Carb needles
- Thread starter bikerboy7
- Start date
I didn't know they were, but it seems you are right bikerboy.
I hope someone chirps in who knows more than us, it isn't just the top fixing is it because of the orientation.
No doubt we will be edumicated, again.
Upt'North.
I hope someone chirps in who knows more than us, it isn't just the top fixing is it because of the orientation.
No doubt we will be edumicated, again.
Upt'North.
bdalameda
PaleoCyclist
The parts list on Partzilla shows numbers 18 and 19 being the LH and Rh carbs needles but the part numbers are the same so they are identical. This is for a 1997 ABS II
I'd guess the needles are different to satisfy mounting and construction requirements of a left bank vs. a right bank of carbs. These would be mechanical differences. Both banks have to flow the same air volumes with the same fuel air mixtures at all speeds, so the tapers and size are probably identical, as are the jets.
That is interesting ...... good catch. I just looked at the part numbers at Partzilla and it looks like for the earlier year ST1100, the needles are different part numbers, but for the latter models they are the same ( ??? ). And for my '98 model, only the PN for the one side is listed, the PN for the other side is missing.
There must be a slight difference in taper between the two different part numbers. That would cause the mixture to be slightly different at any given slide opening. Maybe Honda did that on purpose, or maybe it was just a "mistake" that "slipped through a crack" , or maybe they did it on purpose to equalize the mixture between cylinders but then decided it didn't make that much of a difference and started installing the same PN later, to simplify things.
I bet if you changed the positions, you wouldn't be able to tell the difference, if there isn't much of a visible difference in taper between the two PN's.
There must be a slight difference in taper between the two different part numbers. That would cause the mixture to be slightly different at any given slide opening. Maybe Honda did that on purpose, or maybe it was just a "mistake" that "slipped through a crack" , or maybe they did it on purpose to equalize the mixture between cylinders but then decided it didn't make that much of a difference and started installing the same PN later, to simplify things.
I bet if you changed the positions, you wouldn't be able to tell the difference, if there isn't much of a visible difference in taper between the two PN's.
STraymond
Site Supporter
Yes, for a 2002 model.
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My needles are the same
2 x J1BP
2 x J1BQ
The Official part numbers for my bike (2000 ST1100AY - Police)
16131-MAJ-R00 (Front or Left Pair)
&
16191-MAJ-R00 (Rear or Right Pair)
Whats interesting though is that I interpreted the parts fiche as showing a front vs rear difference, now that I looked again I can see that it may be a left vs right difference.
I foolishly let my needles get mixed up when they went for cleaning, you mention #1/3 = J18P & 2/4 = J18Q , was this from observation i.e. when you pulled them from the carb bodies
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Yes the interpretation I think should be left side and right side not front and rear. My RHS needles have a differ part number to you though. Detials:
right hand side is (1 and 3) #16151-MAJ-r00 markings J18p,
left hand side (2 and 4) # 16131-MAJr00 markings J18Q, this is as far as I can remember hope this helps.
Update: think the carb needles are paired front and rear. The two thinner needles on the back, thicker on the front. Thinner needles would make for a richer mixture and so cool cylinders on the rear and front ones would be cooled by air flow more than rear ones. This I suppose would mean even cooling on all cylinders. Your opnions please!!
Was wondering if you ever got an official answer on this one ? My query to Honda Japan got lost in the post , I aim to pick it up again soon once the local dealer gets back to more normal functioning. Its now going to be a long while before I need to deal with this again but figured I should try and find out the official answer before I do !
With a liquid-cooled engine, cylinder position should make little difference in temperature-caused mixture need differences. You could also say that the front cylinders are nearer the radiator.
My guess is the position of the jets within the bodies of the carbs are the same within each carb, and thus different for each side of the bike, to compensate for acceleration-caused fuel slosh.
Nope I didnt still a bit puzzled.
I have rebuilt several Honda 4's...both inline and V configuration. All the needles were identical.
Recently rebuilt the carbs on my 1991 ST. The needles in the rebuild kits were identical. Post rebuild, the bike started right up and needed little adjustment to synch. Runs fine.
Note: IPB's for the 1991-1999 show two different part numbers two go into the left carbs, two go into the right carbs. I checked the IPB for the 2000+ST1100....all four have the same part numbers.