Other poll : should I Bore carbs to larger size

is it worth boreing the 44mcarbs to larger 46mm size

  • Total voters
    9
  • Poll closed .
yama-doo

yama-doo

X-
Location
Port Saint Lucie Florida
I have three 44mm mikuni's going on a Yamaha NP 1200, is it worth boring them a little larger while I am rebuilding , I can go to 46mm easy , 48mm gets close clearance to the set screw in the bottom of the carb and 54mm would take the set screw out and be real thin sides walls . Anything over 46mm I have to bore the base plate also.
 
TheBuzzard

TheBuzzard

Location
the jetski grave yard
how are you going to bore the carbs, with a dremel? all 44/46s that get turned into 48s or bigger, get the venturi taken out and replaced with an aftermarket one after boring. if this is some hillbilly mod you are trying, i wouldnt.
 
yama-doo

yama-doo

X-
Location
Port Saint Lucie Florida
hey come on hillbilly mods are the best :)

no a dremel is not a real tool :eek: I normally bore AC cases on the mill but would probably be easier to bore these carbs on the lathe
 
Last edited:
TheBuzzard

TheBuzzard

Location
the jetski grave yard
and a set of replacement carbs when you ruin the ones you tried to modify for some silly reason........... if you dont like my advice, go with 102nd7 and be sure to tell us what really happened, so we'll know what not to try.............. edit: sounds like you got some good equipment, but that aint always enough.
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
Todd LeChance use to reverse bore 44's where he bored the bottom side to 48mm below the butterfly. That is an easy job. It worked good on single setups.
 
TheBuzzard

TheBuzzard

Location
the jetski grave yard
i never said it was silly to go bigger carbs. i have 48s on everything. 701s included. i think its a silly idea to try and modify your carbs yourself, unless you really know what you are doing. i'm about ready to say what i never say. "do it and let us know how it turns out"
 
yama-doo

yama-doo

X-
Location
Port Saint Lucie Florida
TheBuzzard ,
Come on man I don't know what you issue is ................. the posted question never was about my machine work capability and even tough it is a completely separate subject don't really see how it is relevant to send them to another machinist

The question is simple: is there enough noticeable difference in bottom end or top end to make it worth wild going to larger diameter carb if you can answer "yes it does" or "no it doesn't" great , other wise please go harass someone else
 
yama-doo

yama-doo

X-
Location
Port Saint Lucie Florida
102nd7
I apperactice your earlier straight forward answer somehow every one is stuck off topic on the machine work . yes I have extra carbs (linkages is another story), not concerned about being able to bore the carb just weather there is a noticeable difference to make it worth my time
 
kevbo

kevbo

Location
dfw
yama-doo said:
I have three 44mm mikuni's going on a Yamaha NP 1200, is it worth boring them a little larger while I am rebuilding , I can go to 46mm easy , 48mm gets close clearance to the set screw in the bottom of the carb and 54mm would take the set screw out and be real thin sides walls . Anything over 46mm I have to bore the base plate also.
Click to expand...
A stock 44 is already plenty for that application. A larger carb will tend to accelerate slightly better but also go rich sooner so top rpm remain flat. You can compensate by setting the pilot much richer and power tuning the top screw for a slight rpm increase. Problem with this is fuel consumption at part throttle will be up 30%. If you do cut the carbs your jetting reference is lost so monitor each cylinder carefully when setting the top screw. If you want to make something bigger look at the exhaust port.
 
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