XS750 Smoking problem

Firstly thanks to all who offered advise, especially Mike Olson &
Kaybear.

I still have the smoking problem. Lots of white smoke, immediately
from startup.
I'll go over what has already been done, and wait for any other
suggestions. I am about to give up and do what I have been avoiding
from the begining. i.e. Give it to a workshop : (

1) Bought the bike (with smoking problem) with 600 km since re-bore &
new 1st oversize pistons & rings.
2) Had a spare cylinder head professionaly done as "my" engineering
shop was not happy with the original work. Replaced the head with the
original pistons/rings (600km).
3) Was not happy with compression, so checked valves which were not
set correctly. Lapped valves, re-shimmed (removed shim stock!!
Kaybear)
I HAVE OPENED AND CLOSED THE MOTOR 4 TIMES. ONE TIMING CHAIN LINK
LEFT.
I'll have to order more. : (

All the above was not wasted, as the compression is now very good and
consistent accross the 3 cylinders.

Problem thru all of the above:-
Immediately from startup, a continuous huge cloud of white smoke comes
out the exhaust. This is when in idle, cold or hot.

I know I have asked this a couple of times, how should I go about
troubleshooting?
What should I do before opening up again!
If I need to replace oil rings, can I get these on their own or must I
get a new set?

Angelo
1979 XS750

 

"I didn't read the original replies but have two guesses. Oil rings
not there

Apologise for not mentioning that.

1) Valve guides measured for wear and found to be OK. Valve oil seals
were replaced before and again in the most recent rebuild. 2 type have
been tried. 1st were rubber around a brass ring, most recent were all
rubber.
Both seemed to fit snuggly.

2) When revving on idle, occational bursts of flame can be seen coming
out the exhaust. Don't know if its a specific cylinder producing the
flame. Have an aftermarket 3-2-1 exhaust.

Any checks/tests that I can do on the oil rings before opening the
motor again?
Oil down spark plug hole does not change compression reading but I
suppose this does not prove that the oil ring is ok?

Thanks Angelo (1979 XS750)

 

If its white smoke sounds more like unburnt fuel, is the carb flooding?
Oil burns to blue smoke.

Adam

 

Adam, are you sure about the colour? I get conflicting views of this ng.
The smoke is definately light/white.
If this does mean fuel, how can I troubleshoot further?
Any ideas?

Angelo (1979 XS750)

 

Rich fuel mixtures burn black smoke. Oil burns whitish/blueish smoke.
Sounds like stuck piston rings.
B

 

Not disagreeing, that rich Burns black
but an unfiring cylinder,er ,see other post, can pump out completely Unburnt
fuel vapour as a white mist.But it will, in those circumstances, be
accompanied by all the symptoms of a non firing cylinder, which would be
even more obvious on a triple.

Probably more likely

Adam

 

Rich fuel mixtures burn black smoke.

Based on all your suggestions/advise, It seems I have an oil ring
problem.
I am sure I have not left them out completely, so stuck or wrong type
could be the cause.
Is it possible to confirm this before "pulling" the head by looking at
the condition of the plugs or by some other method?
I have been changing plugs around so can I clean them (how?) first,
run the motor for a while, cough my lungs out, and then check the
plugs?
What do I look for?
Once I do have the pistons in the open, what do I look for? "Stuck"
should be pretty obvious but what about size/type? Can they be
measured as per compression rings by measuring the gap when placed in
the cylinder?
I remember they are made of curly thin metal ~~~~~, not like others I
have seen in the past. i.e. thick double ring with a series of holes.

Thanks
Angelo


Thanks again
Angelo

 

Based on all the info received so far, I take it that a strip-down to
the pistons is necessary?
No further troubleshooting/tests I can do before stripping?
Can I get oil rings on their own or must I order full sets of rings?
Do these bikes have "scraper" and "expander" oil rings?
How do you check the "expander" rings for fit?
Not that it matters, but I have 2nd oversize pistons and rings fitted.
(I mistakenly quoted 1st in my original post.)

Tks... Angelo (1979 XS750)