Knocking sound from near Generator Housing area.

I was out last night and noticed a knocking sound once my bike was warmed up. Seams to happen when idling or under low load in 1/2 like when your trying to keep it @ 10mph in parking lots. Seams to go away once on the throttle until you hit the sweet spot cruising RPM around 2000-2200rpm. Some old timer @ the pit stop said it sounds like just normal engine clatter prob from the Gen mesh gear and lower end caused by the loppy idle and that V-Twins almost all have a knock sound once you CAM and Jam them and thats why Harley have a load exaust to cover up the engine knock lol. He said not to worry about it. I was afraid it was a rod knock but but it always goes away when you rev in N or once you take off over 2k rpm.

Normal?

If you are cruising around at 2K rpm you are lugging the engine. It don't like to run that slow. At parking lot speed I will be in the friction zone on the clutch to relieve some of the gear mesh sounds from the gear lash banging back and forth. These engines like to cruise around 4K rpm. You can drop to 3K around town in 1st or 2nd gear, but any less and you are lugging the engine and will hear it. This ain't a Hardly and it don't like to be treated like one.

I know its not a Harley I opted for the Venture because I live in a burb and every other nose upper has a new model Harley and thinks wearing a leather vest and cut off chaps, gloves make them a bad boy (no offence the that crowd) I just wanted to be different so I got an old Yammy.

Now I was not aware of the low RPM distaste the 1300 has. As this is my first metric bike and my first 4cyl. I assumed you want to be in the lower RPM (

I guess less 4/5th if me with the new pipes, rejeting and cleaning 1500-to 2000 is what I can cruise on @ 35MPH.

Now I can stop being paranoid that there is a bearing about to spin out on me.

Thanks again @Flyinfool

Check your carb. synchronization. If your carbs are way out of balance, the stronger cylinders will cause the engine to speed up, and then the weaker ones will cause it to slow down.......over and over again. This can cause the engine to sound pretty unhealthy.

I agree these bikes come to life above 4,000 RPM, but I normally let mine get down to 1500 RPM in any gear as long as I don't need to accelerate hard. Neither bike seems to complain when things are right. I'm not trying to start a fight or anything, but....I don't cruise in 3rd gear.

Ditto on the carb sync.

One other thing could be that your stator mounting screws could be a little loose. If the stator has been changed, it does happen that if the screws were not tight enough or not locktite in, they may work loose.

Randy

Welp got me four vacuum gauges from Harbor Freight for $20 with a %50 coupon my brother gave me. I connected them with = length fuel hose and each one I put on a vacuum restriction fitting and a copper manifold from pluming. I checked each gauge with a vacuum pump.

Changed Oil and replaced 1/2 quart with Lucas Oil

Changed plugs and wires

Set Idle

Synced 1-2 then 3-4 then 4-1.

Reset idle

Repeated several times until nothing changed.

She settled right down and the odd knock is almost gone.

I can't tell if it goes away over 3k if it does its not loader than my exhaust any more.

Thanks guys someday I will buy a real sync set but these ones I got did the job on a budget.

Throttle responce is back but still suffer from slower than expected pull (RPM gain) when WOT. It will get to 60-65 before redline in 2nd but it is defiantly slower to get from 4-7k in any gear @ WOT. I imagine its wanting more air than the stock air box can give it.

I had one of mine get so loose (had well over 200k on it) that it would rattle like your talking about while sitting on the kickstand, stand it up and it would quite down, pull the clutch in just a little and it would quite right down.. Did a make shift clutch swap on it (used clutch and springs) - found it helped a lot.. Almost sounded like forward gear noise..

Hey Vern, you get up this way on that puppy, stop in - I gotta good set of Gauges and between the two of us we can probably get those carbs pretty close to perfection..

Hey Vern, you get up this way on that puppy, stop in - I gotta good set of Gauges and between the two of us we can probably get those carbs pretty close to perfection..

250 miles 3.5-4 hour ride. Its getting colder so if we do this I have to roll the dice and hope my box bike makes it and some time sooner than latter. Just don't LOL @ my stripped down Venture Royale. I have a 2" tac on the handlebar and a digital reed speedo because the dash was gone and the speed trashed. I fixed it enough to get the cruise working. I 1/2 do not intend to keep any cowlings on it just the rear hard saddles.

My 1200 will cruise 2000 rpm around town with no complaints. Acceleration is a bit lazy there and just whacking open the plates will get some shudder.

I do tend to keep it more around 2500-3000 though. Throttle is just a little more controllable in that range for on/off transitions and acceleration is clean, regardless of throttle opening.

Pretty flat (comparatively) over 5-6000 rpm. Vmax heads and cams should fix that this winter....

Well last night I went threw the carbs again, installed better clamps on the lower boots, sealed the venturi boot better to the air box, synced the carbs again with my back yard vacuum setup, adjusted the pilot, installed 2X #6 washers on the needle instead of just 1, and put on new coils, wires and plugs.

Where did this engine come from is all I could say. It idles real nice now and even with the semi baffled exhaust it is not too load @ all. due to the rejet and exhaust mod I did have to open up the air Box some to let it have more air. That little knock is still hanging out but you can hardly here it now. I thought this engine had pull before OH boy now I have to hold on and dig into the seat to not get tossed off the back. Also consider I have removed close to 250 LBS of weight.

Just want to thank everyone here who offered advice and tips to get it to the point it is now.

Be careful messing with the airbox. I would advise you to start with small changes first.

It's not that it will go lean (although it can), it will mess up the resonance in the box and can cause the CV carbs all manner of fits. My SOHC 650 nighthawk was a beast on pods, when it decided to run that is. Most of the time it was just a big PITA. Temperamental is how I would describe it. I could get it to run great, but it would only last so long until something changed, it seemed like even the humidity changes would mess it up. Just too high strung.

EFI cares less about airbox dynamics, since atomization is a function of the nozzles and not the Bernoulli effect...

Be careful messing with the airbox. I would advise you to start with small changes first.

 

I know what you mean trust me. I tried making a new air box a few times and gave up and put the stock one back on. I did take into consideration the CV carbs this time and went on the safe side of just drilling four 3/4in holes on the lid @ the front and both sides. I then plugged all the holes with these 3/4in rubber washers pancaked with 1in washers. So far the best addition to performance without triggering the carbs to have a fit was 3 holes in the lid on the front side opposite the stock intake vents.

I know this is a MC and these carbs hate having the air box changed up, but some RAM air on any other carb always helps. I can't believe there is not a way to push more cool fresh air into these things without them tripping out.

If I were to hypothesize, I would say it's mainly related to the velocity of the airflow and the effects the air box has on that velocity.

The slides are controlled by pressure differential (related directly to velocity in the throats) above and below the diaphragm.

Increasing or decreasing that velocity friggs up the slide actuation. It has to be adjusted for by changing the slide port and/or spring strength.

Problem is: it's a very tricky balance. Engineers have done reams of calculations, modeling and testing to get it just right.

If the slide doesn't lift enough it's a problem. If it lifts too much, it's a problem. If it lifts too fast or too slow, it's a problem. All of this messes up everything from transient throttle response to jetting.

Changing the air box dynamics changes the velocity, which changes the pressure differential across the diaphragms, which changes the carb behavior.

That's my story and I'm sticking to it....

I like your hypothesis it is sound, or air tight in this case. So in theory I could take one of the carbs and connect the bottom to a vacuum and force the slides to operate under simulated conditions? As in if I was to record MAP @ the sync port, TP, and RPM along with what gear I am in and maybe MAF. I should be able to get the amount of vacuum under a given TP and simulate that on the bench. @ that point I would be able to bench test different intake setups and make adjustments to the spring to get it to behave.

If you think this is a feasible Idea I was already considering looking for some spare carbs to doe a full rebuild and rejet on so I can keep riding while messing with the carbs. I have most of what I would need to simulate it on the bench.

I don't know how you would read the differential across the diaphragm if that's what you're asking.

Maybe some pictures will help.

CV carb at rest, engine not running (the slide is actually up in this pic, but it will do for illustration purposes):

http://www.dudeworld.com.au/images/CV13.jpg

The slide is down at "OFF" and idle because the spring is holding it there. Pressure is equal on both sides of the diaphragm so it doesn't move.

Incoming air (engine running):

http://i1174.photobucket.com/albums/r618/justonepict/Air_zpszasimzlk.jpg

With the engine running (above idle and fast enough to raise slide) you get into the Bernoulli principle and it's effects on the slide hole in the venturi tube section of the throat:

http://i1174.photobucket.com/albums/r618/justonepict/Slidehole_zps9vpvvutb.jpg

what happens is a pressure drop below atmospheric pressure in the throat. The slide hole makes the area above the diaphragm a common chamber with the carb throat so it experiences the same pressure drop (it also adds more pressure drop due to the slide hole being at a right angle to the throat airflow):

http://i1174.photobucket.com/albums/r618/justonepict/PressureDrop_zpsvxmugek0.jpg

when the pressure drop is enough, atmospheric pressure (which is ported to below the diaphragm) overcomes the spring pressure and the slide starts to lift:

http://i1174.photobucket.com/albums/r618/justonepict/atmospheric2_zpsbzx5co1g.jpg

The more you open the throttle, the more Bernoulli effect in the venturi, the lower the pressure above the diaphragm, the higher the slide is raised by atmospheric pressure.

Really quite ingenious.

So if you were to try and measure the pressure drop, I guess you would have to tap it off one of the carb tops above the diaphragm. Maybe with a fitting through the cap/cover or something....

@Great White

What I meant was measure MAP @ the sync port and pressure prior to the venturi in the airbox and maybe flow into the air box. If I data log those 3 values along with T-Position and RPM I could in effect simulate air flow threw the carbs and cause them to operate as if it was on a running engine. In doing so they SHOULD act the same way as if they was on in engine. Including them wigging out with no air box when flow is increased and the throttle is opened.

In doing this I can make a clear airbox and use my slipstream smoke machine to get a look @ the flow inside the BOX and hopefully be able to redesign the air intake to give them the flow they want and need to operate.

Fluid Dynamics formulas should allow for a more efficient re-design that takes into account faster more dense air. I see now why the carbs have fits with the air box off. Particularly with the venturi off. As the port hole to the diaphragm is slightly obstructed by the Venturi boot.

Thanks for the visualization

That's just the "air" side of it.

The fuel side is another story.

For example: Changes in velocity also effect the emulsion tubes, which are critical to low speed and transient operation....and believe it or not, WOT also.

There's also resonances to be considered when designing an air box.

Get a resonance at the wrong spot and you may go lean or rich at differing RPMs and have no idea why.

"Air box" makes it sound so simple. How hard can it be to build a "box"?

But the science behind it is just crazy. What seems like "more air" often means more problems and/or less power. Or, a bump or curve in the wrong spot and it all goes to H-E-double hockey sticks......

AHHH so the lower pressure caused by the increased speed of the air threw the narrower part of the carb (blue line area) as air passes. Is over come by the Higher Pressure Being drawn in from the wider port opening near the the opening of the carb.

But with the venturi boots you are already lowing atmosphere pressure when the carbs draw more volume. So that makes a lot of sense why the carbs trip out with the Venturi boots removed because they are designed (threw the spring) to expect that balance. Taking off the boots throws off the balance and makes them trip out. I would also expect that is why the air box is designed as it is.

Now that I have a clear understanding of the CV carb design I am sure if I had a spare set of carbs I could get them on the bench and simulate driving conditions by using vacuum pumps and a PLC. I could then design boot adapters, filters, and air intake pipes that will draw air from just the right place for the diaphragm pilot (yellow line) and the slide hole pressure to be in a proper balance to allow for Ram Air / electric turbo to work and not wig out the carbs. It may require some adjustments to the spring but I should be able to pull it off without modding the carbs @ all less a minor rejet to compensate for the more free flowing exhaust. (that I have already done but I'm talking dyno tuned after roughing it in). @ worst case it may need a logic circuit connected to MAP sensor output and a shuttle valve to change the flow rate or location of the pilot air.

Let me track down some working used carbs and see what I can come up with. If I can't get it all to work out I will just 3D print a new intake an make the thing FI with a MegaSquirt. I didn't want to go the full FI route due to the cost of adding all the sensors and having to mess with all the tables to get it all locked down.

What seems like "more air" often means more problems and/or less power. Or, a bump or curve in the wrong spot and it all goes to H-E-double hockey sticks......

I am not just tinkering here and just because its just a Venture is no reason not to work it all out while I'm off work I need something to pass the time. Last spat of slow work I had 10 years ago I dug my teeth into a 72 Valiant 4 door that had a 318 V8. The stock 230 BHP on paper brand new turned out in 2005 to Dyno out on the tired 90K+ mile engine to be more like 130ish @ the tires. My target for that was 450 @ the wheels and I got Laughed out of the shops. 5 years of work and tinkering including but not limited to bore, deck, 340 head swap with P&P dual 4brl Edelbrock 750s, headers, 2.5 in flowmaster....... After the cams and pistons and all that I was making close to 350 @ the wheels. I dropped on a super charger and had it damn close to 450 when I finally called it good enough to prove I could do it with a 318 block lol.

The first LT1 Camaro that thought I just had a cool exhaust and some ego found out what my 4 door sleeper could do. I feel the Ventures 1300 can get 150 ez with some work. When its said and done I can add it to my collection of learning projects in the barn. Maybe next to the 70MPH Schwinn Meridian with the electric hub motors ;-P Most new visitors just look @ them and say What is that thing. I will be able to say "Oh thats a chopped up old Yamaha Venture Royale. Wanna take it for a spin?" LOL

Thanks again for the knowledge I hope to put it to good use.

Barely scratched the surface on cv carb function my friend. Im no expert on them either.

Something else to consder if youre building a bench rig is reversion.

Each carb is feeding only one cylinder, so you're essentially running four thumpers on a common crank.

A constant source airflow like a pump isn't going to simulate the reversions that a single cylinder makes. In a nutshell: the intake valve slamming shut creates a reversion wave in the intake tract.

Multi cylinder engines like a v8 or v6 (even an I4) feeding through a single carb have this effect greatly reduced due to the intake volume (mainly the plenum volume). They do deal with it, but the effect is so reduced that engineers pretty much only design for it in the runners themselves.

Bike engines don't have a plenum and a very short intake tract, so they have to deal with reversion pretty much right up to the air box. This is often where resonance is put to good use and it counters the reversion wave.

Crazy amount of science and experimentation behind the whole thing....

The thing about the Venture is that it's like every other engine out there: the power is hiding in the heads. Valves, porting, ports sizes, cams, etc. That's essentially what they did when making the Venture engine into the VMax and pulled ~145 bhp out of it. Haven't seen a reliable hp number without V boost, but guestimates on how much it adds run from 5 hp to 20. Someone will need to do a dyno run with it on and with it off to know. The stage 7 kit doesn't use vboost though. It's deactivated.....

Sensors for efi can be had dirt cheap. Just take a tip toe though any u-pull yard and you can be all set up for under 50 bucks. Gm vehicles are a good source for generic style sensors, manily because the general builds pretty chesp cars and they typically lack in sophistication (not those high end stuff, the day to day stuff).

I usually bring coffee for the hard monkeys when shopping for sensors and get away even cheaper than 50 bucks....

Can't help with building the lookup tables though. That's just plain old head down and get into 'er work.