Two barrel carb swap

[BlueSky]

I stumbled onto this video of a single carb swap for a Gen 1.

 

[Patch]

At 3.34 seconds into the video.... Tell me honestly that you would except the stall in flow while cranking it off a light?????????????

At Idle do we hear what we would expect to hear off a high lift cam pulling past idle positioned throttle plates? Ask why that is.

Progressive 2 barrel carburetor that dates back to the early 70s for the 2000cc early British Fords, it was slow to kick then on those beaters, of little use on a performance machine!

Reach out to this fellow, invite him to the forum where he can brag and perhaps he may learn a thing or maybe nothing as he has so much experience having done this once before on a wing???

And maybe Puc can teach him some welding lessons while he here??

Just a thought

[bongobobny]

Hrumph!

 

Sure seems to lack throttle response, doesn't it?!!?

 

Hey, I know very little about welding and even I can see it looks like crap!

 

Sure, it costs a lot to PROPERLY rebuild our carbs and PROPERLY set them up but when done it makes for an extremely great running engine. I am also concerned about the longevity of his valves without the proper backpressure due to his "modified" exhaust...

[Patch]

Hi Bongo!

I agree with the slow response to rpm. In those vids that I have seen posted the slow response is most striking, also noticing that those I've seen have flow stalls around climbing rpms. Again and as we said in the other post restricting air flow comes at a cost. With such a small plenum throttle plate angles work against flow and will cause flow to shear as it moves across the plate leading and trailing surfaces. This angle will also cause the flow though to deflect of the apposing plenum wall, this creates an eddy current that starves ports!

If the exposed welding is as we see here then what attention was paid to the inside? How can one be sure there are no vacuum leaks?

 

I have first hand experience with that carburetor, it was good in its day but was designed around compromise and for a very different intake manifold.

 

We didn't cover back pressure in the other thread and I personally have some very different thoughts around it. This for the most part started with the early 2 strokes which as you all know have a very different design and, back pressures were interfering with filling. On these 4 strokes most have collectors, the piping runs often end up different front and back. There is a difficult to understand sonic plus that takes place which is usually time for best scavenging on naturally aspirated engines. At the same time we try to time our pipes to assist one another through scavenging. The best way I know to explain this is thinking around flow moving past another chamber (equal or not in size) which creates a low pressure (Venturi rules) and this movement will cause scavenging (like adding concentrate to a moving flow)!

So usually it is safe too say after the collector you can choose to dump or, the job is done. The back pressure would be best serving if kept as low as possible but high enough to not brake or separate exhaust flows in chamber, think of it as a train loosing momentum and you develop a clearer gotcha;) So keeping exhaust in the pipe moving requires some consideration and minimum back pressure. This is most critical at higher rpms where filling drops off do to fresh fluid flow restrictions above and at intake strokes and is where we face the decision of velocity verses volume.

[cowpuc]

Personally I LOVE what the guy did and give em a double dip:thumbsup: ,,, of course,,, if you are the builder and reading this = ya gotta consider the source on that :thumbsup: cause I am farrrrr from anybodies mother on this stuff!

I have yet to meet a carburated motor that has any form of decent throttle response when cold,, just nature of the beast IMHO. My experience has been it is VERY difficult to judge performance until she's up to temp.

Yep,, the guy DEFINITELY would not pass an xray or pressure test on a power house job site with those welds but I have seen far worse.. Heyy,, he tried and that counts in my book.. Welding advice? Practice until you can SEE the puddle! Once you can develop that basic skill, those welds will become "wedding ring bands".

IMHO, sound/rumble is a deceptive thing.. I am with Bongo 100% on the whole put the :mo money:toward the OEM quad carb setup to bring it back to life. Set up like those early engineers at Yamaha did in their RnD to make these 1st Gens run like a scalded cat in the first place is THE way to go IMHO (and Bongo's )..

 

About the only place in the vid that has me my beat up ol beaner is the young mans comment about doing the single carb setup on a wing and then seeing 170 mph on it .. Anyone who has actually seen 170 mph on two wheels KNOWS that is probably stretching it BUT,, he does not go into what kind back ground he has in frame design and steering geometerys and the like so I spose,, giving him the benefit of the doubt, it is possible that he built up a wing motor and stuck it in a Bonneville streamliner frame.. Of course, if that were the case,,, one would think his weld skills would speak to it

 

[BlueSky]

Found an update video

 

[bongobobny]

Well, the idle sounds a little better now, shame he didn't blip the throttle a couple of times to see if the response improved any as I noticed the temperature gauge was indicating it was somewhat warmed up, indicating about halfway. On the '83 and '84, it was normal for the temp gauge to read 3/4 or above...

 

40 mpg is about the magic number for a 1st gen but he is stating a lot of stop-and-go so I would be interested in highway mileage as long as he keeps it around 70 or less as we all know our mileage goes to pot at speeds around 80 and above.

 

Steven G., Yes I can see where the "bell" effect will most likely be hampered with his design intake. The stock intake is pretty much a straight shot and I doubt that there are any eddy currents with it. As far as the exhaust, I agree the collector does it's thing pretty much but I still am concerned whether or not there is still enough back-pressure to ensure it not burning valves. I guess time will tell with that...

 

Sorry, but I will stick with our highly efficient 4 carb system that each carb can be "tuned" to the individual piston (balanced for equal flow to each cylinder I.E. "Sync'ing them). Maybe he will get a compatible gas mileage but I wonder if it will accelerate as well.

[CaseyJ955]

I really like this. I'm going to give him props for taking something on that MANY have discussed, including myself. I have totes of old VW manifolds and Weber carbs to give it a throw, just have no good place to do it until I relocate. I'm still unconvinced that a single barrel is ideal, one or a pair of non-progressive 2bbl Dellorto or Weber carbs I think would rock the house, but drive up the cost considerably from what the guy in the video has done.

 

I'm thinking that the 4 carb system is ideal when it works right, we cant argue it's pretty darn good. I know there are many folks that own 80s model Yamahas that may not have gobs of wealth, and just want to ride. Even if the carb conversion is a little bit south of the performance I can see a market for it for those that maybe dont want to take on the expense, rebuilding/dialing in the CVs. Getting the factory CVs dialed in can be a serious pain in the ass, we have seen more than a few people struggle with getting the bikes right while fighting the OEM carbs. That many more on the Vmax side too.

 

I can definitely see value in an easy to maintain, no synch necessary, slightly less awesome, much cheaper, easier, more reliable way to just get out on the bike and ride. I think this would be a hit if it does that and still gets acceptable MPG.

[bongobobny]

 

I can definitely see value in an easy to maintain, no synch necessary,

More like no sync possible!!! The main reason/advantage to syncing our carbs is so that all 4 cylinders operate as close to matching as possible which maximizes performance. When the 4 cylinders are not perfectly matched they "fight" each other (albeit to a small degree) and rob power...

[CaseyJ955]

More like no sync possible!!! The main reason/advantage to syncing our carbs is so that all 4 cylinders operate as close to matching as possible which maximizes performance. When the 4 cylinders are not perfectly matched they "fight" each other (albeit to a small degree) and rob power...

 

I can feel when it's time to synch and I dont mind doing it, it's quick and easy, but I know not everyone shares my enthusiasm for it. A common plenum intake design should alleviate to a large degree the need for individual throat synchronization. It's hard to beat the OEM rack from a performance standpoint, but I know not everyone has the time and patience to do said maintenance, and maybe not the $$ to pay a shop every time they get finicky, and they do.

 

I've read so many posts in which folks were at the end of their rope with carbs and fuel management problems, folks that I know just wanted to ride, a nice easy kit like this might have some benefit for those who dont want to hassle with the OEM carbs, they sure have a learning curve to tune, or a pretty large expense if someone pays a shop for the labor.

 

What I reaally want is to see some dyno runs including power and tq curves, and actual MPG data. It's impossible to judge if it's a worthy compromise when we still dont know what the real world compromises will be. While I'm in agreement that the OEM carb rack is about as good as it gets for these bikes, I think there is some value in sorting out an alternative for those that prefer to avoid the hassle and expense of the OEM rack. I'll bet that a properly chosen and tuned performance oriented non-progressive 2bbl would operate well enough that the average rider would be hard pressed to feel much compromise, maybe a little at the pump. Carbs like Weber and Dellorto offer a great deal of tune-ability, even different size drop-in barrels to change the MM spec. I have little doubt that one could be tuned to work correctly on these machines, but not necessarily at a great savings over the OEM rack rebuild. I'm thinking that intake design is at least as critical as carb choice. It would be slick to design a single plenum upper manifold to bolt right to the OEM intakes.

 

As I'm typing I have a mental image of my Vmax with a pair of 36 DRLAs on a custom intake haha.

[cowpuc]

I can feel when it's time to synch and I dont mind doing it, it's quick and easy, but I know not everyone shares my enthusiasm for it. A common plenum intake design should alleviate to a large degree the need for individual throat synchronization. It's hard to beat the OEM rack from a performance standpoint, but I know not everyone has the time and patience to do said maintenance, and maybe not the $$ to pay a shop every time they get finicky, and they do.

 

I've read so many posts in which folks were at the end of their rope with carbs and fuel management problems, folks that I know just wanted to ride, a nice easy kit like this might have some benefit for those who dont want to hassle with the OEM carbs, they sure have a learning curve to tune, or a pretty large expense if someone pays a shop for the labor.

 

What I reaally want is to see some dyno runs including power and tq curves, and actual MPG data. It's impossible to judge if it's a worthy compromise when we still dont know what the real world compromises will be. While I'm in agreement that the OEM carb rack is about as good as it gets for these bikes, I think there is some value in sorting out an alternative for those that prefer to avoid the hassle and expense of the OEM rack. I'll bet that a properly chosen and tuned performance oriented non-progressive 2bbl would operate well enough that the average rider would be hard pressed to feel much compromise, maybe a little at the pump. Carbs like Weber and Dellorto offer a great deal of tune-ability, even different size drop-in barrels to change the MM spec. I have little doubt that one could be tuned to work correctly on these machines, but not necessarily at a great savings over the OEM rack rebuild. I'm thinking that intake design is at least as critical as carb choice. It would be slick to design a single plenum upper manifold to bolt right to the OEM intakes.

 

As I'm typing I have a mental image of my Vmax with a pair of 36 DRLAs on a custom intake haha.

 

While I TOTALLY hear what your saying Case and am 100% enthused about seeing the testing and all that too,,, I still wonder though if a person who is mechanically inclined to the point of making the swap and dialing it in would also be entirely capable with a cheap set of gauges be able to, in about 20 minutes, dial in a good sync.. Dont get me wrong though brother,, I LOVE the whole modding scene but WOWZY,, if a person had to pay a custom shop to develop/build/tune/dyno a single carb setup I got a hunch they would be into some serious outlay... IMHO,, those joints dont work cheap..

By the way,, LOVE your take and thoughts on the V-Max!! Get er done and have some fun Case!!

 

[BlueSky]

No sync would be required with the one carb setup. the 4 intake runners are the same length and volume and there is only one throttle plate. And with one larger carb with larger fuel passages, it wouldn't be prone to plug up after sitting for a couple of weeks. Seems to me an exhaust analyzer would be necessary to make sure the carb is properly metering the fuel in all the rpm ranges and load conditions. Dyno tune would be the way to do that I presume.

 

I'm sure there is a good reason that all factory 4 cyl bikes that I know of have 4 carbs.

[bongobobny]

OK, if all 4 cylinders were exactly the same then there would be no reason to sync, but unfortunately, they are not exactly the same. There are minor differences in compression and other factors. I will grant you that they are relatively insignificant, but when you are trying to squeeze every ounce of power and efficiency then these factors do become somewhat significant.

 

Yes, there is indeed a reason why 4 bangers run 4 carbs...

[BlueSky]

Or the stock carbs need synchronizing because the plug up so easily that each one is in a different stage of plugging up and syncing them makes up for some of it. In the higher rpm range, the vacuum diaphragms may not be working the same and there is no way to sync that.

[Patch]

If anyone wants to design a new plenum then it requires an understanding in fluid dynamics, how one gets that is up to the individual.

You cannot just assume or take for granted that flows will arrive as wanted. There are restrictions inherent to fluids combined and the effects of distance traveled.

Your first challenge is to overcome throttle angles, then to achieve even flow to all ports, then volume then velocity depending on rpm range sought.

There is zero reason to bolt to existing intake piping if designing a new intake manifold.

Would anyone who knows think that CFI is better than MPI injection for economy or performance?

 

I'd like to remind riders that it is best to read compression before spending time and money on their carbs. This is a standard that is too often overlooked.

I knew of a fellow who ran a web forum that charged his members over 1200.00 plus shipping to rebuild there carbs. I asked him why he wasn't suggesting a compression test first? He replied what difference will that make!

So tell me how can you reason thru indifference?

All these gadgets we see and read about, really - just disregarding of the basics both in theory and good practices.

More and more we see questions asked not for factual experience to be shared but rather for confirmation after the fact.

[cowpuc]

Or the stock carbs need synchronizing because the plug up so easily that each one is in a different stage of plugging up and syncing them makes up for some of it. In the higher rpm range, the vacuum diaphragms may not be working the same and there is no way to sync that.

 

Or the stock carbs need syncin cause the linkages, bushings, diaphrams, vacuum hoses and even screws that control them are old, tired and worn out.. Just like some of the riders who those amazing fastest, most comfortable, reliable 1st Gens who haul them are:witch_brew:

[cptriker1]

I know that this must have been picked up from GL1200s. I know i wanted so badly to convert mine, but the carb was no longer manufactured and was impossible to find or get parts.

 

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[BlueSky]

Or the stock carbs need syncin cause the linkages, bushings, diaphrams, vacuum hoses and even screws that control them are old, tired and worn out.. Just like some of the riders who those amazing fastest, most comfortable, reliable 1st Gens who haul them are:witch_brew:

 

Old, tired, and worn out! I resemble that remark!

[cowpuc]

Old, tired, and worn out! I resemble that remark!

 

:thumbsup::thumbsup::thumbsup::thumbsup: