Alternate Carb

[Glyn Pickering]

Looking at present and past posts at lease 30% seem to be carb related. It's an ongoing topic and you might conclude that the carb design is just... not good.

Has anyone given any serious thought too using an alternate carb from another v twin with similar power characteristics?
Either from a Yam or another make? I think it would make a great project - and since my bike is not a daily transport
bike I'd be keen to try something out.

Any ideas. Hey could someone also help me with the set up of e mail responses to posts ? see other topic.

Cheers

Glyn

[Lucky]

open up your original message, then look for "modify" on the top right.  your message will open up like your still entering it. at the bottom where you have the preview & post buttons, there should be  a check box to add an email notification with the post.
--Lucky

[h2olawyer]

Glyn -

As you've read, carbs and stators are the two biggest problem areas on the Vision.  The YICS is another frequent source of trouble.  The bike does run better with it hooked up & properly functioning.  It can be removed & caps installed on the fittings on the heads.  The Yamaha factory manual says the following about the YICS:

"To increase fuel economy through more efficient combustion, the engine is equipped with the patented Yamaha Induction Control System (YICS).  In this configuration, the YICS consists of a chamber linked to the intake manifold by a tube.  Upon intake, the vacuum in the manifold creates a vacuum in the chamber; when the intake valve closes, the chamber draws in some air-fuel mixture.  When the intake valve reopens, the mixture in the chamber shoots back out through the angled tube and into the cylinder, mixing with and swirling the main intake charge.  The swirling charge is then compressed and ignited, burning more completely and producing more power than that of a conventional engine."

A leaky YICS chamber causes an irregular idle - varying as much as a couple thousand RPMs.  Lucky's site (//www.xz550.com) has a method for testing and fixing the YICS.  It works - I did mine last summer and it's holding great.  The difference between a functioning YICS system and having it removed & capped is small but definitely noticeable.  As noted in another post on 7/31 (on this side of the international date line), the difference in idle speed is about 500 RPMs.  If you cannot get the YICS system functioning properly, it will run better with the system capped off.  One more fix is to replace the tubes between the heads & YICS chamber.  20 years plus all the heat they endure really softens them up and the vacuum can squeeze the tubes shut instead of drawing the air-fuel charge out.

The testing of other carbs has been discussed but nobody I know of has tried it yet.  I've seen one in the June Cycle World that has a Harley carb on it and I'm sure others have been done as well.  Fabricating the intake manifolds could prove the most difficult part.  If you have access to a dyno & exhaust analyzer, you can figure out the jetting easier than the trial & error of test rides.

A Vision with original carbs that are well cleaned & adjusted runs great.  I've even eliminated the stumble.  Cleanliness, proper adjustment of the mixture screws, synchronization and float level are all critical.  Make sure they are all set as well as possible and you will be rewarded with surprising performance.  Mine runs better today than it did when I bought it new in 1984.  All thanks to the information in this forum and Lucky's site.

I know this is a little long but I hope it helps some.  8)

H2O

[Blake]

Glyn,

Ive been one of the bigger people whos been wanting to try other carbs on the vision, especially the mikuni aftermarket carbs (roundslide / flatslide) simply because of their ease of tuning and flexibility, and hopefully their performance gains might help a little.  but like  H20 said, with the visions carbs nice and cleaned and synced' and with all vaccum hoses connected properly, the vision actually runs pretty damn good..its just the weird design of the visions carbs that makes it difficult to interchange.  And i DEFINATELY agree with H20... the most difficult part will indeed be fabbing up the intake manifolds.  the way im planning is just coming from the boots, and have the runners go straight out the side to the sidedraft carbs..definately a little challenge since the space above the manifold boots isnt much... between that height and the tank bottom.  and you definately dont want the carbs to be below the intake since thats just asking for problems.

but hey..theres always room for improvement eh?  hehe..



Blake

[wolfman]

I have often thought that the "Y" manifold and SINGLE side draft carb off a Harley Davidson (V twin) could be made to work realitively easily.  I am cheap, Harley parts are generally expensive, BUT, I have noticed the "manifolds" on EBay for less than $20...It then just becomes a question of getting them to seal up to the Visions intakes and of course tuning.  Given enough trips to the hardware store getting them to physically attach does not seem near the chore that getting it (the Harley carb) to actually work right would be.  (I'm no great fan of the V's downdraft Minuki's either)

[Blake]

If it helps any... what i was thinking was aluminum railing pipe (the thick stuff that they use to make railings that hold tourists from falling off cliffs for example)..  its near 1/4" thick (good for insulation from engine heat) and pretty much have "mandrel" bends (they're cast..not pipe..but has uniform diameter) that are quite sharp (almost immediate bend).. if you have access to a mig welder or know someone who could weld aluminum for you..that might be the cheapest and best best..i think a 90 degree elbow for that was around 2 bucks, and straight pipe a little more than a buck or 2 a foot. you could have a whole intake made up for maybe 20 bucks.




that or i dont see why a sheet metal intake couldnt be fabbed up, and maybe wrapped with exhaust wrap to insulate it..  might be cheaper...thats what ill probabaly end up doing at first..


I really would like to try and toy with the side draft carb idea before it gets too cold in SW Virginia....but the first thing is round slide or flat slide (leaning towards the roundslide at 100 bucks a pop as compared to the flatslide at about 150..) and more importantly..what size..im going to stick with either 34 or 36..but not sure yet..most likely will go with 34;s since the k&n's i just bought for the stock carbs will fit that (2.25" diamater)..

as for a harley carb.. yes it would work...and ive actually thought about that many times..i say if you want go for it..cant hurt to try..my only concern would be at the high end..would it hurt it or help it? only one way to find out...also lots of people have told me that the pulses from the intake flow hitting closed valves has an adverse effect on intake velocity...thats why i was opting for dual carbs...




Good luck, and if you actually start working on it keep me in mind..maybe we can trade "secrets" :)



Blake

[wolfman]

I can't imagine that the V's 550 cc's would pulse any worse than the far bigger Harley's V Twin does. ?Nice thing is that since the YICS canister works independant of the carbs and could be left on in place to continuing it's power and efficiency enhancing duties regardless of carb choice. ?I may just start to try and start putting together the pieces to make the attempt slowly (and cheaply) as possible. I'd be willing to wager that using a Harley "Y" manifold linking up to the V's intakes won't really be all that hard. As long as the flow rate (fuel/air mix in CFPM) is similiar for the single carb compared to the two Minukis I can't imagine any power loss being an issue.

[Glyn Pickering]

Wouldn't using a jap carb say off an XV750 or similar be alot cheaper to work with than Harley stuff? or would the space restrictions make it more sense to use a side positioned carb?
Perhaps there are some japas that use a similar setup.
Maybe a double carb setup from something like a XS650 could be used?

Just a note on the YICS hoses. Do they have to pulse or can stiffer vacumn hose or clear vinyl pipe be used with no ill effect?

Cheers

Glyn  

[Walt_M.]

I'm still looking for a deal on Keihin FCR downdrafts, 35 mm. My brother is looking for some and thinks they should be available. A set of 4 new ones is $900 and they should be cheaper used.

[Dan Byers]

Bernard LaJolie (sp?) has repeatedly stated that he had great success using FZ750 carbs on a Vision of his creation. I do remember several asking for, but not receiving details on how this was done. I know Bernard still reads and sometimes posts here, so maybe he can clarify what was done.

[Blake]

Wolfman,

definately sounds like your on the right track.. ?the imporant part WOULD be to make sure the cross sectional areas (or flow rates if you want) are at least the same, if not slightly smaller (better velocity). ?one thing i REALLY wish i could find would be flow rates for carbs (especially mikuni) having those would definately help with choice to figure what size carb would be best (especially for a single carb. ?just as a guess..maybe 40mm?) ?but yeah, youd be suprised how many parts on my bikes (vision included) are "harley" parts. ?my favorite place to "shop" is jireh cycles. they send you their catalog for free (around 100- or so pages..thicker than my phone books..about as thick as a big dictionary) and youd be suprised how cheap the "harley" stuff really is. ?(the turn signals i have are from there.5 bucks a pop, and now i have running lights both front and rear :) ) ?you might want to try there..when i get home ill take a look at the manifold, i swear some of them are no more than 10 bucks new.. that might work for ya.


Glyn,

Using a used carb definately would be cheaper (i actualy think maybe a cv carb would even help) ?but your right about the space restrictions for the side draft though. ?keeping the carbs inbeteen the engine and under the tank would pose a problem since youd have to take into concideration the pipe from the carb make a bend, then go straight down. ?thats why i was trying to see about making the carbs go out the side (one on each side). ?using a spare xs650 carb i had, you culd actually really tuck them close into the engine with one on each side if you culd get a sharp enough bend from the boot. ?the way i had them positioned the outside of the carb (bell is it?) they end JUST Slightly before the edge of the tank, so the airfilter would protude just slightly to each side. (would have to eliminate the yics of course, but i dont have mine mounted (or use it) anyway, so thats how could play.

Waltman,
If you ever do find a deal on the FCR's let me know.. i dont know about spending 200 or so per carb YET...untill we can figure out if another carb is viable to be easily adapted.  thats why i was concidering the roundslides as a "first attempt" (proflo for 80 bucks a pop for 34mm)...just something to experiment with to see if the theory would work.. but id definately be interested..  keep me in mind.



MAybe we should start a "alternate carb" committee :) haha.




Blake

[h2olawyer]

Glyn -

The YICS hoses should not "pulse".  If you are replacing them, you need to get tubing that is very stiff, heat & fuel resistant.  "pulsing" hoses diminish the effects thet Yamaha was trying to get with the YICS system.

I noticed that the tubes are still available from Yamaha for around $11.00 US but other suitable & less expensive options are available.

H2O

[Lucky]

1/4" fuel injection hose works very well for the YICS. it's very stiff & thinner to fit better on the YICS. I have it on mine & it doesn't pulse.  if your YICS hoses pulse, their worn out & ready to collapse.

--Lucky

[Rick G]

I tried  getting some info from cranky Bernie  (french wrench) but he looks down on all us mere  mortals and condecends not to answer emails asking for an audience. I believe he knows what he's talking about  and I'll be taking a trip to Tempe, to see if I can find his shop and determine if he's as rude in person as he is on the internet!

[Rick G]

On the subject of carbs , I get a little cranky myself . ALL old bikes  have carb problems . Try ressurecting a  four cylinder (pick the brand, it dosen't really matter which) There a lot more work and expense to rebuild and if they need diaphrams  , which run from 50 to 100 each , its easy to get 600 to 800 into a rebuild . Some can be  mickey moused to run reusing the old O rings and seats  , but your still  going to have 300 into a rebuild.
One of the reasons I chose the V was because of  easy to rebuild, simple carbs.
Some of you seem to think that your going to try starting an old bike that has sat around for who knows how long and just dump some fresh gas in it and it will start right up and you can jump on and take off . I've said this befor , but its worth repeating . Some one has gotten all the "good" out of the bike  if you want to use it, you will have to put the "good" back into it, The problems found on the Vision are common to ALL old bikes  to one degree or an other. some have far worse problems!

[Lucky]

Well said!
Cranky old bastard!  ;D

[Rick G]

Thank you!  Yes, I am!

[wolfman]

Actually getting the manifolds to mate up to the V's might not be as hard as I thought.  I just realized that if you remove the V's lower rubber carb to head manifolds and put them back on upside down, they will point 90 degrees IN instead of UP...

[Glyn Pickering]

Gee - looks like I've opened a bit of a hornets nest here. Point taken about diaphram carbs, they often go off. Carb would need to be nice and basic - like an old monobloc - maybe not..
Perhaps a s/h Harley carb off an earlier model? Did they change much during the years? The early 4 cylinder japas used non CV carbs, may be worth a look. Also in keeping with the more rugged looks of the vee.

That YICS is a sick joke. Tested two of the 3 I have off my spares bikes. Both leaked! The plastic looks naff and not up to the heat and vibration where it is positioned.
I'm going to make my own box (see seperate post) Got some new thick vacumn line today from local car shop. Should the pipes out. Really keen to continue the carb experiment thougth. At the risk of internet loonies, my mail is
pickteam@xtra.co.nz if anyone wants to swap ideas. I don't tap into this site often enoff to keep up with all the new stuff,
but often on my mail.

Ta for all advice. You guys are a mine of info.

Cheers

G 8)lyn

[Lucky]

Hey Glyn, don't be so hard on the poor YICS. For a bit of plastic that's been subjected to tremendous stresses, it held up admirably for 20 years.  If you simply open it up & reseal it, it works just fine...