Linking the Vacuum Ports

[Santa Hal]

Linking the Vacuum Ports

 

Taken from various posts on the VentureNet Forum http://www.venturers.org/NextGenTech/2ndGen/images/ais_tee.jpg This is a simple and near zero cost modification that improves low end throttle response and is claimed to increase gas mileage. (yet to be verified) The only drawback is that it causes a slightly irregular idle.

Step 1 - Remove the rubber plugs from the vacuum ports of cylinders 2 and 4 and the AIS hoses from cylinders 1 and 3.

Step 2 - If you have already disabled the AIS by plugging the hoses going to the exhaust ports, then the small rubber hoses attached to the vacuum ports of cylinders 1 and 3 can be left disconnected. For protection, they should be plugged. (a spent .22 shell fits very nicely)

Step 3 - If you plugged the hoses in step 2, then connect a piece of 3/16" fuel line between the vacuum ports of cylinders 1 and 2. Connect another piece of line between cylinders 3 and 4. Skip to step 5.

Step 4 - To leave the AIS vacuum control enabled, connect the control hose to a small T fitting with the other 2 ports of the fitting to the vacuum ports of cylinders 1 and 2. Repeat for the other side. (A suitably sized brass T is available from aquarium supply stores.)

Step 5 - Ride your bike and enjoy the increased performance and mileage!

[Freebird]

Sorry to disagree but I and many here have tried that mod and most are in agreement that it does nothing except create a bit of a rough idle. I tested it for close to a year and honestly found no improvement in performance or gas mileage.

[dingy]

Don't waste your time.

 

The inside of the vacuum tube is 5/32" in diameter. You are looking at a negligible amount of added air/fuel mixture flow. This was thought of as the poor man's VBoost, which is used on VMaxs to tie the front and back carbs together on either side above 6,000 rpm's.

 

I tried it several years ago and didn't leave it on long.

 

Also would you look at this thread to get your bikes info in your display.

 

http://www.venturerider.org/forum/showthread.php?t=58880

 

Gary

[Santa Hal]

Thanks for the info about the posting and I changed it. My problem is that I am getting poor gas mileage. I get about 36 miles per gallon. Went to Idaho with two up pulling a trailer and got 19 miles per gallon at the start of my trip. I ran seafoam all the way there and all the back, 4100 miles we went. My bike has K N filters, nasty boy pipes and now Iam getting 36 miles per gallon. I am trying to improve mileage. Before we left on the trip, Ponch adjusted my floats and we cleaned the carbarators. Thinking about rejetting the carbarators. I have 27000 miles on the bike. It runs like a bat out of hell. What to do?

 

Hal

[Freebird]

Mileage varies a lot based on how fast you are going, how heavy the bike is loaded, etc. 36 MPG is pretty typical on these bikes.

[mraf]

Everything you can. No one thing or mod will be the trick but a little here a little there eventaully will add up to acceptable M.P.G.. It's a never ending quest. Your handle about says it.

[eusa1]

i ran only premium fuel for several years and got about the same mpg that your getting, and when fuel prices went to 4 bucks a gallon i caved in and started running the cheap stuff.... i was amazed to get an additional 7 to 9 miles per gallon...

 

and as stated above.... all ya get is a blubbering idle with the prts hooked together.

 

enjoy the ride and try the cheap fuel... i also use seafoam on a regular basis.

mike

[Santa Hal]

have NOT disabled the AIS system,

 

:confused24::confused24:

[Carbon_One]

have NOT disabled the AIS system,

 

:confused24::confused24:

I don't think disabling the AIS will improve gas mieage.

On my bike I tried rejeting the carbs by going up one number for both mains and pilots. Gas milage suffered till I put the mains back to stock. I did leave the larger #17.5 pilots over the #15's in place and get a better low end off idle start. Plus I rarely need to choke the carbs either. Also before the rejet I'd get an occasional back fire in the mufflers on decellerating. Since going to the larger pilots that don't happen anymore.

I'm running with K&N air filters & a 6" shortened set of stock mufflers. The rest of the bike is stock including the AIS system.

Larry

[bongobobny]

The K&N filters are known to DECREASE gas mileage! go back to stock ones and see if it improves your mileage. Also if your carbs aren't properly sync'ed that too will affect gas mileage...

[Condor]

As already stated the Jason Mod doesn't do a thing for performance, but I'm going to do it anyway.. I like the lope. Otherwise the bike sounds like a machine gun.

On the mpg, new plugs and a Sync will help. Running Sea Foam has a tendency to foul plugs, and running it for the entire trip I'm surprised you got that good of mileage. Sea Foam will also cut into the mpg as it's less volatile and reduces the burn rate of the gas when used in large quantities. Last year I pulled a trailer to Cody and got 25-26mpg. Reg/no Sea Foam. Dropped the trailer and took a day ride to Shell Falls Wy. Got 40mpg on two tanks. So the trailer does take it's toll, especially on a motor that doesn't come on until over 3000rpm.

BTW I ran in 4th gear over the Sierra Nevadas, and 5th on the slab thru Nevada/Utah/Wyo, and it didn't make any difference in gas comsumption...

[muaymendez1]

I don't think disabling the AIS will improve gas mieage.

On my bike I tried rejeting the carbs by going up one number for both mains and pilots. Gas milage suffered till I put the mains back to stock. I did leave the larger #17.5 pilots over the #15's in place and get a better low end off idle start. Plus I rarely need to choke the carbs either. Also before the rejet I'd get an occasional back fire in the mufflers on decellerating. Since going to the larger pilots that don't happen anymore.

I'm running with K&N air filters & a 6" shortened set of stock mufflers. The rest of the bike is stock including the AIS system.

Larry

 

I have the larger for the Rstc sitting on my dresser.I lost the link to this done on the 96. I also fear gas milage would suffer.My bike is really cold blooded and pops on decel also but gets 41mpg almost religiously.

I would like to ride to work more often but 15 min warm up time changes my mind.

[GAWildKat]

The K&N filters are known to DECREASE gas mileage! go back to stock ones and see if it improves your mileage. Also if your carbs aren't properly sync'ed that too will affect gas mileage...

 

 

Is this only on the Ventures or on other bikes as well? Mike has a K&N filter on his Volusia, was the only brand we could get for his.

[stroker ace]

The K&N filters are known to DECREASE gas mileage! go back to stock ones and see if it improves your mileage. Also if your carbs aren't properly sync'ed that too will affect gas mileage...

 

 

Having a hard time with this, been running them 30+ years and I have never lost gas mileage. I'm not saying I gained either, I mainly run because of the clean and reuse benefit. My

[twigg]

Having a hard time with this, been running them 30+ years and I have never lost gas mileage. I'm not saying I gained either, I mainly run because of the clean and reuse benefit. My

 

It varies ...

 

K&N filters flow more air than most stock set-ups, and on some bikes require re-jetting.

 

On my XS750 that merely amounted to raising the needles half a notch to give a touch more gas in the mid-range ... that is where the fuel consumption can go up. You trade a few more hp for a little more gas.

 

As I understand it, K&N on the 1st Gens does not need any carb alterations, so the effect on consumption should be close to zero.

[stroker ace]

7 years and counting on this second gen. with the last 5 years with K&N's no change in fuel consumption no mods necessary. I personally have never had to change anything when using a K&N and have one on all my vehicles and motorcycles.

[Carbon_One]

Is this only on the Ventures or on other bikes as well? Mike has a K&N filter on his Volusia, was the only brand we could get for his.

 

Kat on the Volusia you will benifit with both performance & gas mileage by changing out both the pilot & main jets due to the larger air flow of the K&N filters. Later this weekend I'll send a detailed descricption of the jets you need from what I've done on those bikes in the past. Can Mike take off the carb and change the jets himself? Or do you think it may be beyound his abilities?

Larry

[bmxndad]

I can live with 36 mpg running 70-75 mph. Now if I get a little rowdy with the right fist and run 80 plus I will go down to 30 mpg in a hurry, and that is not be unexpected.

[muaymendez1]

 

Kat on the Volusia you will benifit with both performance & gas mileage by changing out both the pilot & main jets due to the larger air flow of the K&N filters. Later this weekend I'll send a detailed descricption of the jets you need from what I've done on those bikes in the past. Can Mike take off the carb and change the jets himself? Or do you think it may be beyound his abilities?

Larry

 

Whoa.Shame on you Carbon_one for even suggesting that somethinh may be beyond a guys abilities.Lol

How bout some info on the pilot jets you changed out.Ill keep seaeching

[joboo]

I have the larger for the Rstc sitting on my dresser.I lost the link to this done on the 96. I also fear gas milage would suffer.My bike is really cold blooded and pops on decel also but gets 41mpg almost religiously.

I would like to ride to work more often but 15 min warm up time changes my mind.

 

A little off the subject, but I wanted to comment on muaymendez's post, my 96 was exactly the same, and still pops on decel. I was really annoyed at the warmup time, have had the carbs apart a zillion times. The last time I paid particular attention to the choke which on the CV carbs is an independent circuit. The cables and rods can cause the choke to be completely off from one carb to the next. The choke has its own diaphragms and ports and they should all be matched to operate to exactly the same position on each detente pull of the choke. The cable that operates one side has keepers but if not lined up, bent a little or not tightened down in the right spot can cause two of the carbs to choke before or after the other two. The rods have the brackets with a set screw but these get a little bent over time as well. Once I got em so that they were all the same and really smooth, (the choke knob actually pulls really easily) I warm up the bike for a few minutes, the idle smooths right out, I ride at this point and I leave the choke out one or two clicks for another minute or two before closing it. No more 15 minute wait!

[muaymendez1]

I noticed my choke is either full on or off. Once I push in its shuts off completely.I will look into this thank you

[Santa Hal]

Kat on the Volusia you will benifit with both performance & gas mileage by changing out both the pilot & main jets due to the larger air flow of the K&N filters. Later this weekend I'll send a detailed descricption of the jets you need from what I've done on those bikes in the past. Can Mike take off the carb and change the jets himself Or do you think it may be beyound his abilities?

Larry

 

 

send a detailed descricption of the jets :cool10:

 

Hal

Edited February 19, 2012 by Santa Hal

[muaymendez1]

 

A little off the subject, but I wanted to comment on muaymendez's post, my 96 was exactly the same, and still pops on decel. I was really annoyed at the warmup time, have had the carbs apart a zillion times. The last time I paid particular attention to the choke which on the CV carbs is an independent circuit. The cables and rods can cause the choke to be completely off from one carb to the next. The choke has its own diaphragms and ports and they should all be matched to operate to exactly the same position on each detente pull of the choke. The cable that operates one side has keepers but if not lined up, bent a little or not tightened down in the right spot can cause two of the carbs to choke before or after the other two. The rods have the brackets with a set screw but these get a little bent over time as well. Once I got em so that they were all the same and really smooth, (the choke knob actually pulls really easily) I warm up the bike for a few minutes, the idle smooths right out, I ride at this point and I leave the choke out one or two clicks for another minute or two before closing it. No more 15 minute wait!

 

Ok so I found out that the left carbs were fully choked while the right side still had another click.Thr set screws linking both sides was off.In not sure if I got it perfect but they both hit the stops at thr same time.This should be an improvement.Riding to work in the am.Will report tommorow.

[joboo]

Don't think I have ever had to use full choke, I made the adjustments from off to make sure when the bike was on the pilot circuit it was only on it and when it needed choke it got just enough and evenly to still have a very smooth but slightly faster idle which is what allows you to ride it sooner instead of having a rough choke that is too fast to ride. Keeping the carbs synced after tampering with any adjustments is also real critical on these because of the smaller carbs and jets. Using the plastic tubes mounted on a board, I can sync these carbs in minutes once it has been warmed up. Using some of the tweeks the guys share on here you can keep your bike running better than when it came out of the showroom.