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2 into 1 carb mod

  • Thread starter Thread starter System9
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System9

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Anyone ever do this on a twin GS? I've seen it done on other bikes, and the gs450 would work well since the frame has no spine, you could center the single carb with no obstruction (-the airbox)
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Its getting there;) Would a speed decrease be the only change? Would you gain torque, and lose top end? Or just lose speed all around? I use mine for city commuting mostly, fastest speed limit is around 45
 
That is called a siamese port and is an excellent way to give away power. If you ever rode a Honda CM400 you would probably be in its territory with that downgrade.
 
Thanks koolaid, I definitely don't want to lose significant power, I've just been reading yamaha forums where supposedly its done with no power loss.
I actually have a cm400 in my garage too. Its my son's, was this a mod people did to those bikes?
...ahhh, i see. cm400 = slow, like my brain with lack of sleep :-)
 
System9 said:
Thanks koolaid, I definitely don't want to lose significant power, I've just been reading yamaha forums where supposedly its done with no power loss.
I actually have a cm400 in my garage too. Its my son's, was this a mod people did to those bikes?
...ahhh, i see. cm400 = slow, like my brain with lack of sleep :-)
Click to expand...
Yup, I can hear them barking from two blocks away.
The most efficient way to flow the air/fuel mixture into the cylinder is to allow each cylinder have its own carb, which is why all real motorcycles have this configuration.
 
using a 2 into 1 inlet /for 1 carby

using a 2 into 1 inlet /for 1 carby

hi, guys on the xs650.com site its reasonably regular that guys are using joe wiseguys system 2 into 1 ,, and most are rejetting the single carby are running great its well worth a look at his site as well regards oldgrumpy :)
 
1971 Triumph T120R throws out 49 bhp @ 7500 rpm, a Trophy from the same year makes 45 bhp @ 6500 rpm. T120 has 2 carbs and the TR6 only 1. Apart from the obvious head mods the engines are the same and chassis differences are only really cosmetic.

At low revs there's nothing between the 2 bikes but wind them open and it's light and day.
 
Don't do it on a 450 or any other Suzuki twin...The examples quoted where it has been done successfully are all 360 degree cranks ie even firing intervals. The Suzuki is a 180 degree crank ie uneven firing intervals.

In practise this means one cylinder is short changed of mixture.
 
What GregT said. single carb +180 deg crank= dog.Probably get better gas milage though.
 
its been done, you will need a big enough carb for air flow, but i dont see why it wouldnt get good gas milage, in reality,prolly have more top end than bottom, if carb is on the small side
i know its a 2 smoker, but yamaha banshees have them and they run great!, so if your home work is proper it should work, the crank issues ,are limited by the cam, intake,exhaust, and duration anyway
 
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