Help Drilling a Bing

I am going to drill out the Bing on my Magnum for an extra boost while I wait on a kit. I am a virgin when it comes to this so I have a couple questions.

Can I go as big as 15.5?

If so what is recommended Jet?

Should i drill the carb side of the intake as well?

I have pipe and air ready just need a little help before I proceed.

Re: Help Drilling a Bing

There is no recomended jet. You drill both sides. 5/8 inch drill is about 15.5. Take the emulsifier tube out first. Idle may be affected

Re: Help Drilling a Bing

your very likely to fuck it up. i know its wicked hard drilling aluminum intakes, carbs whatever from experience trying the same things you wanna do. buy a 15mm bing theyre affordable and very consistantly good.

Re: Help Drilling a Bing

if you really want to drill yours i recomend using a dril bit to do most of the work then go in with a DREMEL brand orange grinding stone and a lot of wd40. you need to smooth everything out really nice, and chamfer the inside the chamber along the edges of the newley drilled tube. these will be rough and wont let the throttle slide go up and down. BE VERY CAREFUL not to knick the little nipple on the side wall which guides the slide.

remember to take out the emulsion tube first, if you grind that down your carb will not run. it will be WAYYY too rich because you are effectively destroying the needles entire purpose.

you can buy a 15.4mm drill bit at home depot as well as the dremel bits.

WASH OUT THE CARB WITH BURNING HOT FAST WATER. you dont want any pieces of metal working their way into your cylinder.

Re: Help Drilling a Bing

here is a quote and pics from my last drilled bing. dont go this big, its the biggest i have gone before and i havent run it yet.

"heres the whole thread":

"i took a 12mm bing, ate a bunch of the meat with a tungsten bit on the dremel. then i clamped that shit down, and inserted a fucked up big orange grinding bit for the dremel. it has been used on lots of other projects so it was already in the shape of a cone. so i literally barely held the dremel over the carb body, and just let gravity do the work. listened to some music, smoked a cig and sprayed wd40 a shit ton. it came out soooo even and smooth. cant seem to take a good pic though.

i didnt hit into the float bowl or anything. i stoped just short of the slide chamber so technically its like 16mm on the air filter side. i just wanted to make sure air didnt get past the sides of the slide. the main jet emulsion tube has a groove added to direct flow to the intake manifold side. and i will be sure to do the "lil buddy" trick and drill a small hole on the side of the carb above the top of the tickler button. this allows a minute amount more air in at idle which helps with the richness in low rpms notorious to the bored bings.

the intake was fun. i used a franco morini stock header (which is 20mm) and reshaped it to fit at the right angle. i then cut about 1 inch off an existing stock 12mm intake, sanded down the skinny part till it slid right in to the negrini header. applied jb weld, let cure then bored with the same method.

im very excited to see how this setup performs. i really really would like the monza to be a daily driver, but shit, any motor thats reliable is too slow for such a fast looking bike. any motor fast enough to match the looks blows up. e50s wont work, i have to modify a za50 to even use that. the original motor is rare, expensive, and the dollar is fucked right now. so this should be the best of both worlds. hoping for like just under 50mph. good torque, keep up with traffic and… not blow up….

heres the pics! big but not too big.

Re: Help Drilling a Bing

Harold, do you have any pics of the "lil buddy" trick, or the groove in the emulsion tube? I'm not really sure how that would be made and how much effect it would have?



Re: Help Drilling a Bing

Can't tell you have easy this is with the right tools.

Re: Help Drilling a Bing

Very nice Paz,, tool, tools tools and such a deal too.

here's some that I did a while back.

1st Carb on the L was a 12mm, I did some boring to it and for reference, that’s a stock 14mm next to it on the R. The intake on the L is a Bored 14mm and the 1 on the R is a stock 14mm.

Air die grinder

Re: Help Drilling a Bing

if you are too lazy to chamfer around the slide passageway, you can take a craftsman 10mm 3/8th socket attached to a drill to ream out the edges. works well and the slide will move nice and smooth again.

Re: Help Drilling a Bing

Has anybody actually ran there Puch with the newly bored carb?

I would interested in the official outcome!!!


Re: Help Drilling a Bing

I bored one out to 16.5mm with a dremel, and it ran pretty well. I need a larger cylinder or a better pipe with it though.

Re: Help Drilling a Bing

running mine bored to 9/16" which is about 14.3mm on a stock 14mm intake cleaned up to same. Was ok on the stock cylinder with an estoril, now with a 65cc arisal it is much faster, but really rich and four stroking at idle. I would really appreciate more details on the 'buddy trick' hole. thanks!


Re: Help Drilling a Bing

figured i'd bump/update this: tried buddy trick hole on the 12 bored out to 14.3, helped a little, but not enough and i did not want to make the hole any bigger. tried a real 14mm bing and had same rich idle issue. fixed by dropping the needle jet/jet holder down from 2.22 to 2.17.

The bored out carb runs just as well as the factory 14, gonna try to go as big as possible without breaking through the thin area at the top of the bore by the choke slide. can you really go 5/8 without busting through there?

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