Air Intake Question

[elmicko]

I looked around and haven't found a thread about this, so I apologize it it's been addressed earlier.

 

I've been working on my '86 VR since Thanksgiving weekend, just taking my time and doing maintaince / repairs and any mods I think need to be done. I started the bike last night so see if the new plugs I installed smoothed things out (they helped a lot) and noticed how much air the carbs suck with the tank cover off. It seems like the tank cover would make it hard for the bike to breath very good.

 

I know a few have opened up holes in the air filter box cover to get some more air in that way, but has anyone tried modifing the tank cover to help it get more air from the outside? Seems like it would help the bike quite a bit.

 

Thoughts?

 

Thanks,

Mick

[skydoc_17]

Hey Mick,

The combination of air flow into the engine and out of the engine is a concert of sorts. The restriction is not because of the air box, if you are running a stock air filter and stock exhaust mufflers then the bottle neck is in the air filter on the intake side and in the exhaust mufflers on the exhaust side. (if you don't believe me, take the air box cover off and try to rev your bike!) Not to mention the fact that the jets in the Carbs. control the amount of fuel that is delivered to the Carb. bodies. In stock form the ratio of fuel to air is set up for decent performance and decent fuel consumption. (a compromise) Drilling 50 holes in the air box is not going to allow any more air to pass thru the air filter. On my 87'VR I found that a change to a K&N filter, a rejet of the Carbs, and a set of free flowing exhausts improved the performance considerably. Quite a bit of time and money went into finding the right combination of fuel jet, air filter and exhaust. For the average rider, I think the money would be better spent on a new air filter, fresh plugs and wires, and a fuel filter change. Most riders don't need every bit of horse power these machines are capable of producing considering the speed limit is in the 65 to 70 MPH range on most Interstates. Even at 85 MPH which I saw while traveling across the North West these bikes are more than capable of running at these speeds all day long.

Just my thoughts,

Earl

Edited December 28, 2009 by skydoc_17
CRAYON BROKE!

[elmicko]

I guess my question is I don't have an issue with the air getting into the airbox. I'm just wondering if venting the tank cover would make it easier for the airbox to get the air it wants???

[dingy]

I drilled two 1/2" air holes in my air cover and it caused the bike to 'stumble' at mid range RPM's.

 

Duct taped holes shut and performance returned.

 

I have K&N filter in bike.

 

Exhaust pipes have rear tail removed and two 3/4" holes in last baffle.

 

This is on 83 - 1200

 

So my suggestion is to leave air intake system alone unless you want to get into rejetting carbs.

 

Gary

[Guest Ken8143]

I guess my question is I don't have an issue with the air getting into the airbox. I'm just wondering if venting the tank cover would make it easier for the airbox to get the air it wants???

 

I could easily be wrong but I don't see the tank cover restricting air flow to the air box.

[bobcat]

I live at 4500 ft and ride a lot at even higher elevations.. It seemed like my bike was running a bit rich due to the altitude so I drilled a couple of 1/2" holes in the airbox to get more oxygen..That corrected the richness and the bike runs great.

I wouldn't mess with your airbox unless you have a reason like I did..(altitude)

[elmicko]

I'm not seeing a problem with performance. What got me to thinking about it was when I changed the plugs. I don't know how long the old ones were in there, but they were pretty old. They came out black like the bike had been running too rich. I'm not planning on doing anything to the air box right now. The carbs need to be synchronized and I'm hoping to change the diaphrams pretty soon too, it just got me to thinking about the air flow thing. It seems to be sucking a lot of air to try to pull it all from under the tank cover.

[Condor]

I'm not seeing a problem with performance. What got me to thinking about it was when I changed the plugs. I don't know how long the old ones were in there, but they were pretty old. They came out black like the bike had been running too rich. I'm not planning on doing anything to the air box right now. The carbs need to be synchronized and I'm hoping to change the diaphrams pretty soon too, it just got me to thinking about the air flow thing. It seems to be sucking a lot of air to try to pull it all from under the tank cover.

 

I don't think there is an airflow restriction caused by the tank cover, but I guess the only way to know for sure would be to connect a vacuum gauge to the airbox somehow and see if there's a difference with the tank cover on or off. My '83 is runing fine with the K&N and MACs so I don't care.

[vic venture]

I too have been having problems with a float sticking but before I take the carbs off, I would be interested in opinions on the best intake K&N, pods...ie...and the best way to open up the exhaust system. I have read the many ideas but who can tell me for sure what sounds and looks good on these bikes. I would be interested on jetting ideas also. I do not want to be taking the carbs off more than once. it looks like a job. I have a 1984 Venture Royale 1200 that is stock with leaky carbs

 

Thanks:hurts:

Vic

[skydoc_17]

This first suggestion is for Elmicko, A lot of the First Gen. owners have done the "5Bikes" needle shim mod. What this is, is a replacement shim for the main jet needle. I manufacture a set of 4 nylon needle shims that can be installed that will allow you to "lean out" the Carbs. somewhat to get rid of the rich condition. They work great, they are easy to install without removing the Carbs. and will boost the gas mileage 7+ MPG. If any one is interested, PM me. I did a pretty nice write-up with pics on the Carb. Diaphragm Replacement, if you need that thread PM me.

This next comment is for Vic Venture, Unless you are dying to tear that Carb. set off of your MKI VR then I suggest that you open up the float bowls on the Carbs., and drain them. Then, using a can Of Carb. Cleaner, take the little red straw that comes with the cleaner and flood the Carb. Bowls with it. Let it drain, and do it again. If you use a whole can on the 4 Carbs. during an entire day, that's about good enough. If you need pics of the Carb. Bowl drain screws or have other questions about what I am trying to describe then PM me.

Both of the Mods I have described here have worked really well for me in the past and they are easily done with a minimum of tools, time and knowledge.

Earl

[Venturous Randy]

skydoc is dead on with his suggestions.

If you are seeing black spark plugs, it is obvious your fuel/air mix is rich. Along with what skydoc suggested, pull the diaphragm covers off and look at the diaphragms with a light behind them. Pin holes will reduce the vacuum that pulls the slide open and acts somewhat like a choke when the throttle plates are open.

The comments about re-shimming the needles is dead on. I was happy to get 40mpg on easy riding and now in those same circumstances I am seeing 47 to 48mpg. And my bike seems to be running stronger than ever. I also do not have any hesitations even though the carbs have been leaned some. And, I do not have as strong of a fuel smell when at idle. I found that going from the approximate .125 washer thickness to about .093 worked best for me. A little less than that, low speed performance suffered and I had stumble and hesitation.

I also have to admit that the air box on these bikes looks restrictive, but a lot of air can be moved thru that opening. More importantly, these bikes are extremely finicky on any change in this balance, as in trying to run the bike with the air box off. It just don't like all that extra air.

RandyA

[Yammer Dan]

K&N, Mufflers and HANG ON!!

[Dmnordin]

I have done the following mods to my '83 Venture; '86 1300 engine with 1200 carbs, Vboost (manually operated), carbs - re-jetted richer, 1/2 shim mod, new diaphragms,bowlgaskets,floats, stock exhaust innards cleaned out & replaced with straight thru glass pack inserts, individual intakes with 4 cone filters, later side covers with louvres permanently closed to keep heat off of me.

 

The bike runs great - oodles of power over the old stock 1200 engine, intake box w/K&N, and restrictive exhaust. & I haven't even cracked open the Vboost while riding yet.

 

I have about 2500 miles on the road since rebuilding the bike.

 

So, it's been getting kind of warm-hot lately into the 90's. and when I get home, I feel the plastic fake "tank" cover & it's pretty hot.

I think to myself after looking at things this weekend that the intake air is pretty hot from the engine heat, being trapped and all. My mind starts thinking that it might be a good thing to provide cooler air for the intake, and I'm thinking maybe venting the fake tank cover would do the trick. In dealing with my cars in the past, that was a theme it seams; cold air intake.

 

Any thoughts?

 

Doug

[dingy]

If you were to put a VMax air box on it, there is the possibility of creating a ram air setup.

 

The VMax air box has the intakes towards the front on both sides. It would be a fairly easy mod to duct air into these intakes through the two front air intakes on the front of the fairing that in the stock configuration push air down to the knee fairings.

 

I may play around with this next winter.

 

Gary

[Dmnordin]

Thanks for your input.

 

Yeah, I bought one on Ebay after I decided I didn't want to cut down the stock 1200 airbox to make it fit. After I bought the vmax airbox and started looking at how I would need to relocate the battery in order for the vmax airbox to fit, I quickly moved onto working on the individual intakes instead.

 

Yesterday I did think about re-routing some of the vent ducts, for about 5 minutes. I might re-visit it, but I don't want to give up the venting for ME lol.

 

It seems like the angled side parts of the fake tank cover would be a good place for some holes. It wouldn't be hard to dress it up/hide them with some stick on things from the auto parts store.

 

I'm thinking that just having it opened up some would be enough and that air would be drawn into the enclosed area - I hope it would - it would suck to end up venting the hot air out right in front of me! I have an extra fake tank cover - might be just the thing for a little experiment.

 

Doug

[islandmech]

This first suggestion is for Elmicko, A lot of the First Gen. owners have done the "5Bikes" needle shim mod. What this is, is a replacement shim for the main jet needle. I manufacture a set of 4 nylon needle shims that can be installed that will allow you to "lean out" the Carbs. somewhat to get rid of the rich condition. They work great, they are easy to install without removing the Carbs. and will boost the gas mileage 7+ MPG. If any one is interested, PM me. I did a pretty nice write-up with pics on the Carb. Diaphragm Replacement, if you need that thread PM me.

This next comment is for Vic Venture, Unless you are dying to tear that Carb. set off of your MKI VR then I suggest that you open up the float bowls on the Carbs., and drain them. Then, using a can Of Carb. Cleaner, take the little red straw that comes with the cleaner and flood the Carb. Bowls with it. Let it drain, and do it again. If you use a whole can on the 4 Carbs. during an entire day, that's about good enough. If you need pics of the Carb. Bowl drain screws or have other questions about what I am trying to describe then PM me.

Both of the Mods I have described here have worked really well for me in the past and they are easily done with a minimum of tools, time and knowledge.

Earl

 

 

I was wondering about the fuel milege with these bikes.... I have the k&n filter, the Mac pipes, I have dropped the needles {adjustable on my bike} adjusted valves, tuned up. etc. Bike runs great but best I can get is 40mpg {canadian gal} which is about 35mpg US ... I run easy because of low speed limits where I ride Any other suggestions??

 

Thanks, Gary

[Condor]

I was wondering about the fuel milege with these bikes.... I have the k&n filter, the Mac pipes, I have dropped the needles {adjustable on my bike} adjusted valves, tuned up. etc. Bike runs great but best I can get is 40mpg {canadian gal} which is about 35mpg US ... I run easy because of low speed limits where I ride Any other suggestions??

 

Thanks, Gary

 

The worse thing you can do to decrease gas milage is run it easy in 5th gear. Drop it down into 4th and see what happens. Use 5th if your slabbin' it, in a hurry, and don't give a hoot about gas milage.

[islandmech]

Ok I'll let R rev for a tank and see if it helps

 

Thanks

 

Gary

[Stache]

The worse thing you can do to decrease gas milage is run it easy in 5th gear. Drop it down into 4th and see what happens. Use 5th if your slabbin' it, in a hurry, and don't give a hoot about gas milage.

 

 

Kinda counter-intuitive, but absolutely true. I dropped a gear at all speeds for a couple of tanks bc somenone here suggested it. Went from 38 ish to 44 ish (Imperial Gallons) in town and fairly hilly. These things love to spin and the efficiency point is fairly high on the rpms.

[rjyammy]

I am wondering if you guys could help me with a few questions i have? I have an 84 Royale with airbox lid with holes drilled and carbs rejetted, i didn't do the work. I can only get about 35 MPG, would like to get more. I have a bag with factory needles, washers and some of factory size jets. Cannot find in factory service manual number of washers or thickness needs to be under the needle, anybody help? Have not taken carbs off to see what size everything is, would like to only do this once. Are the factory size jets and needle the best way to go? Have seen in previous forums about shim under needle? I have a stock airbox lid with no holes i can use. Any suggestions will be helpful.

[Condor]

I am wondering if you guys could help me with a few questions i have? I have an 84 Royale with airbox lid with holes drilled and carbs rejetted, i didn't do the work. I can only get about 35 MPG, would like to get more. I have a bag with factory needles, washers and some of factory size jets. Cannot find in factory service manual number of washers or thickness needs to be under the needle, anybody help? Have not taken carbs off to see what size everything is, would like to only do this once. Are the factory size jets and needle the best way to go? Have seen in previous forums about shim under needle? I have a stock airbox lid with no holes i can use. Any suggestions will be helpful.

 

 

Need more info than what you've given. Underwhat conditions are you getting the 35mpg. Never have had any luck with holes in the air box lid. Put the stock lid back on. Go back to the thread you found about the washers and do it. There's only one washer on the slider from the factory, and I don't think you'd be able to find them unless you find someone who still has a couple laying around after doing the washer mod. Check with Goose or Dingy on what you'd need to for jet sizes. Thinking about it gives me a head ache....

[dingy]

These are the four primary, replaceable jets.

For a set of 1200 carbs the jets are as follows.

 

Mains 117.5 - located behind fuel bowl cover in jet block, lower angled jet

PAJ1 #80 - Located at top of venturi

PAJ2 # 180 - Located behind diaphragm rubber

Pilot Jet #42.5 - located behind fuel bowl cover in jet block on right side

 

 

For a set of 1300 carbs the jets are as follows.

 

Mains 125 - located behind fuel bowl cover in jet block, lower angled jet

PAJ1 #80 - Located at top of venturi

PAJ2 # 170 - Located behind diaphragm rubber

Pilot Jet #37.5 - located behind fuel bowl cover in jet block on right side

 

Gary

[frankd]

Kinda counter-intuitive, but absolutely true. I dropped a gear at all speeds for a couple of tanks bc somenone here suggested it. Went from 38 ish to 44 ish (Imperial Gallons) in town and fairly hilly. These things love to spin and the efficiency point is fairly high on the rpms.

__________________

 

 

Sure is counter-intuitive to get better gas mileage at higher RPM. The engine is pumping more air and creating stronger vaccum in the intake manifold AND the engine wastes more energy fighting friction the faster it spins. However, several of you have said you get better gas mileage if you run it a gear low. Now, both of my First Gens pull perfectly everywhere from 1500 RPM up to 7500+ RPM, but in town I usually run it in the highest gear that will spin more than 1500 RPM. On my 89, the last tank I finished was some expressway, some highway, the rest was stop and go city. I got 44.8 MPG, and the current tank looks a little better. On the highway @ 72 MPH (actual--on the GPS), I got about 41-42 MPG. These are both a little better since I fixed the vacuum advance.

 

Because these bikes go down the road with so little throttle opening, the idle circuit in the carbs makes a lot of difference in gas mileage. If you've got the idle rich, your MPG will fall, especially at lower RPM. If I can find my official Heathkit air/fuel ratio gauge, I will pull the plugs in each exhaust pipe and see if I can measure the air/fuel ratio on all 4 cylinders.

 

 

Another interesting test......if the bike is actually getting better mileage down a gear, it should go faster in the lower gear with an identical throttle opening. If somebody has a throttle lock (AKA Vanda Cruise, etc.) and they were on a flat road in 4th gear, they could lock the throttle and see how fast the bike levels off at. Then without changing the throttle, **** to 5th and see what happens to the speed. If it goes down in 5th, the bike will get better gas mileage a gear lower.

 

Frank D

[rjyammy]

Here is more onfo. I have a K&N filter with stock pipes. My 35 MPG is running around 60-65 MPH taking it easy. The washers i have are .024" thick, are these stock ones? I have not tried dropping down to 4th, i will try next time.

[Condor]

Here is more onfo. I have a K&N filter with stock pipes. My 35 MPG is running around 60-65 MPH taking it easy. The washers i have are .024" thick, are these stock ones? I have not tried dropping down to 4th, i will try next time.

 

If you're running 3000 and below in 5th gear at that speed you probably will do better dropping down a gear. The sweet spot on these V4's is between 3-4000rpm. The faster you go in 5th gear the more wind resistence you're creating, and consequently will need to give it more gas to overcome it, but sometimes it just can't be helped when you're in a hurry. Around town down shift at 3000 and upshift at 4000. And controll the urge to drop the hammer....