What's the story about holes in pilot jets vs. no hole?

[Nessism]

Need a couple of 17.5 BS Mikuni pilot jets due to stripping issues. The OEM pilots don't have holes but most I find do, including those on Z1.

What's the deal? I found a couple w/o holes on ebay I'm most likely going to order but I am interesting in learning the differences.

[Fjbj40]

Air bleed holes to help with atomization, destroy the surface tension to help fuel atomize more readily.

Maybe some carbs have an air source that feeds the pilot orifice while other carbs do not. So if a carb has no air source going to that pilot orifice then it should make no difference what pilot you use. If it does have air in that orifice then pilot selection would be critical.

This is just an educated guess on my behalf, only thing that makes sense though. I have noticed this also in different carbs I have rebuilt, just never questioned why myself.

Good question though!

[Nessism]

Found this little tidbit describing the difference between the VM and BS pilot jets.

No explanation as to why some BS pilot jets have the holes and others don't. Guess we just need to use what Suzuki intended and don't question.

[nastyjones]

Need a couple of 17.5 BS Mikuni pilot jets due to stripping issues. The OEM pilots don't have holes but most I find do, including those on Z1.

What's the deal? I found a couple w/o holes on ebay I'm most likely going to order but I am interesting in learning the differences.

I chased an issue with the carbs on my 1100 for a year. The bike would only run on 3 cylinders until a couple of thousand rpms then #4 would kick in. Finally found out one of the pilots was the no hole kind. Replaced it and the bike runs fine now, so it is critical to use the correct pilots.

[TxGSrider]

I can tell you that if you use the ones with 6 holes in a carb that's not designed for them, it'll be stupid rich... and it'll drive you nuts trying to figure out what you screwed up. lol

[Steve]

OK, so the question seems to remain, is there a pattern to which carbs need the bleed holes and which carbs don't?

Since I have been known to rebuild a set of carbs every now and then, that is something that would be important for me to notice. For example, nastyjones had one carb that was different from the others. Rather easy to assume which one was 'wrong', but what if that one was actually right, and THREE of them were wrong?

I will be following this thread to see what develops.

.

[TxGSrider]

OK, so the question seems to remain, is there a pattern to which carbs need the bleed holes and which carbs don't?

Since I have been known to rebuild a set of carbs every now and then, that is something that would be important for me to notice. For example, nastyjones had one carb that was different from the others. Rather easy to assume which one was 'wrong', but what if that one was actually right, and THREE of them were wrong?

I will be following this thread to see what develops.

.

I suspect that the ones with the holes ("bleed style") will have a passage that connects from the pilot jet to the main jet.

[Nessism]

As far as I know all BS Mikuni's feed the pilot from the main. That's why there is a plug over the end of the pilot tower inside the carb.

Research shows the non bleed type are referenced by part number N151.067