1UA carb confusion!

[Daren_Calgary]

Hey everyone,

I've got two sets of 1UA carbs. One set came off my '87, another from my '90. The set off of my 87 has a removable power jet, whereas the '90 has a press-fit non-replaceable power jet.
The stamps in each float bowl are different as well.

The '87 float bowl stamp reads as; P1-2. The removable power jet is a 20 and looks identical to the pilot jet.
The '90 float bowl stamp reads as; R1-1

From reading up on the 1UA carbs, the power jet on the press in style is 60 and 65 respectively. Should I just go on the hunt for pilot jets of the same size to screw in? I would use the float bowl from the '90, however, one of them is non-repairable.

Just curious if anyone has insight on this, and why one is removable. Or, is it a matter of incorrect float bowls?

Pictures below.

39F71F8F-910B-45F2-8304-907BA4A6CA9B[/img] '90 RZ Float bowl
7EA64EB7-C407-41E8-8115-B03BDB90BE05[/img] '87 RZ Float bowl

[MK]

Can't tell whether Yamaha changed the PJ from pressed to screws. Usually I'd say it's a modification from a previous owner.

Nevertheless #20/25 were the PJs for the 27 hp version. The unrestricted had #60/65.

[Daren_Calgary]

After searching for a while, it seems that the R models came equipped with a removable power jet 20/25. If I can source some 60/65 pilot jets would these act the same as the unrestricted carbs?

[MK]

I guess the right jet should be N100606
https://www.mikuni-topham.de/DEUTSCHSIT ... e61-62.pdf

Can't tell for the R models, but the restricted German models also had a smaller main air jet (0.7 instead of 0.8).
It's the bore size behind the brass ball in the carb intake. To modify it, you need to remove the ball.

[Daren_Calgary]

The N100606 would not fit. The jets that came out of the carb are the M28/1001 style. Both are size 20. This is in line with the 1XE carb specs on the '86 N2.

[MK]

If you manage to get them in the right size, everything is fine.

Otherwise try the V17/1002 as you'll get them in #60/65.