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Old 06-13-2012, 05:50 PM   #1
italiano OP
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CARB HELP please

I have a 1978 r 100 s, on the bings i changed the carb diaphrgam and the springs, that was after putting new piston rings. So when i frist start the motorcycle a big cloud of withe smoke was coming out, i thought that was because of the new bad rings. I ask for some advice in a previous tread, so i went over to test and the compression was very good. i start to see that was an enormous amount of gasoline left unburned (white thin smoke)and the spark was very dark.
MY QUESTION IS : Is it possible that the new spring and diaphrgram as raised so much the gasoline that i has to lower the needle two step and i have still to much gas? I am on the lowest step of the needle so i cannot lower that any more.
The motor has around 65000 miles, do you think i have to change the needle and the pre atomizer ?
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Old 06-13-2012, 06:02 PM   #2
patanga
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Quote:
Originally Posted by italiano View Post
I have a 1978 r 100 s, on the bings i changed the carb diaphrgam and the springs, that was after putting new piston rings. So when i frist start the motorcycle a big cloud of withe smoke was coming out, i thought that was because of the new bad rings. I ask for some advice in a previous tread, so i went over to test and the compression was very good. i start to see that was an enormous amount of gasoline left unburned (white thin smoke)and the spark was very dark.
MY QUESTION IS : Is it possible that the new spring and diaphrgram as raised so much the gasoline that i has to lower the needle two step and i have still to much gas? I am on the lowest step of the needle so i cannot lower that any more.
The motor has around 65000 miles, do you think i have to change the needle and the pre atomizer ?
Hi Italiano.. The needle should ideally be on the middle step on all our BM CV Bings.. If the plugs are really black then check your mixtures first. Do you have a carb balancing gauge?... Regards the new rings; Can I presume the same symptom didn't exist prior to fitting the rings?

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patanga screwed with this post 06-15-2012 at 08:55 PM
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Old 06-13-2012, 06:22 PM   #3
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When you put in new rings did you hone the cylinders?
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Old 06-13-2012, 06:27 PM   #4
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The engine idles very good, and i have balanced it with no trouble, today i will try without the air filters. with more air equals less gasoline, so if i get better burn i am too rich.

In the microfice of max bmw the size of the main (if i put the series of my motorcycle) displays 170.
I read on other post that everyone is going with 150 or 160 and i am at 6000 ft above sea level. So i think 150 will be better. do you?
What gives you more gas the main or the position of the float needle? how is called the yet that recives the needle inside?

Thanks PATANGA and DISSTON with this, and yes i honed the cylinder with the lighest stone i could find. I have 130 comp on one cylinder and 132 on the other.
When i mont the valves i redo the seat and i cheq with whater , no leack.
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Old 06-13-2012, 06:31 PM   #5
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Are you sure the oil rings are installed properly?
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Old 06-13-2012, 07:36 PM   #6
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Baloneyskin mentioned my first thought, reversed rings would essentially feed oil into the cylinder.
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Old 06-13-2012, 08:26 PM   #7
disston
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White smoke is oil entering the cylinder. If was too much gas it would be black smoke. You say you have white smoke but want to fix carbs. Which is it?

I don't know if an oil ring can be installed wrong. How's that happen?
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Old 06-13-2012, 08:59 PM   #8
Kai Ju
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[QUOTE=disston;18905970

I don't know if an oil ring can be installed wrong. How's that happen?[/QUOTE

If you install the oil ring upside down it'll scrape oil into the combustion chamber. Whether it fit's upside down into the groove I don't know.
The other possibility is that one of the oil rings, or both, broke and no longer has any tension.
I don't think the OP specified whether it smokes from both or just one side.

Also, FWIW, my '77 R100/7 with 42,000 miles has 160 psi per side so the 130/132 seems low.
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Old 06-13-2012, 09:05 PM   #9
patanga
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Quote:
Originally Posted by disston View Post
White smoke is oil entering the cylinder. If was too much gas it would be black smoke. You say you have white smoke but want to fix carbs. Which is it?

I don't know if an oil ring can be installed wrong. How's that happen?

All of the above: Rings are my first thought.... (As disston said; White smoke is not caused by either over or under fueling)

Most modern rings are marked either with the fitment word 'Top' or have an arrow pointing to the top.. Depending on the oil ring type/design it could be upside down also... You say your compressions are ok, so can we presume that you staggered (spaced) the compression ring gaps correctly around the piston?... What about the compression ring end gaps?? Did you check those in the cylinder prior to fitting? .. Incorrect end gaps (i.e. too close) can lead to damaged rings.

IMHO, that then only leaves rings of the wrong type, or size, or damaged in some way, badly worn or damaged piston ring grooves and or a combination of these... I am assuming that your valve guides are in good order... Did you have your barrels and pistons measured and checked prior to fitting the rings & installation?

Does the white smoke smell oily? (as in burning engine oil)

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patanga screwed with this post 06-15-2012 at 08:56 PM
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Old 06-13-2012, 10:02 PM   #10
italiano OP
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Thanks

I think i will reopen the engine and see whats wrong.
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