check floats , return mixture to 1 and a half out ,,,,no change ,,,Black sooty plugs oily residue ,,, little smoke on idle ,,, when i rev it more smoke and you can smell that oily smell .
I have only done 35 miles took it easy at first then not over 50 to 60 MPH revs never more than 6k lots of engine breaking made sure oil level was half way between max and min . timming spot on, timimg chain , valve lash , timimg by the book ,,,, back to square one. i will try what you suggested as i dont fancy pulling the engine again to yet anyway ....the engine pulls like a train loads of power ... will get some 20/50 tomorrow ....Cheers

 

[funky]

Its funny I feel like i have let you lot down all the advise and effort

 

[grizld1]

Wow, hope the problem turns out to be simpler than it looks right now! Did you stagger the ring gaps? Recommend you take that filter off your breather line and install a one-way valve. If you beveled the ends of the rings you increased the effective gaps; just debur, don't bevel.

 

[funky]

Yes i staggered the gap as to spec

 

[gggGary]

If I understand; you have straight 20 weight in it? Yeah that ain't gonna stay in the engine. The XS has old time air cooled tolerances needs 40 or 50
(multi) weight.

 

[funky]

Thanks gggGary ..I will get some 20/50 stick a new filter on and see how i get on. i started it this morning and initially no smoke but when it warms right up and you rev it both cylinders give some smoke out. hopefully its that or it may help.

 

[funky]

Ok Update time I have done 250 miles the bike does not smoke at all.Thanks Fredintoon took your advise and it was good advise ... I am using a 20/50 Silkolene for motorbikes much cheaper than Mobil one extended life almost half price.
The oil needed topping up a little the other day when i rode about 100 miles over a two day period but instead of almost a litre it was about a small cup full.
I have ordered my Ramair filters and rejetted the carbs as to the advise of 5Twins Thanks 5Twins your wisdom was and is great I wish I lived near you man I would buy you a meal and a beer ......... plugs look great now ,,,and bike run sweet Thanks to everyone who posted
All the best Funky

 

[Michaelo]

350 miles isn't run in yet, please, please don't change a thing until you've run the engine in. If it was me, I'd be doing another oil dump now Funky,

 

[funky]

Hi Michaelo thanks for the advise i will do an oil change as advised many thanks