Running rich

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Harijsk
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Re: Running rich

Postby Harijsk » Wed Nov 22, 2017 2:26 pm

Floats are new and good. I'm 100% sure it's needles. But the frustrating part is that it's not always malfunctioning.

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Snakeoil
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Re: Running rich

Postby Snakeoil » Wed Nov 22, 2017 6:12 pm

If the floats are hanging up or if they are set improperly, this can cause a very rich mixture. It is equivalent to holding the float down with the tickler. Leaking float needles would have to be very bad to influence the mixture on a running engine. They would have to be gushing. And the carbs would overflow with engine off and petcock open.

If these carbs have an enrichener circuit instead of choke butterflies, the seals could be leaking and causing the rich mixture. Floats sticking could be the problem since you say the problem is intermittent.

What is key here is both jugs run rich. Not normal for 2 carbs to have the same intermittent problem.

UPDATE: I just looked up your carbs. They have dual floats. Very common for that design to hang up. Might be pinched in or spread too far or gaskets are protruding into bowl area.
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Rob
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Re: Running rich

Postby Harijsk » Tue Nov 28, 2017 5:27 am

I ended up buying 32mm Bings on ebay for 200eur, the russian Pekars just suck too much, got the engine running somewhat normal, but still it's inconsistent and skipping a beat and so on. With Mikuni set despite the crappy(lean) mixture I had, it was running like a clock work on low rpm. So, CV is the way to go.
Will report back how it turns out. Just have to wait till they get shipped to me. Hope it's not gonna be too cold in the garage by then.

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Re: Running rich

Postby Harijsk » Sun Dec 10, 2017 3:31 pm

So, installed Bings, Starts like a clockwork.

But now I need a confirmation.

When I rev up and then let it idle, rpms are a bit slow to go back down, plugs are whitish, thus everything points to a lean mixture.
Pilot screw is out 4 turns (which is a lot I think), this means I should be sizing up the pilot jet?

Pic of this particular Bing cross section.
Image

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Lmo
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Re: Running rich

Postby Lmo » Sun Dec 10, 2017 7:05 pm

When my /5 is slow to return to idle it is usually time to synchronize them (done hot). Also check; that the chokes are fully closed, and that there is
cable slack at the butterfly arms. Wore old throttle cables can also cause this.

If you load the engine (by letting out the clutch) and the engine idle returns to a "normal" ( 850-1000 rpm for BMW) it is more than likely a timing issue (mech advance on the BMW). If the idle comes down and creeps back up it's usually an air leak. Keep in mind that the throttle stops and idle mixture screws are dependent on each other, and not necessarily the same settings for right and left side. LOTS of variables on the BINGS.

Pre-1973 carbs are junk, and notoriously difficult to tune. What is the number on the side plates of each carburetor?

Pray that the numbers are, 64/32/9 and 64/32/10. If they end in /3 or /4.... . you're going to have problems.

READ THIS NOW > http://bmwmotorcycletech.info/earlybingR75CV.htm

edit - ANDTHESE
http://bmwmotorcycletech.info/bingcv.htm
http://bmwmotorcycletech.info/synchcarbs.htm

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Lew Morris
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1963 (?) Dnural w/ '06 Ural Drive Train
C5 Power Arc
125/42 jets
Drilled slides/
.030" shims

1973 BMW R75/5 (original owner)
1947 HD FL (long gone, forever regretful)

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Snakeoil
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Re: Running rich

Postby Snakeoil » Sun Dec 10, 2017 7:19 pm

Looking at your cross section, it would appear that the idle mixture is a fuel screw and not an air screw. I say that because the passage from the jet goes to the screw rather that into the throat of the carb. But I also see a small air passage going toward the screw. Your drawn in arrow obliterates the detail. However, the Bing info I could find on-line says it is an air screw. But that may not be info applicable to your carbs. A lot of the Bing info on line is for Rotax engines in aircraft. I've never had to monkey with the Bings on my R100/7 so cannot be sure which it is.

Your info says the idle mixture is out 4 turns, which is way too much. If it is an air screw, that would make it lean. Bringing it closer to 1-1/2 turns would richen it up. If it is a fuel screw, then four turns out says the jet is too small. But I suspect that at 4 turns, the screw has stopped having an effect and the size of the pilot is controlling the mixture.

There is lots of info on Bings on the web. If you can work up the energy and patience to read thru all of Snowbum's articles on Bings, you should be well equipped to solve any problem. Only problem with his website is it is little more than an unorganized rambling on a given subject, with no logical arrangement of the info presented. It's like the guy does a hit of speed and then starts typing. But he knows his stuff and the info you need is normally there if you can read thru all the stuff he types to find it. I imagine his English teachers in school had a love/hate relationship with him.

When I hit send, the post would not go. I see that Lew was posting at the same time and he had provided the links to Snowbum's website. Get comfy before you start reading. :wink:
Regards,
Rob
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Re: Running rich

Postby Harijsk » Sun Dec 10, 2017 7:32 pm

Mine are 64/32/367 and 368.

Must say today I have noticed a high pitch metallic sound coming from the engine, which kinda sounds like pinging/detonation, which in turn can be caused by ignition being too early(google says that), gonna try retarding it tomorrow. (I've managed to f*** up the electric ignition thus adjusting it by the book to at most precision is out of the question :( )
It also loses power at higher rpm, but gonna attend to that after it's running fine at lower range (I'm 100% sure it's all about the carbs and maybe ignition timing and tiny bit valves, gonna recheck 'em in the upcoming days)

Snakeoil, I've been reading the trough forums and learned quite a bit. (btw I read almost all of the Snowbum's info on bings while I was waiting for them to be shipped, quite useful site)
Before seeing the cross section of the carb, I was adjusting the screw other way around(shamed myself too for being ignorant :D ), at least today I got it running better than before.
Now I'm contemplating on whether to drill the jet one size up or fiddle with something else.

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Re: Running rich

Postby Lmo » Mon Dec 11, 2017 6:33 pm

Now I'm contemplating on whether to drill the jet one size up or fiddle with something else.


I'm not finding the 367/368 series, so I strongly suggest that you contact BING before whacking on expensive metal parts. Order the CV manual, you're shooting in the dark if you just start drilling things out.

http://www.bingcarburetor.com/cv-motorcycle.html

Remember my comment about the idle mixture screw working in concert the the throttle stop screw. Set your idle mixture screws at the recommended 1.25-1.5 turns out from soft-seat, then work on the throttle stops to get it idling.

edit
Chris Harris video
Lew Morris
Pismo Beach, California, 93449.
1963 (?) Dnural w/ '06 Ural Drive Train
C5 Power Arc
125/42 jets
Drilled slides/
.030" shims

1973 BMW R75/5 (original owner)
1947 HD FL (long gone, forever regretful)

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Mr Wazzock
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Re: Running rich

Postby Mr Wazzock » Mon Dec 11, 2017 7:03 pm

Harijsk wrote:When I rev up and then let it idle, rpms are a bit slow to go back down, plugs are whitish, thus everything points to a lean mixture.


I had this on my R80, turned out I hadn't turned the idle screws out far enough so had to stop it dying at idle by upping the throttgle stops more, this meant too much air so for example no engine braking when I shut off.

Screwed out the idle screws some more (manual said 1.5 turns, BUT as a place to start from, not the final value), this meant throttle stops could come down and normal service was resumed.

Before you go drilling things I suspect your idle jets might (I say might) be partially blocked with hard deposits, this is the trouble with modern gas it isn't made to be compatible with carbs any more, and when it evaporates there's always a "fall-out" of hard crud to block up jets and galleries. Guess how I know.

HTH
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Harijsk
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Re: Running rich

Postby Harijsk » Mon Dec 11, 2017 8:50 pm

Update.
Btw if I hadn't mentioned this before, engine had an overhaul prior to this and have been running for maybe few hours in total since.
At this point I warmed it up, did few rounds around the garage, no more than second gear and maybe 40km/h and parked it back in the garage and it was near to heat seizure(is it called?,engine was really hard to turn around with the kick starter, until it cooled down), this is another reason I think it's too lean.

Judging by the video just posted here, Idle mixture screw does more than increase the fuel bypass trough the pilot jet?
At this point I'm a bit contradicted now, some say that pilot jet and screw is all about 1/4 of the throttle(is it cruising speed), but judging by the video, it's all about the idle?

Gonna check temperature of both cylinders while idling - will they overheat without actually riding and/or revving up.

Here are videos of the engine running with the carbs.

Startup and revving.
Unfortunately you can't hear it dying at higher revs, but it feels like it lacks power when WOTing it.

In this video I think I can hear the ping, meaning too advanced ignition or mixture too lean.


And yes, ordered drill bits from China in various sizes, received completely different sizes, even some magical half size drill :D
So no drilling today.

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Re: Running rich

Postby Mr Wazzock » Mon Dec 11, 2017 8:57 pm

What are you going to drill? Never heard of drilling out jets to make them bigger, normally just buy the different sizes you want? Suppose you needed to revert back afterwards? :o


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Re: Running rich

Postby Mr Wazzock » Mon Dec 11, 2017 9:02 pm

After this ride around and nearly seizing up, what is the color of the spark plugs? If very pale or white then yes suggests too lean.

Have to confess I cannot hear anything that I could say is definitely not right in either of the videos.

Apart from the reluctance to return to idle speed, I agree with that.


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Re: Running rich

Postby Harijsk » Mon Dec 11, 2017 9:10 pm

Mr Wazzock wrote:What are you going to drill? Never heard of drilling out jets to make them bigger, normally just buy the different sizes you want? Suppose you needed to revert back afterwards? :o
-

Increasing(drilling) the diameter by few 0.1mm is gonna be cheaper than buying a set of jets in various sizes, and I can always buy the size I have now, but since this is an unusual situation, I'm gonna just have to fiddle around, just want to be informed as much as possible before I do anything that can't be reverted with a turn of a screw.


Pic of the spark plug after I parked and it was like about to seize.(Keep in mind that the black residue all around is because of running rich with the previous carbs)
Mt10_plug.JPG
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Mr Wazzock
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Re: Running rich

Postby Mr Wazzock » Mon Dec 11, 2017 9:18 pm

Harijsk wrote:Judging by the video just posted here, Idle mixture screw does more than increase the fuel bypass trough the pilot jet?

True, it's fuel & air mixed.

At this point I'm a bit contradicted now, some say that pilot jet and screw is all about 1/4 of the throttle(is it cruising speed), but judging by the video, it's all about the idle?

Not as cut & dried as that, there's a large amount of overlap between what the idle & main jets do.

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Re: Running rich

Postby Mr Wazzock » Mon Dec 11, 2017 9:24 pm

Harijsk wrote:Pic of the spark plug after I parked and it was like about to seize.(Keep in mind that the black residue all around is because of running rich with the previous carbs)
Mt10_plug.JPG


Well if photo is accurate does look quite white. Should be like a light gray sort of color.


Sorry I'm still hung up on this drilling, as an initial step you could use a small drill to clean the jets out, or make sure they are clean, just in case it's just deposits in there constricting them.

I would also want to strip the carburettors & check them out, may need an overhaul. I'm guessing they are used items?


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