Video request of pilot drilling

[o2jmpr]

Does anyone have a video they could share of how to drill out the pilot jet on the stock PZ30? I know a few of you have done it but I've never seen it done. They way people speak of it, it seems there must be some level of risk in ruining the jet/carb.

[cbrfxr67]

i just use my carb jet drills and slowly, by hand, drill it out to the size i need. I go slow and if it binds, back off and start again. Works for me,...

[Megadan]

Yeah, there isnt much involved, just go slowly and keep the bit straight. Like cbrfxr stated, if it binds at all, back offf and try again. The bits are very thin and will break easily.

[o2jmpr]

That easy huh? I thought there was some voodoo required or something. So just remove the jet, carefully drill by hand and clean before reinserting. I assume it’s soft enough brass that this isn’t too difficult to do by hand?

[Azhule]

Originally Posted by o2jmpr

That easy huh? I thought there was some voodoo required or something. So just remove the jet, carefully drill by hand and clean before reinserting. I assume it’s soft enough brass that this isn’t too difficult to do by hand?

If you need to use "Voodoo", some choose to call upon the "Drill Press" spirits to make sure it's drilled as straight as possible

[Megadan]

Originally Posted by Azhule

If you need to use "Voodoo", some choose to call upon the "Drill Press" spirits to make sure it's drilled as straight as possible

This is the voodoo that I do. Rotary tool drill press stand with a hobby clamp.

[o2jmpr]

Thanks you guys. I’ll go find some bits and give it a whirl.

[roundhouse]

I need to do this as well. What size bit?

[Weldangrind]

Buy an index of numbered bits from 61-80. Know right now that the bits will not necessarily be in the correct compartment of the index, so you need to measure the bit with at least a vernier caliper before drilling.


When you select an index, buy one that comes with a pin vise. A pin vise is a device about the size of a Sharpie with a collet in one end, to hold the bit. If you don't have a suitable way to hold the slow jet for drilling, you can just hold the jet in your fingers. Slowly and gently spin the jet onto the bit that you're holding stationary in the pin vise. With patience, the bit will find its way into the jet squarely and ease the hole open.


Back to measuring: insert various bits into the stock slow jet until you get a sense of which one is a close fit. Measure that bit and then search for one that is one size larger. Continue in that fashion, one step at a time, until the desired size is attained. The reason I prefer Mikuni is that jet sizing is tied to millimetres; a 25 slow jet is 0.25mm, so it's easy to make incremental steps without much fuss. A similar process with a Keihin jet requires a cross-reference chart to convert Mikuni (or millimetres) to Keihin.


I've followed this process several times with good success. When purchasing a cheap 61-80 index, it pays to buy two at once. That way, you're more likely to actually have a complete index with several spares.

[Megadan]

Originally Posted by Weldangrind

Back to measuring: insert various bits into the stock slow jet until you get a sense of which one is a close fit. Measure that bit and then search for one that is one size larger. Continue in that fashion, one step at a time, until the desired size is attained. The reason I prefer Mikuni is that jet sizing is tied to millimetres; a 25 slow jet is 0.25mm, so it's easy to make incremental steps without much fuss. A similar process with a Keihin jet requires a cross-reference chart to convert Mikuni (or millimetres) to Keihin.

Generally, Mikuni jets are sized by flow rate over hole size and Keihin are all based on hole size. However, not all Mikuni's are strictly flow rate based depending on the jet model. yadda yadda, etc. etc.

Just to keep it entertaining I guess.

In either case, the Hawk pilot is hole size based, so the 40 pilot is .40mm. In order to achieve a "45" pilot, a .45mm hole is needed.

In Micro drill gauge, this would be a 77 (.4547mm) Alternatively, you can buy metric micro bits and get them in .05mm steps .40 .45 .50 etc.

[NzBrakelathes]

Originally Posted by o2jmpr

Does anyone have a video they could share of how to drill out the pilot jet on the stock PZ30? I know a few of you have done it but I've never seen it done. They way people speak of it, it seems there must be some level of risk in ruining the jet/carb.

Or look in my eBay link below
Tune kit with jets etc and can add more
I’m in the USA till Monday so I can’t send till next week
My kit can have small increment sizes up from 105 main or pilot 40 and up

[kingofqueenz]

Have to forgive me for the foolish question.

Why risk drilling when you can buy jets? (well most of 'em at least ).

This is crazy talk I tell you

[Megadan]

Originally Posted by kingofqueenz

Have to forgive me for the foolish question.

Why risk drilling when you can buy jets? (well most of 'em at least ).

This is crazy talk I tell you

In this instance, I agree with you. If the jet is available, then buying a jet that is sized by the manufacturer is the best way to go.

Reasons for drilling? No available jets. Jet size you need to get an ideal tune doesn't exist - IE One size is a little too lean, next size up is a little too rich, you may be able to open the jet up to a hole size between those two. You often see that done on race bikes where they want to squeeze every last bit of power out of the motor for given climate conditions.

[OneLeggedRider]

I drilled my pilot to .45mm and it's a definite improvement, but I'm at 2 turns out on the mixture screw so I probably need a .48mm.

[kingofqueenz]

Fair points Dan ( as usual ).

As my TBR is my first bike ever, I'm forever learning the carb tune... it equal parts "art" and science.

Just when I think its perfect, I tweak for sh*ts and giggles and its even better.