Jet needle removal

[Bremer]

Hi, I am trying to get the jet needles out of my TR3A's carbs for inspection. I removed the screw in the piston, but can't pull the needle out. I tried penetrating oil without success so far. Any other tricks you could share?
Thanks!

 

[Moseso]

The part that needs inspection is already exposed. Shiny wear spots, down near the piston end will indicate contact with the jet -- in which case, both needle and jet should be replaced.

The only way I know to get the needle out of the piston, other than what you've already done, renders the needle suspect, at best. Clamp the needle in a vise and gently rotate/pull the piston off of it. VERY likely to scar or bend the needle.

It's really not that expensive a part. I say, when in doubt, replace 'em.

 

[Bremer]

Inspection was probably not the correct term, more identification. I am having fuel mixture issues and I'm trying to identify which needles are installed in my carbs. I am assuming that the ID is stamped on the part of the needle that is hidden from view.

 

[Moseso]

Yes, the needle ID is stamped on the shank of the needle, up in there where you can't see it unless removed.

I suggest more penetrating oil & time. Esteemed forumite, DrEntropy, promotes a 50 - 50 mixture of acetone and automatic transmission fluid, "Weasel P*ss," as the best penetrant anywhere. It's cheap enough to give it a try.

It's likely that no treatment is going to render your needles removable with fingers only, however. Line a vise with soft copper, gently clamp the needle and, being careful to apply no side pressure (don't bend the needle), twist and pull the piston up off the needle. I've done it. It works.

Make sure the needle slides into the piston easily when replacing. I used the old needle, chucked in a drill, and spun it in the hole with a drop of oil. That cleaned out whatever muck was in there. Blow out the hole with some compressed air and put a tiny dab of grease on the end of the needle, when installing, to minimize the possibility of having to do this again -- next time.

 

[Bremer]

Thanks Moses. I got them out exactly the way you described, and they appear to be undamaged. I have already reassembled everything and centered the jets. They are both "SM" needles, which seem to be the standard ones. Another potential root cause for my fuel mixture issues eliminated...

 

[vivdownunder]

If the problem persists, check with a magnifying glass if the jets are worn to oval.

If so, it's best to replace the jets and needles together as I did recently, with a noticeable improvement in engine tune. It also cured a bit of run-on that had crept in.

Viv.

 

[tomgt6]

Another item that causes trouble is if the throttle shaft (butterfly) openings are leaking air. I had a hard time tuning my carbs until I found that one of them was leaking air at the shaft.

Spray some carb cleaner on the shafts at the openings and see if the engine tone changes.

 

[Bremer]

Tried that Tom. No change. I rebuilt the carbs with oversize throttle shafts last year. There was very little air visible behind the throttle plates when fully closed (both carbs equally). I can't sync them at idle, the rear carb always draws more air, and idle speed is too high. Looking for an air leak and can't find it.