Boring out carb?

[dparenti13]

Would boring out a carb have any performance benefit, top end or low end? You would obviously have to rejet. I'm running a dellorto sha 14mm clone, just curious if this would have any benefits boring it out, or if it's even possible.

 

[JerboaJohn]

sure you can. but it'd be easy to go too far.
more flow is mostly top end gains but since 14mm is puny you'd get whole rpm range gains going to 16 along with a hi flow air filter

 

[JerboaJohn]

unless you're screaming 8000+ rpm, racing, have a pipe n gearing, a 16mm carb is all you need and it's good for all the other upgrades youd do in the future, tho for spec on tuning across the board, SHA clones kinda are lacking. I have one and it's ok. I took it out to 15mm bcs I run a 48cc and trying boost only low end so I keep everything a little smaller than ppl with 66cc's that want to go 45mph+

 

[dparenti13]

Forgot to add that I have RSE reed valves and a windowed piston, does that change anything?

 

[dparenti13]

Also I'm assuming with the bored out carb to 16mm I'd have to jet richer too?

 

[JerboaJohn]

yeah more air in = more fuel needed. 2 sizes bigger would be ballpark close. not too sure about reeds in the equation.

 

[CrazyDan]

Got to make sure that you don't go full bore removing the venturi effect. The carb needs that slight pinch where the main jet enters the air stream.

 

[Frogslayer]

That's what creates the vacuum to pull the fuel out of the bowl and through the jet

 

[dparenti13]

How should I go about boring the SHA 14mm dellorto clone to 16 or 17mm?

 

[mark20]

How should I go about boring the SHA 14mm dellorto clone to 16 or 17mm?

since you have a reed, i would go for a 18mm mikuni carb (clones if you low on $)
yes its possible to bore the carb, but dont go to far. i would start at 15mm and work your way up.
its risky, but it would be worth it!
also, you gain top end but loss some low end. (try blowing a piece of paper normally, then do it with your mouth wide open, thats like boring the carb out)
boring is a touchy subject, i would go on youtube and look up how tos, and go from there