Carb id

[MNS494]

I'm tfrying to see if the carbs are stock on my 81 mns...on the top side of the carb, partially under the choke lever are these numbers

3h5 oo
b065

mean anything?

[CatatonicBug]

I'll check on mine when I get home. Are yours painted black? The bodies and bowls should be black, and the tops should all be gold. The '80 MNS had only the outer 2 (1 and 4) gold.

[bikerphil]

I'm tfrying to see if the carbs are stock on my 81 mns

Post a couple of pics, then someone should be able to ID them for you.

[Crazcnuk]

3H5 is the designation for 1980G (standard) models.

However, we have seen many wierd combos.

[CatatonicBug]

Mine have no such numbers in that location. All I have is a big "MIC", then, under that is "Mikuni", then under that is "Kogyo". No numbers at all. As Craz said, it looks like those carbs may be from another bike.

[Crazcnuk]

Those numbers can be very hard to see. They are very faint, etched, kind of. There are no indents or raised parts of the number, more like a silk-screen.

You have to get th light on them just right, sometimes, in order to see them.

[MNS494]

tTHE CRAZYCANUK IS RIGHT...I'VE FOUND OUT THEY'RE FROM AN 80 STANDARD...NOW I NEED TO FIND OUT HOW AN 80 STANDARD WAS JETTED.......HOPE THIS ISN'T THAT OLD 80'S --NEW 80'S THING........THANKS...I THINK I'M CLOSING IN ON A GOOD RUNNING BIKE......

[Crazcnuk]

The 80G carbs were originally set up as:

mainjet

115 Outside carbs
120 Inner carbs

X-2 needle jet

25 starter jet

42.5 Pilot jet

140 Air jet, main

185 Air Jet, pilot

Needle 51 Z7

Float height .906 +/-.20in


81 LH

110 Outside carbs
120 Inner carbs

X-2 needle jet

25 starter jet

42.5 Pilot jet

140 Air jet, main

185 Air Jet, pilot

Needle 5GL-16

Float Height .12 +/- .04in

The later service bulletins just say to use #110 mains on all 4 cylinders. So the only differences are the needle and the float height.

[MNS494]

Thank you , thank you, thank you.....i'll order the right needles this morning from my yamaha dealer and put it together when they get here........we put a wire guage on my pilot jets and they measured 55+.....so i've got 42.5's coming....don't know why those were in there.....thank you again craz...you've got one person thinking good thoughts about you...hope it brings you good luck...

[MNS494]

Nothing ever is easy....does anybody know, or tell me where to find, the yamaha part number for a jet needle 5 I Z 7 ?........ It would save me having to deal with the parts guy...

[bikerphil]

Those needles aren't easy to find and ain't cheap. IIRC, you gotta buy a whole carb kit which includes them. What needles do you have now and why are you changing them?

[MNS494]

I found out my carbs are from an 80 standard and someone jetted it thinking they were stock....an 81 mns.....so everything is the same except the jet needle and the mains and the float height....soo............i 'm putting the float height at 23mm.....i think i can get away with the 110 mains all the way across cause boise is 2900 ft. Up...............right now the needles are 5 g l-16 's and i'd be happy if you think i could get away with those....i'll probably never get over 80 mph........

[bikerphil]

There is no reason the ones you have won't work unless they are badly worn. Go with what you got. Make sure you run the rubber plugs over the pilot jet tunnels tho.