Carb Vacuum Ports

[AlbertaClipper]

I have an '07 MRSV. Removed the AIS years ago. Was wondering if I can plug all 4 vacuum ports on the carb air intake tubes. These are the ports that you hook-up the carb sync tubes to when balancing the carbs. I have read you can possibly hook the two vacuum ports together on each side of the bike to get better low end performance. Has anyone done this? If so what were the results?

Thks

[videoarizona]

((I have read you can possibly hook the two vacuum ports together on each side of the bike to get better low end performance. Has anyone done this? If so what were the results?))

 

The Previous Owner did that on my 2005. I've seen no problems with that. Just one tube between the two on each side.

 

No performance issues, idle issue or mpg issues. Seems to be fine so I'm leaving it. Supposedly, it was done by him to reduce backfiring on decel. Not sure that helped as I still have some...but with HD mufflers on, I kind of like the rumble and noise!

[VerntureVet]

Jason's MOD

 

I tried it on my bike after syncing my carbs and could not tell any difference other than a change in my exhaust sounded a bit chopped like I installed a mild cam. Mind you I am running an almost straight exhaust so I hear every change @ full volume. It rained all night last night and this morning was unseasonably cold had to put on a jacket to not freeze my hangers off. I went to get on the gas in 4th and bogged out under load lost RPM @ 5k had to go easy to get home. Checked the sync on the carbs with minor adjustments and put them vacuum tubes back to stock. Let her warm back up and the issue went away.

 

Now for my run on about this.

 

If you think about it

We sync our carbs to get equal vacuum on the 2 cylinders. If you ever used a home made sync tube setup you would notice that when the carbs a in good sync that the fluid in the hose pulsates back and forth because the intake strokes on those 2 heads are back to back. Connecting the 2 ports gives the opposite carb a head start on vacuum but going threw that little hose there is not enough volume to really make a huge difference. V-Max engines do the same thing in a way with the V-Boost but it is done prior to the carbs and with a larger volume that can make a difference and then if I understand only when you are on the main jets under heavier throttle.

 

I can see how maybe it would help if your carbs are slightly out of sync.

 

Just my hypothesis.

 

I would have to see a dyno sheet on the same bike to believe it help more than it hurts.

 

An engine is designed to run a certain way. Although they may set them a little lean and detune them a bit for retail sale changing the design results in a balancing act. De-baffle your exhaust or run drag pipe (same concept) You gain some throttle response and high end power but suffer a drop in mid range operation. Counter act that by installing a simple toggle bold to break up the exhaust wave you get a little back but nor you lean. Jet up and you loose something else until you get it the way you want it.

 

When the day is over just remember live with the loss to get the gain you desire. I never found my Drag - Touring - Cruiser so I bought 3 bikes........

[Great adVENTURE]

I was curious about this so I took a look. My AIS is still hooked up and functioning but it appears the vacuum ports are connected together with a t fitting also. Any issues with this?

 

[videoarizona]

If she runs well and gets good mpgs... Guess that would be good!

[vzuden]

Looks like the Jason mod. Described in the tech section

http://www.venturerider.org/forum/showthread.php?501-The-Jason-Mod

 

cant say one way or another if it works as I have never tried it

Edited April 29, 2016 by vzuden
Sorry see Mod was already described

[MikeWa]

If the AIS is removed it is ok to plug the vacuum ports. I can think of no reason connecting two of them together should be an improvement.

 

Mike