V-Boost on Venture Royale Question

[VerntureVet]

So I was @ the Grave Yard today and wandered over to the V-Max area to scope out some possible V-Boost parts. both the bikes that had it both missing the V-boost stuff. Can't imagine why...... But the one had just the parts under the carbs with no servo motor. It was just the tubes and the butterfly crossover things.

 

Now here is my idiot question. If I understand the V-Boost essentially opens up the intake between the 2 cylinders making the off carb. sort of act like a secondary. The controller monitors vacuum, rpm, and speed then tells the servo when and how far to open?

 

So what if one would use just the tubes and make them manually adjustable. With the valves set right to allow some but not full draw from the 2nd carb. Could that not correct a lean runner without a rejet or possibly give you the ability to tweak air fuel without messing with the carbs?

[cowpuc]

Sounds like a fun project Vern, definitely something this ol back yard mechanic would be interested in reading about (was a time not long ago that I would have been right in the middle of it with ya:big-grin-emoticon:).. In the end though, I really think an attempt at using a secondary to try to eliminate the need for jetting out of a lean condition is actually going to result in having the opposite effect.. Remember in the mid 80's when Honda came out with the twin carb single cylinder XR's? The system didnt last very long because of mysterious mid-range hesitation issues associated with that set-up. Sometimes the hesitation (bog at the wrong time is never pretty in the woods) was a blubber from to much fuel - Honda built in a reed valve to help with this, worked ok but even that was just not quite good enough.. Other times, mainly due to not having jetting spot on - a crack of the throttle was momentary lean creating more hesitation.. In the end, you will probably end up with wayyyyyyy more work in a redesign than 4 or 5 carb tear downs and rejets..

If your main concern is trying to overcome a lean condition and I were in your shoes, I would probably start with the basics - stock air box with stock lid so you have control of air flow. Check for airleaks on vacuum hoses, intake manifolds and even the sync plugs. CHeck the diaphrams for holes. If everything is airtight and still seems a little lean - before I would do a rejet I would shim the metering rods (these carbs dont have "E" clips like "normal" bike carbs,,, gotta be careful when I say that - someone just told me that the Canadian Ventures actually came with "E" clip adjustable metering rods ).. Anyway, pull the slides, pull the metering rods and fatten er up on the mid range - thats what I would do before I got into rejetting..

 

PS,, DONT FORGET TO KEEP US POSTED WITH PICS AND EVERYTHING IF YOU DECIDE TO CHASE THAT V-MAXING IDEA

[Great White]

Lots of guys have converted the vboost manifolds to manual operation. I forget the user name, but the chopped black Venture on the board here is one. Used a bicycle level iirc.

 

Not sure on correcting a lean condition if the jetting isn't right. The vacuum signal is the same so it draws the same amount from both carbs. It may work as you suspect, I can't say for sure.

 

I do know some guys leave it open at idle to wot and it supposedly gives a lopping idle like a big cam.

 

Even if it did cure a lean condition in one part of the rpm range, once you "got on it" it will likely lean out again at higher rpm....

[VerntureVet]

Sounds interesting was just my brain thinking the fuel from the 2nd carb would add to the A/F mixture ratio but Great White sparked a further thought. Same vacuum amount split over 2 carbs may just = the same amount of fuel until a high enough vacuum is created to demand more fuel than the stock single carb could provide. I suspect this is why V-Boost does not come on until higher RPM to avoid the midrange issues and open when there is enough vacuum to make a difference.

 

I would be interested in what the bike would do with it open all the time. I would not mind that lopping big cam idle sound. I wouldn't mind a more aggressive cam in general but I didn't find a lot of Venture Royale aftermarket parts. Maybe a V-Max cam is the best we can get. I guess if I had an intake to toy with worst case I just leave it closed until I track down the rest of the V-Boost parts on the cheap. As soon as I get back to work full time I will be getting a wide band A/F meter and we will just find out how this all works out. I may be reaching a bit far but I would love to see my project crest 150HP if not dream for 200HP without putting in a motor from another bike lol.

[Great White]

The limiting factor in the venture engine isnt just the cams. Its the heads. The vmax heads are redesigned to have larger port diameters and have larger valves to go with the longer duration cams.

 

like all engines, most hp gains live in the heads.

 

you'll be hard pressed to see 150 hp if youre expecting that at the rear wheels. The vmax boys have to get pretty involved to get there. Even fewer are running in the 200 hp range.

 

I'm putting the entire vmax top end on my bike this winter and will be pleased if i see 100-110 rwhp.

 

do some reading over at the vmax forums. Theres a coupke guys running manual controls for vboost and have it open most times. Generally, they seems to leave it closed until the 200-2500 rpm range.

 

i was thinking more about pulling from two carbs, pretty sure it wont make for a richer mixture as each carb is only going to pull stoich at best. More mixture, yes. But richer, nope.

 

Edited September 23, 2015 by Great White

[VerntureVet]

Maybe I will be sneaking in some new heads. I would love to bore it out this winter also but finding pistons is a PITA. But I assure you if they are out there I will find them. I am not a speed idiot and I am hardly ever on the twist past 1/2. But I like to know I have it if I want it + the ability when talking about the old hack job I can say. "Yea its kinda odd looking but it has balls LOL"

 

I also did some thinking about the V-Boost and if I am going to do it I will do it properly with a black box. Be it stock or custom. In the mean time I think I will fab up a cross over out of delrin that has an adjustable flow. should keep me busy a couple days and out of yalls hair with my silliness.

[Great White]

Big bore kits: http://www.pcwracing.net/page10.htm

Part of the VMax difference form the Venture is the pistons. VMax pistons have a pop up crown and the venture has flat tops. LIttle compression ratio bump on the VMax.

 

Used Vmax heads tend to go rather cheap on ebay. But try to find a set with the cams still in them so it's a matched set (IE: worn in together).

 

Most sellers pull the cams out of the heads and want lots of money for just the cams. When the pull the cams, they also tend to pull the shims and buckets to sell seperately also.

 

However, be aware that the VMAx stuff doesn't really start to "come alive" until around 5-6000 rpm. Bigger valves and ports can make it a little softer on the bottom end. I haven't heard too many guys complain about bottom end power on a VMAx, so it's probably not going to be a problem. I know my buddy's Max can boil the rear tire at will, so there must still be good bottom end power there!

 

Check out "Morely's muscle" if you want an electronic VBoost control. They sell Ignitech box with a VBoost control option. There might be another source for those, but I'm not a liberty to divulge what was told to me in confidence by Sean M. If you think about it, you might figure it out....

 

If your bike is a 1200, you might need 1300 carbs to fit hte VBoost manifolds. The VMax uses 1mm larger carbs then the Venture 1200s, but the same size carbs as the 1300s.

 

Big plus of using 1300 carbs instead of VMax carbs is you can retain the bar mounted choke. That may not matter to you if you are building a bobber. If fact, you may prefer the VMax carbs as the choke lever is on the carbs (IIRC).

Edited September 23, 2015 by Great White

[Yammer Dan]

Now I'm getting really cornfused!!! Im my humble opinion if you just hold it WOT it will run better......:banana:

[Great White]

Here's a little bit of interesting reading on a guy messing s not with vboost: http://www.vmaxguru.com/Tech/Gen1/VBoost/vboost_info.htm

[VerntureVet]

Interesting read. After reading that I did some digging on the Mikuni CV carbs and found his hypnosis about carb efficacy went boosting @ low RPM to be fairly accurate. At the lower vacuum the Mikuni carbs are designed to run off the pilot jets and the mixture is dependent on vacuum as much as it is by float levels. The amount of vacuum directly effect this circuits operation and fuel mixture. Connecting the 1/2 and 3/4 under lower vacuum actually will split the vacuum over both carbs making them not run under designed flow rates. The gained fuel from the 2nd carb is trumped by the less efficient carb operation. resulting in a loss of power in the low and low to mid range operation when the pilot circuit is doing most of the work. in the mid and mid to high range the slide opens with the needle allowing more air flow but the pilot is still a key part of the operation @ this point. Its not until the slides and needle are fully open the main jet kicks in and although the pilot is still delivering fuel its effect is less critical to the mixture. Also in the WOT high RPM >5500-6000 vacuum is no longer an issue with the slides fully open and the engine drawing harder the cross over vacuum is high enough and the split is less noticeable to the main jets than it is with the pilot that is dependent on vacuum to operate properly as designed.

 

This read and research has lead me to can the V boost ideas untill I can do it fully with a stock or self made black box.

 

This also made me head out and take off Jason's Mod because even though its a 1/4 in tube I am sure it has a direct effect on the pilot operation in a negative way.

 

On a side note during all this I noticed that with my choke fully off the 3/4 choke plungers were still pulled out 1/8in and the 1/2 were fully closed. after adjusting the linkage I re synced and the plugs are heading more brown than b4. Amazing how something so small being over looked made me want to change the bike. Under 3/4 twist now she is kicking ass. Just have to get into the carbs now and get those mains changed.

[Great White]

Actually, vacuum is a function of restriction. Vacuum signal is highest at idle and decreases with rpm/throttle.

 

Bernoulli's principle is what comes more into play at wot with increased flow rates and subsquent pressure drop in the throats.

 

[VerntureVet]

Actually, vacuum is a function of restriction. Vacuum signal is highest at idle and decreases with rpm/throttle.

 

Bernoulli's principle is what comes more into play at wot with increased flow rates and subsquent pressure drop in the throats.

 

 

So I have it backwards I'm working off google here lol. I know what you mean. Maybe the carbs when on pilot need the vacuum for the pilot to work properly.

What it all boiled down to was a lesson learned by me about MC engines and carbs. I have given into the fact I need to spend some $ on jets and a wide band air fuel sensor and rejet to rid my slight lean condition @ WOT.

 

The bike has plenty of power no matter what I do and what gear I'm in but when WOT in 4th or 5th you can tell the main jets kick in with a noticeable change in the sound of the engine. almost like I just dropped a 100lb weight off the ass end but no noticeable change in pickup.

 

Thanks for letting me prob your brains guys. This is my 1st tinker toy. In the past it was always a car. When you just bolt on some new parts and toss in a new tuner box. And that was on a 96 Mustang when you can just basically clone someone elses setup and get more HP with worrying about all the tinkering and jetting.

 

When this adventure is all over for me I will be obligated to keep the Yammy like I kept my 1st tinker car (1972 Valiant 318)

[videoarizona]

Thanks, Robert....think I'll go pull the mod off my scoot as well. Never could get a definitive answer about splitting the vacuum that satisfied me...

[Great White]

So I have it backwards I'm working off google here lol. I know what you mean. Maybe the carbs when on pilot need the vacuum for the pilot to work properly.

What it all boiled down to was a lesson learned by me about MC engines and carbs. I have given into the fact I need to spend some $ on jets and a wide band air fuel sensor and rejet to rid my slight lean condition @ WOT.

 

The bike has plenty of power no matter what I do and what gear I'm in but when WOT in 4th or 5th you can tell the main jets kick in with a noticeable change in the sound of the engine. almost like I just dropped a 100lb weight off the ass end but no noticeable change in pickup.

 

Thanks for letting me prob your brains guys. This is my 1st tinker toy. In the past it was always a car. When you just bolt on some new parts and toss in a new tuner box. And that was on a 96 Mustang when you can just basically clone someone elses setup and get more HP with worrying about all the tinkering and jetting.

 

When this adventure is all over for me I will be obligated to keep the Yammy like I kept my 1st tinker car (1972 Valiant 318)

 

Carb principles are the same whether on a car or bike. The execution is different.

 

It all really boils down to the Bernoulli principle. Pressure drop over an orifice draws fuel from below that orifice. The jet (pilot, main or otherwise) simply meters how much fuel is allowed to be drawn and mixed in the air stream.

 

The ideal is for the jet to meter just enough fuel to maintain stoichometry, which is the ideal ratio for the otto cycle engine (ie: 4 stroke engine)

Since a fixed jet can't deal with transient rpm conditions well, the tapered needles are employed to restrict the main jet at partial throttle openings and are fully withdrawn from the emulsion tubes at wot.

 

The theory is simple, the practice is fairly complex. When set up right, carbs are actually very efficient at what they do.

 

I also "tune" efi cars and diesels. I really don't like the word "tune", thats why its in quotes. I prefer recalibrate, but most people don't quite get the meaning these days.

 

I mostly mess with diesels now. They're actually simpler to do and a bit more fun because the gains for the work are much greater than a Gasser.

 

Carbs are what I cut my teeth on so long ago, kinda like going back to my roots.....And what makes messing with 80s era bikes fun for me.

 

[zagger]

I put V-boost valves on my 83 venture. I use a bicycle handlebar shift lever to run it so that it has 5 stops (clicks) as it is opened. I put the lever at the end of my left handlebar. It isn't clear to me if the absolute top end benefits very much since you have to be darned quick with the lever action as the RPM's peak. However, the engine runs noticeably better throughout the range with the V-boost opened a little bit (one click on my lever). Pretty unscientific and not a huge deal but I like it. The boost valves do need some space - in my case I don't have the usual venture plastic stuff so they fit without a problem.

zag

[VerntureVet]

@zagger any chance you have a buddy or something @ a shop with a dyno? I would be interested in how opening the boost under 5k changes the power curve.

Did you Rejet the carbs @ all?

 

Its back and forth with theory and application on if even a small amount of crossover @ low and mid range is hindering or helping.

[videoarizona]

Thanks, Robert....think I'll go pull the mod off my scoot as well. Never could get a definitive answer about splitting the vacuum that satisfied me...

 

 

UPDATE: Took off the 2 vacuum hoses and capped all 4 vacuum outlets on carbs. Went for a scoot test run. (that's how I justified it anyway).

 

Ran so much better. Seriously. I remember I posted somewhere a while back that I was mystified as to why the 1st gen motor ran so smoothly up to rpm's and the 2nd gen (mine) didn't. Well...the Jason mod was the issue. Now it climbs rpm's nicely, quickly and smoothly. Now it does feel like the same engine as what's in my 1st gen!

 

Done with that, thanks!

[zagger]

@zagger any chance you have a buddy or something @ a shop with a dyno? I would be interested in how opening the boost under 5k changes the power curve.

Did you Rejet the carbs @ all?

 

Its back and forth with theory and application on if even a small amount of crossover @ low and mid range is hindering or helping.

 

I did not dyno the engine and don't have access to the equipment. It's been a few years since I did the work, but I believe that I did change the jetting due to the many changes I made to the intake system on the engine. Each cylinder has a separate intake path with a pod type filter as well as a separate exhaust. I did adjustments based on a wide band air-fuel mixture sensor which I mounted into one of the exhaust pipes (a threaded connection welded into the exhaust pipe) and removed after the testing was completed. My observations on the manual V-boost are strictly seat of the pants. I wouldn't say that I've seen the V-boost valving add a huge power increase since my normal riding isn't at the top end of the RPM range. And cranking the V-boost open for a split second, right before shifting, isn't very practical and it would be very hard to judge the actual effect. On the other hand, for general riding speeds, etc. having the V-boost valves slightly opened does appear to increase the power down in the normal RPM range. This hasn't been confirmed by any measurements - just my opinion based on riding it. Gas mileage seems good - typically in the mid 40's.

 

The V-boost is interesting to mess around with but I wouldn't suggest that it will transform the overall Venture engine into some sort of superbike! I have no idea how difficult it might be to install if you are using the stock Venture intake system since the valves do raise the carbs.

 

In addition to the engine mods, I also stripped off the bags, fairing, covers, etc., etc. so my bike is undoubtedly somewhat lighter than a typical fully equipped Venture. That is another way to increase acceleration.

zag

[Great White]

"stock" venture with V-Boost:

 

http://i1174.photobucket.com/albums/r618/justonepict/10150718_10152337704828679_770325754_n_zpsckeelsqf.jpg

 

That was built by Morely's muscle, it's not my bike....but mine will be similar, minus the USD forks.

Edited September 24, 2015 by Great White

[zagger]

"stock" venture with V-Boost:

 

http://i1174.photobucket.com/albums/r618/justonepict/10150718_10152337704828679_770325754_n_zpsckeelsqf.jpg

 

That was built by Morely's muscle, it's not my bike....but mine will be similar, minus the USD forks.

 

Kinda resembles a Vmax engine.

zag

[Great White]

Kinda resembles a Vmax engine.

zag

 

It's a 1300 bottom end with a VMax top end.

 

Failry popular modification with the VMax crowd to easily get 100 cc's more.

[VerntureVet]

@zagger

My Venture is far from stock and I also have taken off most of the plastics. and soon the front upper cowling will be gone as well. I have tried to mess with the filter and intake with poor results. Do you recall what jetting you went with? Did you re jet the pilot and change needle or just the Main Jet?

 

I am still working off plug inspection until I get a Wide Band EGA and I am petty far out on the pilot and the needle is shimmed out with just one washer. It still looks and feels a little lean but not valve burning lean so I am considering upjetting the pilot so I have more room to play with it. I will be re jetting the mains this week as soon as I settle on a jet size and see if I can clean up my WOT leanness. With the exhaust dumped right after the combination chamber having no muffler and the desire to Mod the intake I am thinking about going with a 140 main then messing with the intake and then dial it in from there.

[zagger]

Sorry, I did all of the carb work about 7-8 years ago and the details have faded from my memory. I kept some written files with measurements and such but I went through them and don't see final details on the jetting. I'm sure that I thought I'd never forget - but I have. A wide band air/fuel sensor with digital display was very helpful to "see" what was actually happening inside the engine under different conditions. The one I used was like this: http://www.innovatemotorsports.com/products/db.php Innovate Motorsports has quite a few different systems and they have added new designs over the years. One nice thing is that the sensor and gauge can be wired into the bike so that you are able to observe the actual combustion situation under different riding conditions, speeds, acceleration, etc. I didn't use any of the data logging but you do end up with a pretty good mental picture of the engine combustion after using it for a few rides. It is necessary to solidly mount the sensor into the exhaust flow far enough from the exhaust outlet so that outside air doesn't mess up the readings. This requires welding a short threaded bung into one of the pipes where the sensor can be screwed in. The threaded bung can be plugged when the testing is done.

 

Of course, it is also necessary to sync the four carbs, but I assume this is a pretty standard procedure for most DIY folks. After a couple of misadventures using fluid filled tubing (slurped down by the engine), I rigged up a sensitive mechanical gauge with damping inside the tubing created by a couple of inches of threaded rod jammed inside the tubing. The restriction created by the small passageway along the threads steadied the gauge reading. Without some sort of restriction, the gauge simply flies all over the place.

 

"With the exhaust dumped right after the combination chamber having no muffler"

Isn't that just freak'n loud? My bike is far from quiet and it has four mufflers, one for each cylinder, with baffles and an adjustable flow restrictor inside each of them.

Hope this helps.

zag

Edited September 25, 2015 by zagger

[VerntureVet]

Yup a wide band sensor is on my list I found a few in the $150 range. as for the Jetting I think I will just be tossing in a set of jets and chopping a couple plugs to get it in the ball park for now.

 

Define loud. I never got around to MODing the chamber but looking into it from the outlets I can see right thru to the front pipes leading to it. But I do still see the mesh that is in there and im sure the baffle that separates the left and right is still in it. So I guess its kinda like a muffler....? My father in law lives next door and he has a 2002 flh dyna glide low rider. What I assume are after market pipes. I know for a fact he has baffles you can see them. His Bike is still loader then mine when idling. Maybe I am louder than him if I get into the throttle hard but its hard to tell. I don't make a habit of getting past maybe 1/3 twist because I still fear my mains are real lean with no mufflers.

 

What I did was remove the mufflers and installed a 1 3/4 to 2" adapter. Then on that I installed a 12" tail pipe with an angle cut and turn down.

Next time I am @ Menards I am going to pick some stuff up to put in an adjustable flow restriction of some sort.