Boring carbs?

F

fusion 69

VIP Member
Joined
Jan 15, 2009
Messages
240
Age
53
Location
ohio
Would I gain much by boring my carbs? I run drags only, grass and ice, have some mods done, just thinkin a little more fuel might help her out.
 
I've got a set of 38mm flats from a mach I'd sell. I was going to run them on my 780 motor, but never got it done, and it runs well enough for how I use it. I picked them up a couple years ago, tossed them on the shelf and never looked at them again. No idea what's in them for brass as I've never opened them up. I'd take $110 shipped to you.
 
Fusion - If fuel is all you wanted you could increase your jetting. I think it's air that you are after with a larger carb bore size. I'm no authority on the subject but feel that you would only need more air if certain changes required more air.
If you raise compression and or bore size more air certainly benefits combustion.
If the comp or bore have not changed you will loose vacuum signal which causes other problems. The velocity or speed at which the fuel flows through the carb. If you go to a larger carb the air speed slows down. The smaller 33mm Yamaha carbs keeps velocity up and keeps the vacuum sharper making the incoming fuel droplets break up and atomize into a better finer air + fuel fog. The smaller the fuel droplets the better the combustion.
 
I have a set of bored carbs- 35.5 mm that i ran for a while this season. I liked them, ran good. I am going to switch back though due to the loss in fuel milage on the trail. They definately ran better on top than the stockers.
 
tedgoesfast said:
get them tapor bored you dont lose throttle response
Click to expand...
Taper bore is the key dude, I had the opportunity to work with a flow bench expert at General Motors... He found the the right angles to bore them and passed that info to me... I would suggest a at least 40.5mm carbs
 
I read a pretty interesting article in American Snowmobiler earlier this snow season. It might be worth reading. If I can find the article maybe I can post a link if anyone is interested in looking at it.
 
glockwise said:
I read a pretty interesting article in American Snowmobiler earlier this snow season. It might be worth reading. If I can find the article maybe I can post a link if anyone is interested in looking at it.
Click to expand...

I have that issue. It was/is an interesting read.
 
have dyno tested motors w/ bored carbs. sometimes they make a few more h.p. & sometimes they don't. unless your building a motor to specific class rules you would be better served to use stock bore larger carbs. they're less fussy. bigger carbs will flow more air...but maybe your motor doesn't need that?? the only way to find out for sure is to dyno test. anything else is guessing.
bob
 
You must log in or register to reply here.


Back
Top