My stock 82 carbs have gotta go. Obviously, a lot of folks have looked for a quality replacement for the setup on the Vision, and some have even claimed to have found one. But there is very little real information through the threads on what can be done or how it can be done.
Is this because the claims from others about a carb changover are a pack of BS, or is it simply that most of the members of our forum are more interested in tackling the challenge of getting the stock carbs to function correctly?
It seems to me that banishing these carburetors to the farthest ends of the earth presents basically only two major obstacles...
1. You have to attach different carbs to the cylinders in a way that will prevent vacuum leaks, cracking or stressing of manifolds, etc. Probably a custom manifold will need to be fabricated that has rubber expansions allowing for heat flex.
2. The new carbs need to be simpler than our Mikunis, yet deliver fuel/air mix evenly and smoothly without losing any of the powerband. Without an accelerator pump, the fuel supply at high end and low end will be at odds with each other.
I'm convinced that the idea behind the design of our carbs is a good one...adjustable for a variety of ambient temperatures, elevations, peformance types. But I think this is their downfall- they are too sensitive, too adjustable for the purpose they need to serve on the Vision. This bike has power that cannot be accessed because of carbs that cannot be tamed.
Put something simple on there that gives smooth fuel/air delivery across all rpm ranges, and declare victory. Right? What could make this a great enough challenge that very few of us have actually done and detailed here?
I agree with your thinking.
Quote from: Fuzzlewump on January 10, 2014, 01:26:10 AM
Put something simple on there that gives smooth fuel/air delivery across all rpm ranges, and declare victory. Right? What could make this a great enough challenge that very few of us have actually done and detailed here?
As much as I love this motorcycle, I wont put $1500 or any large amount for a single carburetor. I would spend a sizable sum to get fuel injection. Maybe we could get the single carb guy to sell us his bike and we could just copy everything for a reasonable cost.
If I knew a good motorcycle engineer I would ask him what he would charge to design a fuel injection kit and how much the kit would cost. I wonder would it be possible for a few Visionaries to fund a project like this from some reputable firm and then recover our expenses on fuel injection kits? ( Dreaming again Bobby) One other thought, do we have anyone with the courage to attempt to solve this problem if he were able to receive financial help from the rest of us? BDC
Fuzzle, I can hear your frustration and wish I had a simple answer for you. I think Bobby hit upon the main obstacle - cost. I'd say that many are drawn to the Vision because of it's low initial cost and/or they didn't fully appreciate what a "problem child" bike they were getting involved with. :D It's cost prohibitive to most Vision owners to undertake such a project or pay someone to take on the challenge. In many cases the mod would match or exceed the initial investment.
Even if you have the $ and inclination to do it yourself there is the time element. Even someone knowledgeable in fabrication and carb tuning is going to have a good deal of trial and error time invested. Most find it simpler in the long run to get the stock carbs working as best as possible. Those that have tackled the problem may have considered it a labor of love, enjoyed technical challenges, or may be ever so gently touched in the head. ;D ;D
I agree I'd be more apt to spend money on a FI system but even then can't see that kit being priced where I could justify spending the money. I'd find an "easier" bike to own before going that route. :( Maybe even one that's FI already!
What do other V2 engines use and why can't these be used on ours? There is obviously a reason but without thinking about it for hours..
Just about everyone was successfully using CV carbs at the time There were other carb choices Yamaha could have used. I think they were trying to innovate, think outside the box, re-invent the wheel, etc. ::) ??? :)
Honda, Suzuki, and Yamaha all had relatively narrow angle V engines with various CV carbs. Many could be adapted but each would be a project with mounting, cables, air filters and major tuning woes, yuck.
A friend who's into stand-up, 2 stroke jet ski's wants me to try the diaphragm carbs they were equipped with. He claims they're simple and easy to tune. Come to think of it HD's were factory equipped with Tillotsons for a while - maybe there's something to that! ;)
Thanks for that Rikugun. Never heard of Tillotson so I had to google and found this:
http://www.dansmc.com/pumper_carb.htm
It shed some light on those for me.
I picked up a clean set of throttle bodies complete with injectors and wires for a Suzuki SV 650 from eBay for about $60. You can find them from time to time at such a price, easier to find the throttle bodies at a good price than the CV carbs from the first generation SV. I think it would be easier to make the CV carbs work on the XZ than the fuel injection, but eother can be made to work.
With the CV carbs the main difficulty would be the actual fitting and linkages, as the SV carbs sit farther apart than the XZ carbs. With the injection system you need an electronic brain (ECU), cam position sensor, air speed sensor, engine temp sensor, etc., etc. plus a fuel pump to supply at least 42psi fuel. That also means high quality pressurized fuel lines. It can be done, but the CV carbs would be easier, I think.
Maybe a carb set up from a Honda Trans Alp or Shadow. Just a thought.
Personally, I'd prefer to go with a different carb over fuel injection. As Fret mentioned, there are a lot sensors and electronic bits associated with FI, and besides this I just like the idea of hard mechanical parts working in a "simple" way. This might come at the cost of flexibility, but that's a sacrifice I'm willing to make if the payoff is a bike that will at least hold steady idle.
I read that for many years Harley Davidson had problems with the attachment of CV carbs to the heads of V-twins. Apparently the temperature variations of an air-cooled twin caused the opposed cylinders to flex the metal manifold joints extensively, creating vacuum leaks. We already have rubber manifold boots, so with manifolds that are shaped the right way it should be possible to prevent this. With our liquid cooled bikes, would heat flexing of the joints be as bad a problem as it was for Harley?
My other main question is about the fuel/air supply of a CV setup. I like the idea of a single carb because it eliminates the synchronization and linkage factors, and it's one less carb to tune. But without an accelerator pump, it seems venturi and carb throat size will limit the power to either low end or high end only. Is it feasible to use a venturi that is set for low end power and put on an air scoop with butterfly valves to deliver more mixture for the high end? Will fuel metering be very difficult in the high end if you do this? Is this setup possible without vacuum actuation of slide in the carb?
I think something can be worked out, with the right determination.
Also, say you go with a dual CV setup instead of single. There is the linkage problem Fret mentioned, but how about balancing air flow then? Would synchronization be an ongoing issue with CV carbs that don't have accel pumps like ours?
(I say this because the accelerator pump's function is supposed to be seperate from the operation of synchronization, but it seems that adjusting the accel pump to remove off-idle stumble often changes my at-idle synch somehow. Also, there has been a lot of debate before about whether synch should be set at higher rpms than idle.)
I have always thought that the big 2 stroke carbs might be the easiest way to go as far as mounting and such. They are so short there would be alot of room left over. The one's on my stihl stuff just have a low speed and high speed adjustment. They could be just what the doctor ordered, but I have no idea. I don't know why they are so prevalent on 2 strokes and non existent on 4 strokes. I tend to think they may be less sophisticated and not as accurate on fuel delivery as they only have those 2 circuits. The jet ski ones may be different though. It's just going to take some work by someone to try them and see.
Jeff
I have a couple of roundslide 36mm Mikuni's waiting to be put on my bike. I'm just waiting until I have a free weekend or two so i can fab an intake manifold for them. Just going to use a plate of steel, copy the boot gasket then weld on an elbow/ clamp to these.
(http://stoddard.smugmug.com/Other/Vision-Pictures/i-zkrPXwn/0/M/20140111_222453-M.jpg)
That sounds like a great project Blake. You can't beat a good set of slide throttles for simplicity and reliability. :) I'll bet smaller sized than you have would still deliver better performance than the Vision carbs. Have you considered a phenolic heat insulator between head and manifold as part of the installation? Are they hi-perf or from a stock application? I like that they use cable operated "choke".
Fuzzle, there should be no problems like you described with HDs. While a single large carb might be easier to install, IMO 2 smaller carbs would offer better responsiveness and performance than a single carb - particularly at smaller throttle openings. Also, if you go with one carb it will prevent you from ever twingling (close fire) your V :o as the overlapping intakes will compete for a single fuel source. ;)
It's likely you will end up using individual "pod" filters and when fitted to CV carbs there are tuning challenges beyond those of slide throttle types. Regardless of the type used it's unlikely to be bolted on and have good fueling from idle to redline without lots of trial and error jetting. Even then, there is no guarantee you'll get it to the point of being acceptable.
"if you go with one carb it will prevent you from ever twingling (close fire) your V :o as the overlapping intakes will compete for a single fuel source"
If that were so then you couldn't use a single carb on a V8 or any other multi cylinder motor. :police:
When valves are open at the same time, overlapping or not, the motor just sucks more air through the carb.
Yup, all true and my statement was admittedly a bit cheeky as a humorous nod to the current close-fire topic. ;) However, a single carb sitting atop a V8 is not the only configuration available and not a decision made by efficiency or performance alone. Concessions are made based on the intended use of the vehicle as well as economy of operation and manufacture, performance, maintenance, etc. Regardless of application, the factory carb(s) quantity and CFM rating is sized appropriately by minds greater than mine. :)
There are a few (non-HD) twin cylinder motorcycles that use factory single carb setups. Sometimes they are lower powered versions of a twin carb counterpart. There may be a crank configuration (180 vs. 360) that may be more conducive for this relative to intake stroke spacing but I'd have to do more research to have an informed opinion. The same applies for 270 cranks of which I can't recall single carb examples off the top of my head.
Is a single carb Vision setup possible? Absolutely, it's been done a few times. Is it the best solution? I don't know. While this is a fun discussion, few have actually taken on the project of alternate carb(s) for good reason. Some may have gotten lucky on the first try. Others make claims and are not heard from again. Those that do succeed are sometimes closed mouth with the yummy specific details. YMMV
Quote from: Rikugun on January 12, 2014, 10:47:33 AM
That sounds like a great project Blake. You can't beat a good set of slide throttles for simplicity and reliability. :) I'll bet smaller sized than you have would still deliver better performance than the Vision carbs. Have you considered a phenolic heat insulator between head and manifold as part of the installation? Are they hi-perf or from a stock application? I like that they use cable operated "choke".
Carbs were off a snowmobile. I'd have to look up which one, but (A) they were cheap (60 for the pair shipped), and (b)- i liked the combined choke cable. with only 3 "jets" to mess with, tuning is a lot easier. I'll have to see how far off the jetting is as it stands, but hopefully it'll start up. The heat insulator is a good idea- might have to do that. I want to keep the carbs as close as possible to the head so i dont "have" to mess with tapering the intakes, and should just be able to get away with a single elbow.
the other thing i'll have to do with these carbs is figure out either a small electric fuel pump at about 1psi, or i was even thinking of getting the smallest car fuel pressure regulator i could find and free-flow the gas tank to that, and run it to the carbs at 1psi without a pump at all. Not sure how well that would work though.
Some have used motorcycle electric pumps with success and there are lots to choose from. I would think any from a carbureted application would be compatible relative to pressure.
Since the carbs came from a 2 stroke I have to ask about the emulsion tube/needle jet. Where it protrudes into the venturi is the top of the brass tube notched? Typically this was done on 2 strokes but not 4 strokes.
Naturally there is an exception that being certain HD carbs I recall may have had this feature on certain (older) models.
The stock fuel pump should work fine with these carbs. You would just need to work out the mounting of it. That would save you the expense and trouble of wiring an electric one.
Jeff
Would it be possible to make a single carb manifold sticking the carb out the side Harley style? Look at the pics of my rubbers turned over. That should place the carb low enough to sneak under the tank. Regarding size of a single carb it seems to me that it need not be larger than one of the stock dual ones since the engine only sucks air one cylinder at the time. What am i missing there? Anyway, a config like this wouldn't have to cost a lot.
This sounds like a great Kickstarter project with contributions from each of us to make it happen and contributing/sharing the results. www.kickstarter.com/
Previous members have spoken about cost and I agree, Unless a recarb could be achieved for less than $500 then it probably isn't worth it unless you have lots of money to spare. - That's not the reason most of us were drawn to buying a Vision in the first place.
There has been some work done here in New Zealand. Glyn converted his XZ550 to take an IDF Weber twin downdraft carb. (From an Alfa Romeo I think?) These come as 40, 44's and 48's, and have the advantage of having an accelerator pump. There are seems to be spares for these, they infinitely adjustable because they are used in performance cars, and they seem readily available on eBay. Redline are the US distributors of Weber. From this page, scroll down to the IDF series
http://www.redlineweber.com/html/Types/making_the_right_choice.htm
Glyn spent quite a bit of time having his manifold manufactured and modified to suit his setup. With The manifold boots reversed as per_w_aberg has shown, some careful work with CAD and then a 3D printed prototype, I reckon a lot of guess-work could be eliminated in getting the manifold right.
Here's what Glynn posted 3 or 4 years ago
Quote from: Glyn on May 18, 2010, 06:06:01 AM
Hi All, I've said all of this before, but I went down the road of trying to get my standard carbs to run correctly but just could not. I looked at the various options of alternate carbs, but figured that Yamaha had nutted all of that out so why re invent the wheel. Cruising through the local trademe site I saw a carb that looked almost identical to the Mikuni. A weber IDF carb. They have been out for ages and are a performance modification for various downdraft applications. They are put onto Harleys and Goldwings and those big boys suck plenty of fuel. The main advantage over the Mikuni is ease of jetting, better materials and just plain reliability. I've had my conversion of for a couple of years now. Never cleaned the carb and it just never gives me any hastles. Making the manifold is the most time consuming item. Mine was a one off which I machined up myself. Any decent engineering shop could improve on my efforts I'm sure.
You whack open the throttle and it just rockets away, no lag, no stutter, just like the Yam R&D man envisaged. He should have bought more pizza.
I haven't seen it in the flesh but some forum members on "The Mainland" acquired his setup when Glyn moved on from XZ's.
There are also cheap Weber-type IDF carbs out of China for about US$90 ea.
On another tack Treedragon (also in New Zealand) has fitted Webers from a Ducati Paso on to his XZ via a hand made manifold. You can see them on his pic here (from one of his previous posts). He seems delighted with the setup. No lagging coughing or gagging.
http://ridersofvision.net/rovforum/index.php?topic=14792.msg135644#msg135644
Close-ups of Glyn's weber manifold. I haven't bothered to take measurements as you can take these off the carb being fitted and the XZ550 intakes.
Where do you get Chinese IDF's for $90? That's less than the cost of a re-build kit which Glyn's IDF certainly needs
Thant's enough of that, I must concentrate on my valves
http://www.alibaba.com/product-gs/1479116749/BEST_WEBER_CARBURETOR_FOR_40IDF_WEBER.html?s=p
http://www.made-in-china.com/productdirectory.do?subaction=hunt&style=b&mode=and&word=weber+idf&comProvince=nolimit
Also, there is a Chinese/Canadian version by EMPI, HPMX 40 but these run at about $300. You might find a pair of Italian/Spanish weber carbs on a Porsche 914 here in NZ which would to the trick.
Interesting looking manifold. Looks like heavy plates are married to a central cast part.
manifolds made by butchering the Ducati Paso manifolds, re-welding, they fit into stock rubbers. A little hard to start when cold but runs really well. Throats have spacers for extra length. Uses XZ fuel pump.
(http://www.martin-rusholme.co.nz/weber_side.jpg)
(http://www.martin-rusholme.co.nz/Weber_top.jpg)
More suppliers of the Chinese Webers here, one company advertises that they supply single units.
http://www.alibaba.com/showroom/carburetor-for-40idf-weber-.html
Looking at both Treedragon's and POD's setup and the base of these Weber IDF's carbs, I would guess that it would be possible to have identical inlet pipes and flanges for both front and rear cylinders. This would make manufacture and installation a lot easier. Is there be any advantage in having a plate welded between the two inlet pipes?