Another carb question

[Dusterdude]

Im considering using a side draft harley type carb on my 1100,if i do this,what size carb should i use?most harley carbs are 38mm,is that too large?thanks

 

[slabghost]

I've no idea how others size carbs. My habit has been to look at the cc of the machines and the typical rpm. 1100 cc V twin typically runs at a lower rpm than an 1100 four. So I'd look for a carb from a V twin in the 2000cc range. Whatever size they use is where I'd start. But this is all just my limited understanding and totally without scientific backing.

 

[Dusterdude]

That makes sense,who might build a 2000 cc vtwin?thanks sg

 

[82a]

https://www.google.ca/search?q=honda+18 ... 12&bih=835

https://www.google.ca/search?q=Suzuki+1 ... 12&bih=835

 

[Dusterdude]

Thanks 82,ill check it out

 

[Dusterdude]

Another thought ive had is,since the carb is only feeding one cylinder at a time,which on the 1100 is 275cc's,im thinking the carb should be the same size as a 275cc single cylinder engine.thoughts?

 

[backlander]

Old rule of thumb from my hot rodding days was you needed 140 cfm per every 100 hp your engine could produce. Here's a cfm calculator where you can feed your info into and it will give you an approximate size carb needed for your application.https://www.csgnetwork.com/cfmcalc.html

 

[Dusterdude]

Thanks bl,how much hp does an 1100 produce?

 

[backlander]

My spec sheet says it's government rated at 81 hp.

 

[Dusterdude]

Groovy,thanks

 

[Ansimp]

Dusterdude » Mon Nov 04, 2013 7:49 am[/url]":1wqfkkwk]
Another thought ive had is,since the carb is only feeding one cylinder at a time,which on the 1100 is 275cc's,im thinking the carb should be the same size as a 275cc single cylinder engine.thoughts?

It would be feeding one cylinder per one revolution. Carby volume needs to meet the engines capacity as a pump ( what volume of air is moved) so your 275cc single carby would not be adequate

 

[Dusterdude]

Ok,so i would need something that could feed an 1100 cc engine?

 

[slabghost]

Yes. While one cylinder is firing the carb is feeding a fuel charge to the other three. Kawasaki I know has some big V twins. Not so sure how big the Honda or Suzuki V twins are.

 

[Dusterdude]

It seems the suzuki twins at least are using two carbs,ill have to look into the kaw and honda twins

 

[slabghost]

Most bikes use 1 carb for each cylinder. However. I've seen where some have built manifolds and used just one of the two carbs. That said I think one carb off a 1600cc or larger V twin should be close enough to work if jetted right.

 

[Dusterdude]

Cool deal sg,ill see what i can find from one of the big v twins

 

[OldWrench]

your carburator should be between 117 and 130 cfm. Then you also need to worry about jet size or you could end up running too rich or too lean.

 

[Dusterdude]

Cool,seeing how bike carbs are rated by size,any idea on how to figure cfm?thanks