Carb Confusion / Selection ---Hemi Predator

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SeanO

New Member
#1
#1
I see the aftermarket or modded carbs are available in .615, or bored to .625 etc. With a digital caliper, the engine side of my stock Hemi carb measures .745 or 18.9mm. What am I missing?
I'm replacing a 120cc 4.5hp yamaha engine (kids snowmobile) that currently uses an 18mm carb which is .708, Still larger than the modded carbs.
I'd like to keep the 18mm because of the throttle and choke configurations. Without the factory choke set-up, I'd have to lift the hood in order to flip the choke lever.
I plan on leaving it governed for now, & will do the proper upgrades when the time comes to make more power.
So I guess to boil it down...Is 18mm larger than the modded carbs (again, am I missing something?) And, can I make good power in the future with the 18mm ungoverned?
Thanks
 
S

SeanO

New Member
#5
#5
So a .625 bored carb would be considered @ 16mm then? The 18mm factory carb I have is the size listed in the owners manual (not measured on the head side) So I'm thinking its still gonna do OK when jetted properly.
Thoughts anyone?
 
Y

youngengines

New Member
#6
#6
As stated, the venture is the restriction. A larger butterfly can be installed as well, but for most builds its not necessary. With that said, even a AKRA legal stocker engine will make more power with a larger venture carb. (I like a .650 in most mild cases)
 
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SeanO

New Member
#7
#7
youngengines said:
As stated, the venture is the restriction. A larger butterfly can be installed as well, but for most builds its not necessary. With that said, even a AKRA legal stocker engine will make more power with a larger venture carb. (I like a .650 in most mild cases)
Click to expand...
So if .650 is 16.5mm, do you feel the stock 18mm or .708 carb should be fine for a stock 212cc? Again, I'm going to leave it
governed(for now) being the stock 120cc is rated at 4hp. I also have an adjustable jet & velocity stack for the 18mm.
Thanks for the help.
 
Y

youngengines

New Member
#9
#9
SeanO said:
So if .650 is 16.5mm, do you feel the stock 18mm or .708 carb should be fine for a stock 212cc? Again, I'm going to leave it
governed(for now) being the stock 120cc is rated at 4hp. I also have an adjustable jet & velocity stack for the 18mm.
Thanks for the help.
Click to expand...
If your not doing much modifying, the stock size hemi carb will do fine (jetted correctly)
 
Badlands

Badlands

New Member
#10
#10
I have the answer you are looking for... YES your 18mm carb will work, however you may need to re jet it.
 
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