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Discussion Starter #1
Just wanted to echo a few member's sentiments on here. I finally got around to doing the vacuum hose mod and the TPS adjustment that I think Invader introduced us to. Granted everyone's bikes are going to run a little differently (I have an '09), but wowie does the bike run ever so nicely now! Its not a huge drastic difference but it kind of smooths out the rough edges that I found to be quite annoying in a few spots along the power band. The engine vibes are even noticeably different. Still there, but less of a nuisance.

For the vacuum mod, I picked up a piece of hose from the local auto parts store (guy didn't even charge me for such a short piece), and connected the two plugged ports. Accomplished it with a long pair of pliers and a screwdriver without removing anything from the bike. For the TPS adjustment, I bought the sensor adapter from the local dealer for about $20, and adjusted the voltage to the upper limit of the recommended wide open throttle setting.

Very happy so far. Now, I just need to find the last culprit for my instrument buzz. I'm starting to think its the button rattle that some have commented on here about.

Happy riding folks.
 

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The vacuum mod sounds good in theory but it will actually harm performance. Also I should mention there are already bypass screws in the throttle bodies that are designed to balance the vacuum between the throttle bodies without linking the vacuum level between them. See service manual.

Directly connecting the carbs with vacuum line (the vac mod you mention) will actually unbalance them as the Versys engine has an uneven (180/540) firing order. Cyl 2 draws air immediately after cyl 1 where as cyl 1 does not draw air until long after cyl 2 has. As a result cyl 2 will have a higher vacuum level than cyl 1 if you directly connect them.

If it was as easy as connecting a vacuum line between throttle bodies the engineers at Kawasaki would have eliminated the complexity of linking them with a complex arrangement of adjustable vacuum bypass screws that limit the free flow of air between throttle bodies.

The reason we need to sync the throttle bodies is because as the intake valves wear, the level of seal they provide, and consequently the amount of air each cyl draws may change. The amount of air in each cyl affects the intensity of the explosion. This is why a sync should always be done immediately after a valve adjust. Synced throttle bodies will reduce vibration.
 

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Discussion Starter #3
You sound more knowledgeable than I in these matters, so I don't doubt your assessment. However, I've only got about 5k mi on the bike (well before a valve adjust and sync is called for in the service manual) and I could feel quite a noticeable difference by doing the mods. Perhaps that means they weren't properly synced at the factory.. who knows.
 

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Tranquil, try undo the vacuum hose mod while keeping your TPS mod as it is now.

Any difference?
 

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Throttle bodies' vacuum bypass adjustment screw (one per TB) does not allow any air flow between TB's. Vacuum bypass screw simply adjusts volume of extra air drawn over individual TB's throttle valve at idle position to balance both TB's vacuum levels at 1300 rpm idle.

I left the right's TB's screw shut, and adjusted the left TB's screw to balance vacuum at 1300 rpm idle. Right TB's vacuum draw increases significantly over the left TB's as you start opening throttles, then tapers back down close to the left TB's vacuum draw at over 4000 rpm and up. Idle quality and smoothness, throttle response and starting ease all benefit from TB's vacuum balance adjustment, with or without the already added coupler hose. With the TB's vacuum equally balanced at 1300 rpm, the added coupler hose channels an equal rate of vacuum pulse between the two, via the vacuum access fittings which bore is smaller than that of the left TB's IAP sensor fitting. Some Honda 4-stroke parallel twins already have a TB vacuum coupler hose.

A 180-degree crank offers the most uneven firing interval: 180 and 540 degrees. It also gives the lowest pumping losses, as displacement in the crankcase remains roughly constant throughout the cycle. A 360-degree crank gives even firing, but both pistons moving together offers the same mechanical balance as a single.

The 6" long 1/8" ID vacuum hose connecting both TB's also affects IAP sensor signal... Adjusting the TPS to raise voltage output into spec range at WOT which raises TPS output voltage just above idle position spec range, adds fuel at low to mid throttle opening to help cure the lean surge, notably near 2800 rpm. It also affects ignition timing advance.

ECU controlled fuel metering: D-J Method and α-N Method

When the engine load is light like at idling or low speed, the ECU determines the injection quantity by calculating from the throttle vacuum (inlet air pressure sensor output voltage) and engine speed (crankshaft sensor output voltage). This method is called D-J method (low-speed mode). As the engine speed increases, and the engine load turns middle to heavy, the ECU determines the injection quantity by calculating from the throttle opening (throttle sensor output voltage) and the engine speed. This method is called α-N method (high-speed mode).
 

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Discussion Starter #6
Well that was informative.. if not way over my head.. haha.

All I know is.. Middy runs a lot smoother than it used to and the throttle response down low is a lot less jumpy.

Planning to take her for a long ride out to wine country this weekend. Should be a good test of her new settings.

:cheers:
 

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Yeah, I like the positive effects of both mods together a lot too. :thumb:
Performance certainly feels as good with the vacuum hose as well. It still is a very popular mod with the French European ER6/Versys Kawette forum members, where I first discovered it a few years ago. They've also experienced with many different hose configurations including with a T fitting(s) on the IAP sensor hose.

A single 6" (15cm) long, 1/8" (3mm) ID vacuum hose like I have seems to offer the best results. :)
 

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I finally did the vacuum mod...... I really like it!
the engine is much smoother below 5000rpm, great for commuting.
I did the 6'' 1/8'' mod.
thx Invader (again ;) )
 
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