Carburetor 4-Way Crossover Equalization Manifold

[Pat Conlon]

Hey folks, look what I found over at the FZ1 Forum.
Remember last month that new guy's question about why the PO hooked up the FJ's vacuum ports to hoses connected those to the adjacent carbs?

David, Randy, Frank and others...I would like to hear what you think about this...The Gen 1 carb'ed version of the FZ1 uses a CV type carb, like we do...

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Carburetor 4-Way Crossover Equalization Manifold

The Carburetor 4-Way Crossover Equalization Manifold is a simple assembly of hoses, T-connectors, and hose clamps which is placed over the existing vacuum spigots between the carburetors and engine. These spigots are normally capped with rubber covers which are removed only when performing a carburetor synchronization.

Credit for introducing this idea goes to the creative Mr. Bill Jinks of the Owners Association.

Theory:

The idea is to connect the carburetor outputs/engine intakes for the purpose of:

Balancing out the vacuum impulse demands between the carburetors.
Equalizing the vacuum variances of each individual cylinder's intake strokes.
Normalizing any air flow variances between the carburetors.
Slightly increasing the amount of fuel/air charge available by providing each cylinder access to all four carburetors thereby increasing the effective size of each carb.
Another theory, from MikeGTX: As each pair of pistons (1&4 and 2&3) rise and fall together, one is on the induction stroke and the other on the firing stroke. So, one set of inlet valves only is open at a time. The mod connects two inlet stubs together, so as the induction stroke of one cylinder takes place, it is able to draw through the link pipe as well as it's own carb. My theory is that the additional flow through the vacuum stub creates a bit of swirl in the inlet air flow itself. This could help to hold larger fuel droplets in the charge, rather than them falling out onto the inlet tract throat. Tuners sometimes modify the heads to induce this kind of swirl a bit further downstream as a means of helping to fill the combustion chamber more efficiently.

I am admittedly not a carburetion theory expert so I can't attest to the validity of these ideas. Preliminary testing with clear crossover tubing did reveal the presence of raw fuel droplets forming in the hoses indicating true crossover functionality.

Benefits:

There is anecdotal evidence from those who have tried this that the following benefits are real:

Easier cold starting.
Better mileage.
Reduced vibrations and smoother running.
Improved low rpm performance and responsiveness.
I cannot attest to the first two items above because my cold starting has never been a problem and I have not done any fuel mileage comparisons. However, I can vouch for the reduced vibrations and the improved low end response.

I had a 6500 rpm buzz made quite noticeable by the poor vibration isolation characteristics of the solid rubber feet on the Fatory Corbin seat. After installing the Carburetor 4-Way Crossover Equalization Manifold this buzz was reduced to a slight tingle. After installing the manifold, snapping the throttle open quickly from a steady 2500 rpm (about as small a throttle opening as I can get) in 1st gear results in a lifting of the front wheel.

There has been an actual before and after dyno test done on a bike with stock jetting and no benefits were found as measured by power and torque curves. Benefits in terms of smoothness and throttle response are difficult to quantify but, theoretically, the manifold may produce some improvements in those areas. Nevertheless, the manifold will not perform at its best for stock jetted bikes and is not recommended in that application.

Dynamometer results of a rejetted bike with the manifold attached has confirmed an increase in torque averaging 4 to 5 lb-ft up to about 4000 rpm with a 7 lb-ft boost at 2700 rpm.

Parts:

To make the Carburetor 4-Way Crossover Equalization Manifold, you need:

Two feet of high-quality flame resistant fuel hose, 1/4" inside diameter. A recommended product is "Gates LOL Plus 4LOLC+ Flame Resistant Nitril Hose." I found fuel hose at Orchard Supply Hardware marked SAE J30R7. 1/4 inch hose is used rather than a tighter spigot fit 3/16" to provide a higher flow rate for the crossover of vacuum pressure and air/fuel charge. As long as a supple material is used, the hose clamps should provide a suitable seal at the joints.
Two one-piece barbed 1/4" Brass 'T' Fittings. Do not use piece together fittings. Also, do not use plastic vacuum T's, they are not fuel rated and will not hold up to the heat.
Ten 5/16" - 5/8" Stainless Steel Hose Clamps. A Marine Supply store will carry fully stainless clamps. Be wary of those where the worm screw portion is plated low quality junk.
The cost of these items should be about:

Fabrication:

To make the Carburetor 4-Way Crossover Equalization Manifold:

Cut two end sections of fuel hose 4 3/4" in length
Cut two center downtubes 2" in length.
Cut a center tube section such that there is a 3 1/8" center to center distance on the brass T's. For me this was a tube length of 2 3/4". Depending on the style of T's you get this length may vary slightly.

Update:

Bill Jinks now recommends an simpler manifold as an alternative. Use two lengths of hose to connect cylinders 1 to 4 and 2 to 3 separately. The benefits from this setup may be nearly equal to the more complex four-way manifold. It also has the benefit of eliminating all the connections made necessary by the 'T' connectors and the additional potential of air leaks.
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Taken from here: http://www.cartestsoftware.com/fz1/carburetorequalizationmanifold.html

[Harvy]

I've got some 6mm fuel injection hose kicking around somewhere........ I will give this a go.


Harvy

[SlowOldGuy]

It's a load of bullshit and a waste of time.

Any improvement they got was from adjusting their carbs and probably synching them at the time they installed this "mod."

On the '82 XJ1100 head, Yamaha had their YICS ports which did this exact function of connecting the inlet tracts.  It also was supposed to add "swirl" to the intake charge and thus promote better combustion.

Not sure how well it worked, but it made it a bitch to sync the carbs because it required a special Yamaha tool to plug the ports to isolate the intakes for an accurate synch.

The early FJ heads included this "feature" on their heads.  It can be seen just below the intake runners.  However, in testing the "new" 4 valve head on the FJ, it actually hurt performance.  So, in production, the channel was never drilled.  This part of the head casting was eventually eliminated on a later model, not sure what year it was deleted from.

This "technology" rates right up there with the intake fan blade that supposedly rotates the intake flow (didn't work as advertised) and there was also a special kit that plumbed air from the air filter to the 4 main air bleeds (into the emulstion tube/needle mixture) with adjustable flow so you could "equalize" the flow to all the carbs (it also lived a heavily advertised and short life).  Finally, there was the "Dial-a-Jet" (ask TRoy about his experience with these devices).  The DaJ stole fuel from the float bowl drain screw and delivered it to a needle which you stabbed through the intake rubber.  It had a valve with multiple settings to control how much extra fuel you could add to the intake mixture. Good idea in theory, but a well thought out set of jets and needle shims (or a good carb kit) would kick its ass for a fraction of the cost.

My recommendation is to stick with the basics and let this roll on by.

DavidR.

[racerman_27410]

Bill Jinks had a lot of ideas.. some of them were really good.

I actually have one of his FZ1 fork braces on right now..... his design was functional and nicely executed.

However i would concur with David on this one......ixnay on the extry plumbingnay 


KOokaloo!


Frank

[Pat Conlon]

 Interesting history on Yamaha YICS,  thank you David and Frank!
I should have run this by you first before wasting the bandwidth on this forum.

[Flynt]

I would like to hear what you think about this...

Hogwash plain and simple...  although to your point, I'd bet that's why the hoses were found on the intakes.  People will do stupid shit based on rumor sometimes.

Best case IMHO is no degradation results from introducing unmetered air into the system (think about 1 cyl trying to get the right AFR out of the carb...  to fine tune you route in some other AFR in a completely minuscule amount).  As you open the throttles, the relative effect of these hoses would be reduced since you have so much more flow through the carb.  At low throttle plate openings and higher vacuum levels in the intake plenum, you'd get max flow through those little nipples connected to a longish hose leading to another high vacuum environment...  that will still be ~0.  Pure snake oil.

Worst case is you actually do cause some level of AFR mismatch (hose falls off or breaks) and you burn a valve due to lean conditions.  I'm calling this one a hoax and a bad idea at that.

Frank

[fintip]

I was just about to say that this sounded exactly like the YICS... Which, when asked in '84 why they didn't include it on the FJ, they responded that it had never been intended for engines of this level of power. (Which sounds like bullshit.)

It wasn't that hard to sync carbs with it, you just had to have the 'tool' (a metal rod with spacers) that you removed one bolt to slide into place. No biggie. Easy to fabricate, if you didn't have the tool. They can still be found relatively cheaply on ebay. The XJ650 was produced with and without YICS, and I always imagined that there was a difference and preferred the YICS engine (I owned and rode both).

But as stated above, I'm sure there's a reason Yamaha chose to ditch the idea and not use it on the FJ.

Makes you think, though, they must have tried it on at least one prototype engine... Surely there's some FJ engine out there with YICS drilled out into the head, no? Wouldn't that be a find?

[mr blackstock]

I own a Yamaha XJ650 1982 with YICS, and I can attest that synching the carbs without the YICS "blanking off" tool is only half the job.  The bike will run fairly well, a bit too much vibration under speed, but synching the carbs using the YICS "blanking" tool improves the balance very noticeably!
So I have no idea if the manifold idea works, but the principle works really well with the XJ series of bikes.

cheers, Gareth

[motohorseman]

What about running hoses from the synch ports into an adapter that puts all of the hoses into one - it comes up under seat and into your arse, when you pass gas, there is an extra power boost.

Anyone want to be the first to try it?

[rktmanfj]

What about running hoses from the synch ports into an adapter that puts all of the hoses into one - it comes up under seat and into your arse, when you pass gas, there is an extra power boost.

Anyone want to be the first to try it?

Carey would be the obvious choice here...       

[FJmonkey]

That could solve the eye watering problem while wearing one-piece leathers.... 

[fj11.5]

problem solved, monkey is now a guinea pig  or a lab rat, , if the ranger leathers can be fitted with a power port

[FJmonkey]

problem solved, monkey is now a guinea pig  or a lab rat, , if the ranger leathers can be fitted with a power port

But another problem created, picture this..... A long line of cars in front, blocking the Kookaloo, no cars coming the other way, the corner may be hiding opposing traffic (how much time/room do I have to pass?), I feel boost building.... Will it be slow and steady like good roll-on power, or a "Holy F%$# SH&^%, hang the hell on" second stage rocket booster that makes roads obsolete?

[fj11.5]

ahhhh thats why you should always stay 2~3 seconds behind,  allows room to manouver