Inlet balance pipe question
- Thread starter oehlin
- Start date
Thomas aus LAU
Hero member
Normally the connections point upwards. These are connected by a sturdy hose including two clamps.
All connections must be absolutely tight!
The pressure equalization between the two inlets results in better engine running.
Take care that the plastic part for Isolation between inlett and cylinderheat has no cracks and perfect O-rings.
Thomas aus LAU
All connections must be absolutely tight!
The pressure equalization between the two inlets results in better engine running.
Take care that the plastic part for Isolation between inlett and cylinderheat has no cracks and perfect O-rings.
Thomas aus LAU
Dellortoman
Hero member
- Location
- Tasmania, Australia
Does it really? I've sometimes wondered about that.
I've always assumed that connecting the spigots together is just a convenient way of closing them off to atmospheric air (bits of hose are easier to find than rubber caps or plugs). Then some numpty came along, saw it and thought it must be a performance thing. And that rumour soon spread, as rumours do.
Why is pressure equalisation a good thing anyway? On a 360° engine, the inlet tracts must by necessity have different pressures. When one cylinder is on the inlet stroke, it will have some vacuum in the inlet tract. At the same time, the other cylinder is on the power stroke with the inlet valve closed and no vacuum in the inlet tract. So a little bit of fuel mixture will flow through the balance hose from the no vacuum side to the vacuum side. But I seriously doubt that the quantity would be enough to have any effect on engine performance. The amount of gas flow through that little tube would be almost nothing compared to the big lumps of air going through the inlet tract.
I suppose it's possible that it might do something at idle when the carby slides are almost shut and the vacuum is high. Perhaps it could help even out the idle mixtures, but only if the carbs are poorly tuned and out of balance at idle to begin with. If a carby is tuned properly, it doesn't need help from the other one.
GregT
Hero member
- Location
- Christchurch NZ
It may have helped at idle in the days of worn Amal Monoblocs - Particularly chopped Monoblocs on a "tuned" Triumph or BSA.
Just put caps on them.
Just put caps on them.
Tippie
Hero member
- Location
- Dr?bak, Norway
Do the triples with the hose between the carbs run better than the ones with the screws plugging the holes for the vac gauges?
Interesting remark
CLEMTOG
Hero member
"Normally the connections point upwards. These are connected by a sturdy hose including two clamps.
All connections must be absolutely tight!"
I prefer to see them on the bottom, and I think this was stock on my bought new SF1, I have always found the spigot size too large to easily adapt to my vacuum gauge, I had to make up a pair of alloy reducers, from big to small hose for this to work, but very well worth doing, because lots of 750 twins never get any carb balancing other than by eye, and tickover plus cold starting are hugely improved, if set up bang on, how many 750 twins do you see tickover for about 20 seconds and then just stop? answer lots, that is why people at red light are constantly blipping the throttle, I find that annoying and it happens on triples as well. mine will tickover for a fortnight, and no blipping, very satisfying but on a twin this could be detrimental to oil delivery for the cams , so be carefull, plus it will then rev right off the clock!
CLEM
All connections must be absolutely tight!"
I prefer to see them on the bottom, and I think this was stock on my bought new SF1, I have always found the spigot size too large to easily adapt to my vacuum gauge, I had to make up a pair of alloy reducers, from big to small hose for this to work, but very well worth doing, because lots of 750 twins never get any carb balancing other than by eye, and tickover plus cold starting are hugely improved, if set up bang on, how many 750 twins do you see tickover for about 20 seconds and then just stop? answer lots, that is why people at red light are constantly blipping the throttle, I find that annoying and it happens on triples as well. mine will tickover for a fortnight, and no blipping, very satisfying but on a twin this could be detrimental to oil delivery for the cams , so be carefull, plus it will then rev right off the clock!
CLEM
Laverdalothar
Hero member
- Location
- Germany
Well - if any bike (no matter if it is a 750, 1000, 1200 or what ever) stops running when idling for several seconds, there is something wrong, that's for sure. It can be carb related, ignition related, valve adjustment or an air-leak somewhere - all of them make the engine potentially not work as designed.
I agree with Clem (how could I not), that balancing the carbs from time to time gives smoother and better running and a good ideal - IF the other things above are correct before you start balancing! otherwise, you simply mask a different issue.
Years back when I was in California, Richard contacted me who had exactly that issue: bike (after a serious re-build) started well, ran somewhat well and all of a sudden, the engine died with a "poff". You could re-start it right away, just to find the engine cutting out again after some seconds of running.
I asked him how he set the float hights and he confirmed they would all be correct. I asked again, if he has set all 3 carbs to 1,5 turns out on the mixture screw, which he confirmed. I checked the mechanical balance of all 3 carbs and they were absolutely very, very close to each other. No air-leaks to be recognized. I took a small screw driver and found the left carb to be 1 turn out on the mixture screw, the center 1,5 and the right 2 turns out. When I adjusted them all 3 to 1,5 out, the bike ran, but like shit - very rough.
Next thing I checked (which is VERY often forgotten...) was the choke sliders. Guess what? they were all uneven and when the right one was completely closed, the center one was a bit open and the left one twice as much open then the center one...
We adjusted the three to the same level and so that they fully close when choke is disengaged. I started the bike and Richards face was priceless when the bike continued running and running and running...
So - please make sure when you balance the carbs, that this is your LAST operation after checking everything else is in good shape and set to the right adjustments - including the choke sliders...!
@Gerald: If you exchange the left to the right on your bike and turn it 180°, it will point inwards also if the balance connector is pointing downwards. ;-)
I agree with Clem (how could I not), that balancing the carbs from time to time gives smoother and better running and a good ideal - IF the other things above are correct before you start balancing! otherwise, you simply mask a different issue.
Years back when I was in California, Richard contacted me who had exactly that issue: bike (after a serious re-build) started well, ran somewhat well and all of a sudden, the engine died with a "poff". You could re-start it right away, just to find the engine cutting out again after some seconds of running.
I asked him how he set the float hights and he confirmed they would all be correct. I asked again, if he has set all 3 carbs to 1,5 turns out on the mixture screw, which he confirmed. I checked the mechanical balance of all 3 carbs and they were absolutely very, very close to each other. No air-leaks to be recognized. I took a small screw driver and found the left carb to be 1 turn out on the mixture screw, the center 1,5 and the right 2 turns out. When I adjusted them all 3 to 1,5 out, the bike ran, but like shit - very rough.
Next thing I checked (which is VERY often forgotten...) was the choke sliders. Guess what? they were all uneven and when the right one was completely closed, the center one was a bit open and the left one twice as much open then the center one...
We adjusted the three to the same level and so that they fully close when choke is disengaged. I started the bike and Richards face was priceless when the bike continued running and running and running...
So - please make sure when you balance the carbs, that this is your LAST operation after checking everything else is in good shape and set to the right adjustments - including the choke sliders...!
@Gerald: If you exchange the left to the right on your bike and turn it 180°, it will point inwards also if the balance connector is pointing downwards. ;-)
Thomas aus LAU
Hero member
In my experience, the engine runs more smoothly and has more torque in the lower speed range. With the hose connection, the idle speed of my 750s can be set lower to 700 - 750 rpm. This is very important to me, as it significantly improves the braking effect of the engine and also reduces fuel consumption.
Others have shown on a test bench that these improvements occur:
"I tested a vacuum compensation on my Ural Ranger. Before installation, the carburettors were perfectly synchronized. After installation, the idling speed is much smoother and the idling speed can be reduced without any problems Percent (measured with a test bench), the effect decreases at higher speeds. With the same driving style, with the installed vacuum compensation system compared to a non-installed system, fuel savings of up to 10 percent result."
A hose connection between different intake tracts is not uncommon. In addition to many well-known auto sport engines, this was also used by Benelli and Yamaha. See: Yamaha - YICS
I don't have to proselytize on the subject - everyone is the maker of their own fortune.
Thomas aus LAU
Others have shown on a test bench that these improvements occur:
"I tested a vacuum compensation on my Ural Ranger. Before installation, the carburettors were perfectly synchronized. After installation, the idling speed is much smoother and the idling speed can be reduced without any problems Percent (measured with a test bench), the effect decreases at higher speeds. With the same driving style, with the installed vacuum compensation system compared to a non-installed system, fuel savings of up to 10 percent result."
A hose connection between different intake tracts is not uncommon. In addition to many well-known auto sport engines, this was also used by Benelli and Yamaha. See: Yamaha - YICS
I don't have to proselytize on the subject - everyone is the maker of their own fortune.
Thomas aus LAU
CLEMTOG
Hero member
I am never sure about anything these days Gerald, cant be arsed to go and look in the shed at my Egli, but.........
what I will say is that as Piet says, the hose just plugs the spigots, lets face it, in theory anyway, (valve timing excepted) the two inlet valves do not open together, but seperatley in different phases pf crank rotation, the time shared when both inlet valves is open? that will take a man like Cam to calculate (remember we are talking twins here) and anyway in terms of milliseconds, there is no time for unequal pressure to balance both inlets down such a small hose, the theory of the engine is simple to explain (schoolboy, suck squeeze, bang, blow) but complex in its working, slugs of air are shoved around a lot and rely on speed of piston movement to change this from moving to staionary (and getting smaller), both inlet and exhaust valves are open for a short period, at the same time, but the fuel air charge stays where it is needed for the squeeze and then the bang, some of it might go back up the inlet in reverse and more frequently return from the exhaust pipe and port,before it gets expelled, to atmosphere, look at two strokes especially stepped piston types (yuk!) which shouldn't work but do (sort of, Allen sythe anyone?)
CLEM
what I will say is that as Piet says, the hose just plugs the spigots, lets face it, in theory anyway, (valve timing excepted) the two inlet valves do not open together, but seperatley in different phases pf crank rotation, the time shared when both inlet valves is open? that will take a man like Cam to calculate (remember we are talking twins here) and anyway in terms of milliseconds, there is no time for unequal pressure to balance both inlets down such a small hose, the theory of the engine is simple to explain (schoolboy, suck squeeze, bang, blow) but complex in its working, slugs of air are shoved around a lot and rely on speed of piston movement to change this from moving to staionary (and getting smaller), both inlet and exhaust valves are open for a short period, at the same time, but the fuel air charge stays where it is needed for the squeeze and then the bang, some of it might go back up the inlet in reverse and more frequently return from the exhaust pipe and port,before it gets expelled, to atmosphere, look at two strokes especially stepped piston types (yuk!) which shouldn't work but do (sort of, Allen sythe anyone?)
CLEM
Then again, idle at 700 revs isn't doing your big ends any good. The rollers risk skidding on the crankpins rather than..... rolling.In my experience, the engine runs more smoothly and has more torque in the lower speed range. With the hose connection, the idle speed of my 750s can be set lower to 700 - 750 rpm. This is very important to me, as it significantly improves the braking effect of the engine and also reduces fuel consumption.
Others have shown on a test bench that these improvements occur:
"I tested a vacuum compensation on my Ural Ranger. Before installation, the carburettors were perfectly synchronized. After installation, the idling speed is much smoother and the idling speed can be reduced without any problems Percent (measured with a test bench), the effect decreases at higher speeds. With the same driving style, with the installed vacuum compensation system compared to a non-installed system, fuel savings of up to 10 percent result."
A hose connection between different intake tracts is not uncommon. In addition to many well-known auto sport engines, this was also used by Benelli and Yamaha. See: Yamaha - YICS
I don't have to proselytize on the subject - everyone is the maker of their own fortune.
Thomas aus LAU
A low idle isn't good for a roller bottom end.
Paul
Thomas aus LAU
Hero member
I have generally installed the thicker oil pumps with more power and the nonsensical hole for lubricating the primary chain is also closed.
For this I only use Motul 3000 = no problems at all.
Connecting rod bearings above and below have not yet shown any signs of wear and are still within the tolerances even by two bikes >100 k km.
Thomas aus LAU
Dellortoman
Hero member
- Location
- Tasmania, Australia
Ha ha. I'm not sure that your confidence in my arithmetic is justified. But the simple answer is that on a 360° twin, there is no overlap of inlet valves opening on both cylinders. If one is open, the other is closed.
On 180° or 270° there may be some overlap (depending on the camshaft spec). I could spend some time working it out but quite frankly I can't be arsed because there's no real point in doing so. I remain unconvinced that the so-called "balance pipe" does anything other than block off the vacuum inlets, regardless of valve timing.
Thomas aus LAU
Hero member
For over 40 years I have trusted the same woman and always a good mineral oil. Both work fine.
The price including freight is a fair 7.43 EUR per liter.
Only with a high tuned modern engine, I would switch to modern oils like Motul 300 V.
Here the price is significantly higher at 13.30 - 14.00 EUR / liter.
Switching neither woman nor type of oil seems to save money.
Thomas aus LAU
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