Collecting too many Premier #17 Pilots Fix

kommando · Mar 27, 2021

Premier carbs run a bit lean on the pilot circuit and even though Amal supply the 850 specified Premiers with 19's there are others that they ship with 17's that then end up being swopped out for 19's. I had such a pair of 17's so decided to convert them to 19's. 19 thou is 0.48mm so I first tried a HSS 0.5mm drill but that snapped before any cut. The premier jet is steel not brass, so it needed a different approach so I went around to the mill and looked out a 0.5mm carbide end mill and used that on the lathe, it measured 0.48mm as did the HSS drill so the jet should only be slightly oversized. There was no feedback to the feed handle when feeding in, so took it very slowly, rpm was 80.

Collecting too many Premier #17 Pilots Fix

Mark Savage · Mar 27, 2021

If you want to swap a couple of 17s for 19s let me know. BNIB.

seattle##gs · Mar 27, 2021

I have at least six #17 collecting dust

Fast Eddie · Mar 27, 2021

Dommie Nator said:
If you want to swap a couple of 17s for 19s let me know. BNIB.View attachment 78827

Cab do you need some #17s ?

acadian · Mar 27, 2021

nice, FYI, for small work like that you should think about picking up a collet block

Mark Savage · Mar 28, 2021

Fast Eddie said:
Cab do you need some #17s ?

Yes, swap for a pair of 19s?

Matchless · Mar 28, 2021

acadian said:
nice, FYI, for small work like that you should think about picking up a colle

kommando said:
Premier carbs run a bit lean on the pilot circuit and even though Amal supply the 850 specified Premiers with 19's there are others that they ship with 17's that then end up being swopped out for 19's. I had such a pair of 17's so decided to convert them to 19's. 19 thou is 0.48mm so I first tried a HSS 0.5mm drill but that snapped before any cut. The premier jet is steel not brass, so it needed a different approach so I went around to the mill and looked out a 0.5mm carbide end mill and used that on the lathe, it measured 0.48mm as did the HSS drill so the jet should only be slightly oversized. There was no feedback to the feed handle when feeding in, so took it very slowly, rpm was 80.

I'm not surprised you snapped the drill if you're running at 80 rpm. I'm just amazed you didn't break the 0.5mm carbide end mill also. Spindle speed for .5mm HSS end mill would be around 5000 rpm on stainless steel & higher if using carbide.

Fast Eddie · Mar 28, 2021

Dommie Nator said:
Yes, swap for a pair of 19s?

PM’d yer.

cash · Mar 28, 2021

I've always done pilot jets by hand. Small drills are too easily broken by a machine.

kommando · Mar 28, 2021

cash said:
I've always done pilot jets by hand. Small drills are too easily broken by a machine.

The HSS drill or a drill that claimed to be HSS broke while I was drilling by hand using a knurled holder, the steel jet is a lot tougher than the normal brass. Never had a problem with hand drilling brass jets, just this steel premier pilot and did not want a broken drill stuck in the jet so went carbide instead.

cliffa · Mar 28, 2021

Had I realized they were steel ( which is an incredibly poor choice given then ethanol loaded fuel is hygroscopic ) I would not have chanced this...

I made a 19 drill holder / jet cleaner and ran it through my in situ 17's. It worked ok thankfully.

cash · Mar 29, 2021

Well I never, steel pilot jets. If I ever come across them, and no doubt I will I'll take care. I'm confident in my own ability to do the job.

Collecting too many Premier #17 Pilots Fix

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