R65 bing carburator standard idle jet

[Adamastor]

I used carb cleaner on all holes, but... at idle can anyone tell me what is going on? Where does the air come from? If I spray carb cleaner throught the idle jet hole I can see it appear on the center of the carb, but turning th idle mixture screw in or out doesn't seem to affect. Is it supposed to affect this? Or does the mixture screw command another way to let some more fuel go in?  

You should expect this even with the idle mixture screw all the way in because there is a another transfer port not controlled by the idle mixture screw. The idle port and transfer port  are tiny holes almost directly under the butterfly.  Is it possible they have been enlarged.

Very good schematic drawing, Barry, I really wanted to understand how does the circuit work. Things would be much easier if instead of too much fuel, I was getting too little. I will try to block the "transfer ports" and see if the mixture screw blocks or not the fuel passage. If I see no difference in "fuel" flow it wont be working like it should..

[Adamastor]

Just remembered one other thing.. can this be exhaust related? If the left side muffler is clogged and the right one not, could this happen?

[Barry]

It's normal to put a little silicon grease on the O rings to ease fitting but I doubt it would help sealing much and as you say it should be the same for both carbs.

I wouldn't have thought it was exhaust related as a partial blockage of one exhaust would have little effect at low gas flow rates when the carb is operating on the idle circuits.

Going back to your idle mixture screws. Is it just the left side that is screwed all the way in.

[Adamastor]

Yes, the other one is about one turn out. I done that with the normal tuning process, turn the screw all the way in and back out slowly until the revs stop climbing and then back up a bit.
Sergio

[Barry]

OK that confirms a fault with the left carb only. What else is there to check ?

Is the butterfly in the right way up (if you or a PO have taken it out) and centered in the venturi. Hold the carb up to the light to check. There should be no light or at least an even ring of light visible around the edge with the throttle fully closed.

[bruce_launceston]

Okay, once again Barry beat me to it, but I too would check carefully that the butterflys are sealing. Even if they are the right way around and up one may not be sealing as well as the other. I had this problem on my bike and I could not get it to idle slowly when warm.
I had to loosen the tiny screws that lock the butterfly to the shaft, put some pressure on the lever to force the butterfy closed and tap the butterfly with the back of a screwdriver to jiggle it totally shut. keep the pressure on while nipping up the screws.
After getting both butterfys sealing almost light tight I was able to get the carbs balanced beautifully and the idle down to where it should be.
Before this I didn't need the choke either which is a sign that something is not right.

[Adamastor]

hmmm This is an interesting point... I have the carb back on the bike, but I seem to remember, that the butterfly was not completely seated (but just a tiny tiny bit open). I thought this was because of the idle stop screw setting, but you tell me that it is supposed to be completely closed at idle?

This morning I went for a small ride along the river on countryside roads, the BP6ES is holding much better than the BP7ES, but still is getting darker. I took it out to look and it was darker on one side than the other. And a bit oily. Is this another bad sign? Perfectly normal on a break-in in situation?

Regards

[Barry]

Depends on whether the idle stop screw is backed right off in which case it should be completely closed  and as Bruce said "almost light tight". What your really checking for is that it's centered and will close as far as the idle stop screw wants it to go. Very little air is needed at idle so the butterfly needs to be hardly open at all maybe 3/4 of a turn on the idle stop screw.  

Just a thought on the plug being a bit oily. You might be getting excessive oil into the carb via the engine breather.  The breather should be piped to both carb inlets and shouldn't favour one more than the other but I've a feeling that can happen if the hoses are not correctly positioned in the centre of the intake tract. Also the breather could be faulty.

[Adamastor]

I will check both these things tonight... maybe I should block the left side breather vent...

[montmil]

I used carb cleaner on all holes, but... at idle can anyone tell me what is going on? Where does the air come from? If I spray carb cleaner throught the idle jet hole I can see it appear on the center of the carb, but turning th idle mixture screw in or out doesn't seem to affect. Is it supposed to affect this? Or does the mixture screw command another way to let some more fuel go in?  

You should expect this even with the idle mixture screw all the way in because there is a another transfer port not controlled by the idle mixture screw. The idle port and transfer port  are tiny holes almost directly under the butterfly.  Is it possible they have been enlarged.

Barry will confirm, but the carb cutaway view supplied is not a Bing but the operational systems are very similar.   Monte

[Barry]

Yes Monte is correct  [smiley=thumbsup.gif]  It was not actually a Bing CV carb. It's a fairly accurate schematic of how a Bing CV work though and the best diagram I can find to illustrate the idle transfer ports.

[Adamastor]

I have news, some of them good, others not so good:

-> Yesterday at night I re-centered the buttefly, but it wasn't that bad.. mostly centered.
-> Also checked the engine breather tubes, and both seem equaly oiled, so engine has been breathing through them... if too much, I cant really know...
I remembered I have been using a 20w40 automotive oil, maybe it is too light and I should change to 20w50 since the engine is drinking too much oil.. (new rings should justify some of this)

Since I checked both these things at night I could not test them...

Today morning I received two orders I had made, the timing light and a new front light and instruments bracket (I had the bracket for the RT model and it looked really weird).

Engine was not completely hot, but holding idle, I tested the timing light. I didn't manage to see a focused image.
Rotating the bean can I could see the timing marks tab appear or disappear from the hole (and also increase or decrease idle speed), but was not able to fine tune it because I could not read it well.

Is this supposed to be like this? Or does this mean I also need to change the chain? The image should be really sharp?
The timing light is an old style "in-line" timing light.

Bummed because of that timing issue, I decided to change the light bracket, but was not able to finish the job before coming to work...

Oh well...  :-/

[Ed Miller]

Why couldn't you read it?  You should be able to find your timing mark by bumping the motor over with the rear tire.  Then you can smear some white paint (whiteout works) over it and wipe off the excess, leaving the white only in the indention of the mark.  That makes it much easier to see.  It stays white for a long time.

[Adamastor]

Hmmm I might try to paint them a bit, but on a normal engine are they perfectly readable or a bit "shaky"?

[Barry]

There are easier timing marks to read. Ours are a liitle deeper in the hole because of the smaller flywheel/clutch carrier. A spot of white paint is definitely needed and a darkened garage helps.

Having said that the timing marks should not be jumping around much at all. I always prefer to do a static check first to see if there is any difference from one cylinder to the other. You can only do that on points models though.