Cant get full sync

[JTGS850GL]

I wouldn't ride mine that far out of sync but I'm sure that many have been. Left side/right side loading would be pretty off balance at lower throttle openings.

 

[Vesmak]

Next time i get rpms to ~2000-2500 and check it. That pic is idle rpms like 1000. And when keep rpms about 3000 then it was almost fantastico (all in 2mm cap).

 

[JTGS850GL]

Yes, make your adjustment at 2000-2500 and see how it looks.

 

[trippivot]

I can't stop laughing -how about this.... half ball pressure difference for the center cylinders is for what?!? - could it be, half ball is because the carb linkages are progressive ? and the engineers wanted to create even momentum in the crankshaft between the 2 pairs of crank throws? 2 and 3 are 1 lump of weight and 1-4 are the other lump so if you make 1 pair the leader the other will follow more smoothly than making them all equal and relying on flywheel weight to carry momentum / inertia round and round.


BEFORE you waste your time synchronizing the vacuum balance -- here is a tip - if you have every mixture screw all set at the same turns out setting - your bike is already not tuned - every single cylinder has a different fuel / air requirement and you need to find the point where the idle drops at a rich point - and where the idle drops at a lean point - if you cannot get both on a single cylinder stop and correct your intake problem for that individual cylinder. every cylinder of a healthy bike should idle drop rich and idle drop lean - then you set your mixture screw to the middle of the two points - after that you can sync at idle and then again at 3000 rpm - and then... and then... by that point you'll never have to do it again

you can change the exhaust and it will not change your sync -- but if you turn a mixture screw -- it WILL change the sync balance.

 

[Guest]

... if you turn a mixture screw -- it WILL change the sync balance.

Sorry, can't agree with you on that point.

The sync screws will change the mechanical throttle setting, which is what causes the vacuum. Adjusting the mixture screw WILL affect how much power that cylinder will produce, but it will still try to draw the same amount of air through the same throttle restriction, which will result in the same vacuum level.

That said, I do my mixture adjustments with the sync gauges still attached. I will do a sync first, to make sure all the carbs are open enough to contribute to the overall power. (If a carb is closed too far, there is no way you are going to see any change in engine speed by turning the mixture screw.) After all vacuum levels are equal, I will turn a mixture screw IN until the speed drops off a bit, then back up about 1/4 turn. Repeat on the other carbs. Start back with the first carb, make sure that 1/4 turn in still makes a change, continue with the other carbs. The change in engine speed is sometimes audible, but can be easily seen when ALL the vacuum levels drop as the engine speed drops, which is why I leave the gauges attached.

 

[Grimly]

Here..even though its a CBR its still a 4 cylindered inline 4 bike and the principle is exactly the same on a GS with CV carbs. Funny how the Brit inn the video is counting 1 as the right side and 4 as the left side when we Americans go from left to right.


https://www.youtube.com/watch?v=KHGPqP6G9cA

Nothing to do with US v UK - he's simply wrong. Yet, on the run-through when setting it up, he had the numbering right.

 

[60ratrod]

I know that it's there and pretty much just a "Suzuki" thing, I am just curious about the physics behind it and why Suzuki feels it's necessary.

I had a couple of Kawasakis that had crossovers, but they were after the collectors on each side. Cylinders 1 and 2 came together on one side, 3 and 4 came together on the other side, then there was a crossover. I think I have seen that on some Hondas, not sure about Yamahas. Suzuki seems to be the only one that had the crossover before the collector. I think that is what gave them their unique sound, but I can't see where it helped to make any more power.

I synchronized carbs for years before I ever saw that half-ball difference in a Suzuki manual, and I continue to set them all the same.

I think the idea behind Suzuki's method of attaching the crossover what to have the next cylinder in series scavenge from the exhaust pulse of it's counterpart since pretty much all Japanese inline 4 cylinders have a direct sequential firing order(1-2-3-4). so 2 would scavenge from 1, 3 would scavenge from 2, and 4 would scavenge from 3. with at least Kawasaki's crossover forming an H crossover system, all cylinder exhaust pressures and pulses can equalize and scavenge more evenly than with Suzuki's system with the crossover being behind the collectors

 

[Grimly]

1,2,4,3
1,3,4,2

 

[Guest]

since pretty much all Japanese inline 4 cylinders have a direct sequential firing order(1-2-3-4). so 2 would scavenge from 1, 3 would scavenge from 2, and 4

What are you smoking?

 

[Guest]

I think the idea behind Suzuki's method of attaching the crossover what to have the next cylinder in series scavenge from the exhaust pulse of it's counterpart since pretty much all Japanese inline 4 cylinders have a direct sequential firing order(1-2-3-4). so 2 would scavenge from 1, 3 would scavenge from 2, and 4 would scavenge from 3. with at least Kawasaki's crossover forming an H crossover system, all cylinder exhaust pressures and pulses can equalize and scavenge more evenly than with Suzuki's system with the crossover being behind the collectors

Your explaination makes about as much sense as Suzuki's crossover placement.

First of all, the firing order is NOT "direct sequential". Most in-line four cylinder engines are 1-3-4-2, but Suzuki chose to make it 1-2-4-3.
Second, how is "2 going to scavenge from 1" and "4 going to scavenge from 3"? Never mind the firing order, which has 4 firing before 3, the question is because those pairs come together AFTER the crossover, which is only between 2 and 3.

You want better scavenging? Look at Kawasaki's CSR bikes. They had a system that brought 1&4 together into one pipe and 2&3 together into another pipe. Those two pipes then had a crossover near the swingarm pivot. Had a different cadence to it, as each pipe had evenly-spaced beats coming through it.