Intake manifold improvement

[ericheath]

Honda probably did have some logic when they went with the 1200 carbs because not only did they reduce the runner diameter and Venturi diameter by quite a bit, they also changed the angle of the carb as it comes out of the plenum. Stock 1000/1100 carbs are tilted only a few degrees , while 1200 carbs are a good 20-30 degrees tilted. This reduces the amount it has to turn in the elbows. The 1200 carbs were big on the inlet side and sped the charge considerably though the smaller Venturi, runner and valve. The 1200 redlined quite a bit lower than the early years, but I'm not sure of why that was.

I never looked into the ports of the 1200 heads to see if much was different there.

Seems as though the best documented changes to the intakes (short of forced induction) were to put them straight up with dual Webers on top.

The veterans are probably right, but the forum is dry here in midwinter, and I'd love to see what you could come up with.

There are more than a few who feel the single carb can produce good results.

[ericheath]

Going to add this with a disclaimer to the numbers--going by memory which isn't what it once was. It's getting crowded in there. I just posted this on a different thread, but maybe it's pertinent. The 1200 carbs did go back to 32mm or maybe they were both 34mm , on the inlet side of the carb, but reduced the venturis to 30mm and elbows and intake valve (I think) by quite a bit. I believe this was to cram more in at lower rpm using speed rather than volume, but this gives a little up at higher rpm.

I have some elbows that measure over 36mm where they go into the head. I have about 50 elbows and they are quite different in their measurements. Most 1000/1100's were 34-36mm, while the 1200's were 30mm.

Some gains might be made by evening out the transitions from the carb exit downwards. Seems as though they have an uneven tract and may even vary from bike to bike.

[Gator417]

Yeah, Honda designed this engine in 1973 and since then there has not been one solitary thing ever discovered about induction, airflow and carburation.
The intakes are part of a well designed and very balanced system. You can definitely find gains there, but they'll be limited by the other parts of the system. To get substantial gains, you'll have to make complementary changes to other parts of the system (exhaust, cams, valves, ports etc).
So my vote is take the skills, talents and knowledge you have and apply them wherever you want. Just don't let a bunch of washed up keyboard heros tell you it can't be done because they are afraid to try it.
Gator
PS; make sure you keep the forum up to speed on your efforts and results. Even if its a fail, we'll all appreciate the try.

[CYBORG]

washed up keyboard heroes??????????????

[77Gowing]

I don't have enough MC experience to ever have been washed up. I'm still washing down on my lessons.
BTW wouldn't "Elbow Grease" help the flow velocity?

[gltriker]

deleted by me

[CYBORG]

We all know who we are...........who we think we are.............and who we want others to think we are. But others usually know who we really are.

[5speed]

never say never. go for it..

[robin1731]

washed up keyboard heroes??????????????

Wow, right???!!!!!

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