Mismatched needles?

[AndyBCcoast]

Hi, I am going through my carbs and giving them a thorough clean, after a PO left the bike sitting for a couple of years with gas in the bowls and the tank. 

The damage was pretty minimal, but the carbs bowls were filled with a golden, sticky, crud that dissolves easily in Acetone.  I know these carbs have been cleaned before, because I found some mechanic's number marks scratched into the outside of the bowls. 

I have cleaned everything up, but was surprised to find the needle sizes were not the same, three of my needles were marked FZ74 and one marked FZ62. 

I had a set of spare carbs, so I decided to open up and see what it had for needles.  Again I found the same thing, three FZ74 needles and one FZ62....  Is this correct?  I have never had a bike with mismatched needles and suspect that maybe a FZ74 needle was damaged and needed to be replaced, in both carb sets. Perhaps the only available needle was an FZ62.....

Can anyone enlighten me!

Many thanks

Andy

[AndyBCcoast]

Hi, I am going through my carbs and giving them a thorough clean, after a PO left the bike sitting for a couple of years with gas in the bowls and the tank. 

The damage was pretty minimal, but the carbs bowls were filled with a golden, sticky, crud that dissolves easily in Acetone.  I know these carbs have been cleaned before, because I found some mechanic's number marks scratched into the outside of the bowls. 

I have cleaned everything up, but was surprised to find the needle sizes were not the same, three of my needles were marked FZ74 and one marked FZ62. 

I had a set of spare carbs, so I decided to open up and see what it had for needles.  Again I found the same thing, three FZ74 needles and one FZ62....  Is this correct?  I have never had a bike with mismatched needles and suspect that maybe a FZ74 needle was damaged and needed to be replaced, in both carb sets. Perhaps the only available needle was an FZ62.....

Can anyone enlighten me!

Many thanks

Andy

I should have added that the bike is a 1984 FJ1100.

Many thanks

Andy

[aviationfred]

My FJ's all have aftermarket needles. I can say for certain, different manufacturers have different shaped needles.

The needle on the left is a Hank Scott Racing brand. Notice how sharp the point is and the taper is pretty steep.

The needle on the right is a Dynojet Brand. A much more blunt tip and a very gradual taper.



Fred

[Dads_FJ]

All four needles should be the same, and good catch on noticing the odd duck.  The only exception I can think of with different jets between cylinders is some people richen the middle two to keep them cooler, and I believe this is done by either turning the mixture screws and/or a size larger pilot jet.  Father Pat can weigh in on that discussion, but that's a different topic and not what you have going on here...

[AndyBCcoast]

Thank you both for your comments.  I was a bit foxed when I found two sets of carbs with mismatched needles.  I think I will replace the FZ62 needle with a FZ74 and then see how the carbs perform.

I spent most of yesterday working on the carbs and now have them clean enough to put back on the bike.  Although the bike turns over when I jump it with a battery I have no idea if the bike will run, I bought both FJ's as non-runners.  I pulled the valve cover off a few days ago; everything was spotless, the cams look brand new and have no wear marks.  I suspect the bike does have a fairly low mileage, although the 11,000 km on the speedo is suspiciously low!  Just giving everything a scrub and clean, looks like new brake pads all round and new braided brake hoses in the front.  I will rig up a jockey fuel tank this weekend, install new plugs, and see if she will start.

Appreciate the help.

All the best

Andy

[fj1289]

My FJ's all have aftermarket needles. I can say for certain, different manufacturers have different shaped needles.

The needle on the left is a Hank Scott Racing brand. Notice how sharp the point is and the taper is pretty steep.

The needle on the right is a Dynojet Brand. A much more blunt tip and a very gradual taper.



Fred

And to add to what Fred has here - your needle selection can have a BIG effect on main jet selection.  

Several years ago I installed a factory pro jet kit at 4500' elevation.  I called for jetting recommendations and Marc (the owner) answered.  After getting his recommended jetting for altitude I asked about the much larger main keys he recommended vs what I had previously used.  He explained the needle size and shape influences the flow through the mains even at wide open throttle.  So even though you only "tune" the main jet for WOT - the needle you are running will determine the "range" of the main jet.  

I hadn't realized this since my previous stock carbs had a dyno jet kit in them when I got the bike (and dyno jet uses a different main jet design/numbering system).  But this set of carbs I had already jetted with stock needles and Mikuni main jets - then swapped to the factory pro setup that also uses Mikuni main jets and was shocked to see a jump in main jet size by about 25 if I remember correctly (from 110? mains at that altitude to 135? I think).