1-2 intake

[bonesaw]

Thinking of making a 1-2 intake manifold for my xs.

Anybody have any pros/cons about this?

I'm curious if anyone's done it with a similar setup to my bike and how it ran/worked out.

Spec:
80 xs650
750 bore
Performance cam
Pamco Hall effect
HHB Pma

 

[figure8]

Hey, I know you! Lol. Some guys complain of inconsistency of fuel to the cylinders, but when set up right it takes some of the guess work out of carb issues such as being in sync.

I'm going to be using a 1-2 manifold if I ever get mine finished, lol. Good to see you on here, didn't know you posted here.

 

[bonesaw]

Thanks bud!

 

[fredintoon]

Hi bonesaw,
entering "single carb inlet manifold" in the search box gets you 29 hits, so, yeah.
From my experience with '50s & '60s vertical twin Britbikes, swapping intake manifolds to run a single carb instead of dual carbs gives you a little less top end power and a bit more mid-range grunt.
Mind you, those bikes could all run symmetrical manifolds while you can only do that on an XS650 if you go without an air filter or modify the frame.

 

[Shenanigans]

Joe wise guy sells them. No frame mod needed from what I can see.

 

[hooser]

As long as the intake are of different lengths there almost no way to match the flow to each cylinder. learn how to sync your twin carbs.

 

[fredintoon]

Joe wise guy sells them. No frame mod needed from what I can see.

Hi Shenanigans,
yeah, you are correct.
That's because Joe's 1 into 2 intake skews the carb off to one side so it don't interfere with the frame's central downtube.
Which means the manifold's inlet tracts can't be the same length.
Which in turn means the shorter inlet tract has to be more restrictive than the longer one to balance the two inlet flows.
And that'd take more time, skill, flowbench and die-grinder work to get right than they could afford to put into the product for the price they are asking.

 

[FLEA]

bloke in queensland is setting up a 2-1 (a enforcer ,wiseguys ,which I sold him ) with a tubo of his design (hes build a few tubos in the past so he knows what hes doing ) ..its for his drag bike which they are already using..should be intresting ,a bit of useless info but will update as he goes along

 

[Shenanigans]

Hi Shenanigans,
yeah, you are correct.
That's because Joe's 1 into 2 intake skews the carb off to one side so it don't interfere with the frame's central downtube.
Which means the manifold's inlet tracts can't be the same length.
Which in turn means the shorter inlet tract has to be more restrictive than the longer one to balance the two inlet flows.
And that'd take more time, skill, flowbench and die-grinder work to get right than they could afford to put into the product for the price they are asking.

There is another thread on this topic at http://www.xs650.com/threads/2-into-1-intake-manifold.49/page-2
Joewiseguy answers with this:
half an inch of travel diff between cylinders? atmospheric pressure at 14+lbs per sq inch? hmmm maybe a .00000000000000293 diff? seriously an offset intake with slight diff in length is not going to effect the bike. what will effect the bike is two carbs not in complete sync and with a differring fuel to air mix. one cyl hot from lean mix. and if it were that big of a deal i guess all the car manufacturers got it wrong. ever see the intakes of small block chevs and fords? some runners differ as much as 4 or more inches. doesnt seem to matter there either... you can set a single carb directly even between the cylinders but i prefer to not rebuild my bikes backbone and make frame mods when i can get great results with a slight offset. the tradeoff is not worth the work and expense of frame mods.

I dunno, but I'm thinking about buying one with his pretuned carb.

 

[fredintoon]

Hi Shenanigans,
well, maybe Joe did flowbench his prototype and maybe the different intake lengths don't matter a lot but for sure you don't need to balance carbs if there's only one of them.
But you are mostly going single carb for how it'll look on your build so yeah! Go for it.