I just tried out this new vacuum hose mod that smooths out the low end, which I got from the french Kawette forum: http://www.kawette.net/forum/viewtopic.php?t=19314
The IAP (Inlet Air Pressure) sensor has a hose on the left throttle body. The mod consists of a hose that connects both TB's at the carb synch fittings with the IAP hose coupled to the connector hose. This smooths out the IAP reading and balances out the vacuum pulse between the two TB's. Kawette forum got the idea from an Italian source, and they tried two other connecting methods with additional routes but with the same results... A smoother response at low rpm range without hiccups is noticed, as well as improved tractability, torque and throttle control. Some reported better fuel economy. Engine braking also seems to be reduced.
I really like the improvement so far. :thumb:
UPDATE: (post # 134 on page 7) After noticing that the IAP sensor fitting bore is larger than the two TB vacuum access fittings, I tried connecting the left tube on the smaller vacuum access fitting instead of on the IAP fitting, still with a T and the right tube on the other TB's vacuum access fitting. I had to raise idle rpm back up and it ran very poorly and sounded erratic. I pulled over and quickly put it back like I had it with the left hose on the TB's IAP fitting... I then put the IAP hose back on its fitting and connected both TB's without the T. It's also known as configuration '1' in the french forum, as some have reverted to. It runs at least as well now as with the left hose on IAP fitting and a T like I had it. I'd like to try out configuration '2' now, as shown in second pic... I had enough 5/32" (3.83 mm) vacuum hose to replace the thin, slightly short and bent IAP 6 mm hose as well. I was able to do it all in a few minutes with a slim pair of needle nose pliers.
The best and most simple configuration #1, with a single 6" (15 cm) long 1/8 or 5/32" (3mm) ID vacuum hose on both TB vacuum ports. Leave the left outer IAP hose alone, and forget about using a T:
This is an older thread, but I just did the vacuum hose mod this morning.
WOW... I can not believe how much smoother the bike is at lower speeds. I had my doubts that I could notice a difference, but it is so much smoother especially 1st and 2nd gears that it almost seems like a different bike.
Sounds like the same bike, but reacts differently. And, YES, it SEEMS, or it APPEARS that engine braking is reduced. I know, I know, it cannot be, but all indications are IT IS AS THOUGH engine braking is reduced.
Great mod, it is staying on this bike.
Now what's this I hear about "sub throttle plate" and "PAIR" valve ?
I'm waiting for someone around my area that knows how to do all this stuff to advertise a little business. I'd pay a fair fee to have all these little mods done at once. I'm not much the tinkerer...Besides, mine is more than acceptable, as is. Then, again, better is always better.
Thanks for providing info on sub throttle. I truly appreciate it and learned something new this evening. Don't know that I need nor want to attack this mod at this time.
My next big task is my 44T rear sprocket coming this week.
I went out again tonight like I usually do, on my usual night romp of about 40 miles. I can definitely notice the difference in bike response in the first three gears - and it is GREAT. Where I notice the most is when I need to really slow down for some 90 degree turns on the hilly country roads where I need to accelerate as I am now going uphill. No longer needing to fidget between 1st gear and second gear while turning, and having the jerkiness and slowdown when I shifted into 2nd gear.
Tonight's long ride on regular roads reaffirms to me that I was not dreaming nor making it up when I cruised in my neighborhood for 15 minutes earlier this day after doing the mod.
I finally tried this. I just used a loop of vacuum hose between the 2 capped vacuum outlets. Made use of a long skinny,medical clamp
that we use to get fish hooks out of the dumb fish that swallow the hooks. It fit through the tight spots to grab the rubber caps.
It doesn't make a big difference but it is a difference that you will notice.
I really notice it on lower speed, residential turns when trying to figure out if you need 1st or 2nd.
The throttle response isn't so on or off. It allows smoother riding at slow speeds.
I also notice there is less on/off, driveline lash at higher speeds. It does seem to feel like there is less engine braking.
I wonder if it allows a touch of "trailing throttle" so that the trottle doesn't cut quite as much gas flow when backing off.
Just guessing.
Oh yeah, and it will now idle along in first gear. It wouldn't do that before.
I kept meaning to update this. After a few months of this change, I realized that something was missing. My bike no longer had the edgy, instant throttle response that I liked. I changed it back to the stock setup and am much happier with it. Now if my allergies don't make me dizzy and spacey all summer like last year, maybe I'll get to enjoy it this year!
I posted some time ago #243, what I found was engine braking spewed fuel out like when first starting bike. My fuel mileage dropped drastically, so I changed it back. What made a more significant difference was adjusting my TPS as was suggested by Invader in a previous thread. Like a different bike, I have driven at 2500 to 3000 RPM in 3RD gear, and it is very smooth.
I have had this thread bookmarked since first getting my Versys, and will be attempting the mod today, since I'll have the bike half-apart to change spark plugs and clean the air filter.
Can someone please confirm that the diagram below is the best option. I have seen talk of other methods, but they all seem to lead back to this setup. I looked on the french site as well, and this seemed to be the method used (as best I could tell, without translation).
It seems I need to couple the carb sync fittings together using hose and T connector, and also cut the original hose coming from the IAP (far left fitting if sitting on the bike), inserting a T connector, which the single end of the carb sync T connector inserts into. Sound right?
I too have used this set up for 15 000 km and it has definitively made the bike much smoother at low rpm and got rid of the "herky-jerky" throttle.
I've been running a modified Cherry Bomb muffler, blocked off the PAR valve and have had no "popping" on decel with this mod.
FWIW - I just finished a 445mi run where I averaged on the highway around 5.5K rpm (70 mph) and got 48mi\gal. I've got stock gearing and she's a very smooth runner. Still makes me smile all the time.
The problem is you do not want a unrestricted vacuum connection between throttle bodies. It would have been a lot simpler for Kawi to do this than implement the more complex sync connection between the two. The reason for this is when one cyl is drawing air it will lower the vacuum in the adjacent cyl with a vacuum pulse. This makes the mixture richer but reduces performance slightly. If Kawi did not care as much about performance they would have used a much cheaper single throttle body that would have equalized vacuum like this. The reason for the dual throttle bodies is so the drawing of one cyl does not effect the other, also the large air box helps with this too - the volume of the air box is several times the capacity of both cyl.
I would like to see someone dyno their bike before and after this mod.
Sorry twowheels, are you saying there is a problem with the way I just set it up (method in the linked post - which bypasses the left sync port)??? Or just filling me in on the how/what/why of what this mod does, or why it's better with it?
Either way, I appreciate the post. . I'm just trying to get a definitive answer to what the common consensus is for the best method.
Hi,
the guy that invented this mod at first time connected left and right body by a line.
That is mod 1 (I made on my V).
After he made an evolution that is the diagram that you posted.
Your diagram is definitively ok.
OK folks. While I really appreciate all the help this forum provides, this is one of those times that each post gets me more and more confused.
The very first post of this thread contains the mod, as explained by Invader. The diagram I posted above is an exact replica of that first post (photo #3). My plan was to do exactly as Invader and the diagram described.
But after reading 11 pages of posts in this thread, it seemed that there may have been a change of heart - a more simpler way of doing it. MoFlow confirmed this by linking HERE
So I just completed the mod as described in the photo (also by invader) in the link above, NOT like the diagram I posted. That "NEW" way of doing it doesn't tie the two bodies together, then link it into the IAP line with a second T connector. It simply puts a line between IAP port on the left body, and the sync port on the right body - and with a T connector - ties that to the stock IAP hose.
The way I understand it is:
Version #1: tie both bodies together with line and T connector. Splice T connector into IAP line (both ends of the IAP line remain where they are from factory. Tie both T connectors together with line.
Version #2: Tie IAP port (on left body) to right body with line and T connector. Tie stock IAP line into empty side of T connector. No cutting the IAP line (gray). Don't remove rubber cap from left body.
Sound right? I went with the Version #2, based on the latest post from MoFlow about it. Is there a reason I should go back to Version #1, which is the way Invader originally posted it???
I guess I have more posts to edit... Go with the best and most simple configuration #1, with a single 6" (15 cm) long 1/8 or 5/32" (3mm) ID vacuum hose on both TB vacuum ports. Leave the left outer IAP hose alone, and forget about using a T:
Thanks for weighing in here. For the benefit of anyone who may read this later - the photo above is yet a third option, at least since my posts. Do you think there is performance benefit to going with this last option (in your photo above)?
I have already reinstalled the tank etc, and currently have it as the #2 option in my previous post (which I believe was originally posted by you somewhere).
If there is an improvement - I'll take it apart again. But if it would only be a simpler option, then it's probably MORE simple for me to leave the tank/air box on at this point
Appreciate all the help folks. Maybe there should be a definitive sticky for this mod???
Just a comment: You don't have to remove the gas tank to do the mod as Invader has just shown with the last set of photos. I was able to hook up the single line between throttle bodies with a nice long pair of needle nose pliars. Lot faster than removing the tank.....
I do remember reading that Scotty. I have a couple pairs of long needle nose that would be perfect for the job.
I guess I'm just waiting to see if someone comes back and tells me to go back to stock
I guess worst case - I could give it a shot as is, because at one point, the method I used was considered the best one. I'd like to hear if invader felt that tying the two bodies together with stock IAP hose performs better. Seems like he had tried them all.
Configuration #1 with the simple 6" long, 5/32" vacuum hose is the one and only which will give you the best results... I had edited my 1st post in this thread in Sept 2009, with detailed explanation. I could now add my good photo.
Configuration 1 works well. Also, no need to remove the tank.
Start by putting in the right TB nipple and connect it to the left one with a long nose pliers. U could use your fingers too if the engine is cold (easier and less prone to burns). :goodluck:
Fine, the goal for everyone must be to try and try to find his proper best riding setup :thumb:
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