Porting and polish 850 head

[Nessism]

The fun part there is that the 850 came with 32mm carbs, not 34.

Not sure where he got his info on the 34 measurement.

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I believe this is correct. Only the 1000 & 1100 used the BS34's.

[Guest]

[ATTACH=CONFIG]42959[/ATTACH]

sorry, here's the pic I meant to upload instead, best thing is I only have $300 invested in the 2 sets of carbs, that includes 4x new OEM carb bowl gaskets, 4x new OEM cover gaskets and a set of Robert Barr's o-ring kit.

In the pic your carbs are a couple of mm smaller than your intake manifold. That's not a good thing and will hurt the preformance.



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[Guest]

I believe this is correct. Only the 1000 & 1100 used the BS34's.

Maybe his bike had a 1000 head installed on it before he bought it

[Guest]

One-Civic
what is the measurement on your intake port side to side? Guessing at about 32mm

[one_civic]

I'll try and get a better pic but no, the intake boots match the carb intake perfectly

[Guest]

I'll try and get a better pic but no, the intake boots match the carb intake perfectly

And how do the intake manifolds match the intake ports

[one_civic]

Intake manifolds also match the intake ports, when I get home I'll measure with my digital vernier caliper and take pics

[Nessism]

Just to be clear...

Suzuki installed BS32's on 1980 and later 850's. one_civic's bike may have 34's installed, but the bike didn't come from the factory that way.

[one_civic]

so here's the verdict, cylinder intake port 34mm,

[one_civic]

I don't know why the pics are upside down when their right side upon my computer but, oh well

intake manifold boots 32mmIMG_0869.jpg

[one_civic]

IMG_0867.jpgvm29ss carb intake 33.5mm


A friend gave me this 850 engine with no tensioner or carbs, only the intake manifolds, so I don't know which carbs it originally would have came with.

[Guest]

With a 34mm intake port you want 36mm carbs for your best preformance. You can go as small as 34mm carbs but anything smaller will hurt the preformance of the motor. If your carbs are smaller than your intake port the when the fuel and air enter into the intake port and it expands and loses velocity the the air and fuel start to separate hurting power.

to get your carbs and manifolds to work to give you the best preformance you need to bore the carbs 1mm larger and blend the rubber manifolds carb side to the carbs and head side to the head.
I not saying it's not going to run good with the stuff the way it is but it will hurt the the preformance.



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[boris.h]

Sorry I do not agree with the last answer.... for me, if intake ports are 34mm (not the valves diameter!), the carbs may end at 34mm, and also for the boots (even if you have to enlarge inside diameter of them). I agree with the fact that the speed has to increase all the way, but there are already one decrease of diameter inside the carb (to get fuel = venturi), the other important decrease of diameter is at the valve... the most important at the carbs / head interface is
- no "step" between diameters of elements
- no "increase of diameter"

[one_civic]

IMG_0876.jpg

Here is a better picture looking through the intake side of the flatslide carb, it restricts down to 32mm at the intake manifold side. I may take 1mm off around the circumference but am wondering how much material needs to be left for an airtight seal at the o-ring? either way I'm better off with the larger 34mm 850 intake port head compared to if I wanted to use my stock 750 head.

[one_civic]

IMG_0874.jpg

and one looking from the intake manifold side where you can see the 29mm offset intake throats on the airbox side