The 1150 has the bigger jets, the rest don't.
Only set the synch that way on the models with the crossover pipe. The ones before that should all be set the same. That's not it.
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The 1150 has the bigger jets, the rest don't.
Only set the synch that way on the models with the crossover pipe. The ones before that should all be set the same. That's not it.
Steve
GS Whisperer
The '83 550E (the one with the 4-valve head and the siamesed carbs) also had richer jets on the inner cylinders.
What made that one interesting is that in each of the two-barrel carbs, the two main jets were different sizes.
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O
Old guy
Guest
My best guess is since exhaust restriction increases cylinder temps, the inner cylinders are allowed to breath a little easier. On the motors with mixed jetting, they probably needed a little more cooling.
K
Killer2600
Guest
Jetting isn't the only factor in fuel mixture e.g. a vacuum leak will lean out a cylinder even if the jets are all the same size. With that in mind add in that the carb sync across all four from the factory isn't equal.
J
JAG
Guest
I don't know or care if this is right but my understanding is as follows.
The cross-over equalises the exhaust pressure across all of the system. It doesn't matter if this is before 1&2 / 3&4 join or after.
There are two pressure states to consider. The first is the increased pressure of a slug of exhaust gas travelling down the pipe. The second is the pressure during the rest of the cycle. The cross-over equalises this. The effect is subtle.
2&3 pots do run hotter on all air-cooled inline fours. The reason is simply due to less surface contact with the cold ambient air. Balancing cooling as best you can, balancing a bank of four carbs as best you can, and balancing the exhaust system as best you can, combined, results in an engine which runs cleaner. That means lower emissions from a more efficient engine in a hp to hp comparison on engine designs.
The ideal exhaust system will have downtubes (header pipes) of equal length, arranged in such a manner that they all meet at the same point i.e. a 4 into 1 pipe. The cross-over in the later 4 into 2 attempts to create the benefits of a 4 into 1 whilst maintaining the aesthetics of the 4 into 2.
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Thought I'd save you the trouble of replying
The cross-over equalises the exhaust pressure across all of the system. It doesn't matter if this is before 1&2 / 3&4 join or after.
There are two pressure states to consider. The first is the increased pressure of a slug of exhaust gas travelling down the pipe. The second is the pressure during the rest of the cycle. The cross-over equalises this. The effect is subtle.
2&3 pots do run hotter on all air-cooled inline fours. The reason is simply due to less surface contact with the cold ambient air. Balancing cooling as best you can, balancing a bank of four carbs as best you can, and balancing the exhaust system as best you can, combined, results in an engine which runs cleaner. That means lower emissions from a more efficient engine in a hp to hp comparison on engine designs.
The ideal exhaust system will have downtubes (header pipes) of equal length, arranged in such a manner that they all meet at the same point i.e. a 4 into 1 pipe. The cross-over in the later 4 into 2 attempts to create the benefits of a 4 into 1 whilst maintaining the aesthetics of the 4 into 2.
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JAG; said:
Thought I'd save you the trouble of replying
K
Killer2600
Guest
Applying that whole concept would mean the exhaust traveling backwards (up the pipe) and a longer distance till exit would be more efficient i.e. the path to get from the #1 cylinder to the right side outlet.
Not sure if that's a reply for me; but that's true, they don't affect each other. They do however both affect the burn and power contribution of the cylinder.
I don't expect anyone here to accept or understand the explanation I was given and have thus passed on anymore than I expect the amish to accept electricity and wireless communications; but, the explanation I have given explains and ties together alot. Maybe if we ever get a fluid and thermal dynamics version of posplayr here we'll have more believers
At the end of the day, it boils down to the japs made it, it works, and that's all you need to know.
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Steve
GS Whisperer
And maybe you can also accept the fact that not everything they made was perfect?
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K
Killer2600
Guest
And maybe you can also accept the fact that not everything they made was perfect?
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Nothing made by humans is "Perfect" nor is anyones doubt. In hindsight though, I guess what they made was good enough to trust your life on, everything in your stable originates from their corner of the globe. :-\\\
I am open to all logic, if anyone wants to explain a better reason for the extra steel that is the crossover pipe then by all means get down and dirty. Put it all together and lay on all the facts you have.
They started the crossover the same year as they went to CV carbs on most models. I bet it was an attempt to create the illusion that it still had the same throttle response that the earlier bikes with VM carbs had. A little more low end grunt so it feels like the power is coming on quicker, so the aggressive rider won't notice the throttle lag as much. Also a slight bit more efficiency at low RPMs to help with emmisions testing, as emissions was the main driver for the new CV carbs anyway. Maybe the crossover allowed it to run acceptably with slightly leaner carburetor settings.
I guess we will need to talk to the retired Japanese engineers who finalised the designs for these bikes thirty five years ago to know for sure.
I guess we will need to talk to the retired Japanese engineers who finalised the designs for these bikes thirty five years ago to know for sure.
K
Killer2600
Guest
Ok, that's a theory, now tie that all into what we have as fact and all your previous thoughts - Jet sizes being equal among all carbs except for the 1150, an uneven factory carb sync spec, a crossover that joins the inner pipes upstream of the 2-1 that joins the left or right pair. In other words, sell your theory because we aren't going to find the person who came up with the design and even if one of us did find the creator everyone else is still going to be a doubting thomas.
Steve
GS Whisperer
Almost everything. :-k
Although it may wear a name badge that originated "over there", my Wing was built less than 100 miles from me.
Not just assembled, either. The engine blocks were cast in a building just down the road, the transmission gears and cranks were machined next door, the plastic pieces were injection molded on-site. A few things, like tires, suspension bits and gauges, came from other sources, but most of it was actually made "right here" in oHIo.
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Nah, I don't care either way. I only have one bike with a crossover, and it runs just fine with all four carbs set the same. OK power, OK gas mileage. The rest of the bikes without them are the same.
The part about the center cylinders on the eight valve GS getting hot enough to require richer jetting is pure BS.
J
JAG
Guest
Nope you've lost me there.
Imagine a steady state system frozen in time. Measure the pressure in each header at equal distance from the exhaust ports. Disregarding any slug of hot gas, the ideal situation is for the pressure in each tube to be equal. If similar equal flow/pressure characteristics are achieved across the induction, compression and combustion phases, then the engine will be fundamentally balanced. Fine tuning of individual carbs will allow for slight variations in each individual cyclinder.
A multicylinder engine is, in effect, several engines, connected at the crank, running simultaneously. To ensure maximum efficiency of the combined engine arrangement, each individual heat engine (cyclinder assembly) must be closely balanced to the others. If not power is lost as one tries to push the other.
Balancing of the carbs can be achieved in the factory to get a base flow characteristic. Individual carbs are then balanced to each other. Balance across the cylinders can be achieved by machining to set tolerances. Balancing of the exhaust depends upon the pipe design. A 4:1 naturally achieves this if header pipes ate of equal lengths and all join the collector at the same place. For a 4:2 system its more complicated. Some form of balancing pipe / box is required. Where that sits is immaterial as we're talking about baseline pressure not the route of the exhaust gasses.
As I said. Its complete bull**** but I buy into it. In short the balancing pipe is not critical. It may at worse slightly reduces the efficiency of a 4:2 system.
All of mine have crossovers, except maybe the 1000E. I certainly don't care either way. I replaced a worn out exhaust system on my favorite 600 dollar 850G with a pretty nice one off this list. I couldn't get all three of the bolts on the pre-muffler/crossover to line up at the same time, so its only got two installed. I can't believe that it needs any at all.
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Sorry but I'm falling off my chair laughing....I've been building and dynoing race pipes for around 30 years and never heard or tried "balancing the exhaust".
FWIW the crossover pipe is fitted to enable more restrictive(quieter) mufflers to be used as the total system flow is then divided between two outlets.
Successful troll though.....
this will be my only response to this thread.
K
Killer2600
Guest
It not about overheating or being able to run it's just better efficiency. Air cooled V-twins run just fine and have always done so even with the inherent attribute that the rear jug runs hotter than the front.
I can buy into the BS theory on that one, mainly because it throws out many laws of physics.
My only response to this is the same as above.
This however brings us back to the original question, "How important is the exhaust crossover pipe." Reason leads us to believe if the muffler is too restrictive to only have one then the OP can't just axe the crossover as the bikes ability to breath will have been cut in half.
J
JAG
Guest
Thanks... I'll just go change my knickers. Pee'd myself in hysterics.
Well I did say at the start it was bull****.
Well after a career of 125 years designing all manner of pipe system... FWIW, and as a side note, how does more restrictive silences benefit the bike? Are you saying by having a connector pipe the exhaust gases from each combustion cycle passes through both cans? How can this be? What evil wizardry drives such things?
I don't get that. Increasing the volume of the pipe will reduce exhaust pressure and hinder evacuation of the cyclinder. Unless of course the pressure drop is insufficient to cause a problem. But then isn't this sharing of the cans actually the same as "a balanced pipe" i.e. the pressure conditions in each individual exhaust route are common across all cyclinders.
Technicians. Gotta love 'em.
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