Jetting for 1990 F2

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kjellz
Posts: 69
Joined: Mon Jul 03, 2017 7:01 am
Location: Norway

Jetting for 1990 F2

#1 Post by kjellz » Sat Jan 27, 2018 7:35 pm

Hi
I took apart my carbs and I found the following;

180 mains
27.5 pilot
4th clip counting from top down
Throttle valve nr 2.0
Needle 5k1
Conditions sea level, usually below 20 celsius.
All stock except Figaroli pipes.

The bike is Brazil made for Italian market and has carbs marked "2UA-00". According the manual I found the mains should be 250 as stock! This seems like a big gap, although the bike is running good in the upper half of the range. Plug electrode nice tan brown, but carbon deposits at plug face area. The idle-to-pull-away is poor, bogging strongly every time. But this should be pilot issue right?

Anyway, can anyone help vonfirm what is correct base setup for this carb/bike.

At least I plan to try pilot one notch up to 30, but uncertain if the 180 main is way to lean?
And is the clip pos correct? (Manual in Italian language left me with some unanswered questions).

Thanks
Kjell
Last edited by kjellz on Thu May 10, 2018 3:09 pm, edited 1 time in total.
----------------------------------
RD350 YPVS 1990
F2 converted to N2 Red/white 1986 - Figaroli pipes

hondaror
Posts: 2828
Joined: Mon Mar 03, 2014 8:44 pm
Location: Alberta, Canada

Re: Jetting for 1990 F2

#2 Post by hondaror » Mon Jan 29, 2018 2:26 am

Are the carbs the type with power jet? If so, I'd bet the jets in there are 65 l/s and 60 r/s. (It says in the manual what those are. Not to be removed.
The slide cut away will be your off idle jetting. You might want to pull those and compare the #s to stock.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine

justind97
Posts: 202
Joined: Mon Aug 10, 2015 8:57 pm
Location: Ottawa, Canada

Re: Jetting for 1990 F2

#3 Post by justind97 » Mon Jan 29, 2018 1:43 pm

I believe 185 is right for Power jet carbs. The power jet adds 60 points to equal 245. Yours is slightly leaner than stock.

31k carbs came with 240 stock.

27.5 pilot is correct.
clip should be 2nd from the top.

kjellz
Posts: 69
Joined: Mon Jul 03, 2017 7:01 am
Location: Norway

Re: Jetting for 1990 F2

#4 Post by kjellz » Mon Jan 29, 2018 2:52 pm

If I go by the frame number and look up the manual at rd250lc.net the following carb data is in the manual:

Here it reads 250 main as stock, which seems huge.
Mikuni 2UA-00.jpg
Mikuni 2UA-00.jpg (101.58 KiB) Viewed 2061 times

Furhter I cannot tell if this is a power jet type carb or not?
20180129_181856.jpg
20180129_181856.jpg (128.12 KiB) Viewed 2061 times
The slide has 2.0 stamped as shown (not 12 as I first thought it read. Edited.).
This is stock if my interpretation of the Italian manual is correct.
Mikuni 2ua slide.jpg
Mikuni 2ua slide.jpg (78.94 KiB) Viewed 2061 times
Last edited by kjellz on Thu May 10, 2018 3:10 pm, edited 1 time in total.
----------------------------------
RD350 YPVS 1990
F2 converted to N2 Red/white 1986 - Figaroli pipes

MK
Posts: 814
Joined: Sat Nov 26, 2005 11:44 am
Location: Wolfenbüttel, Germany
Contact:

Re: Jetting for 1990 F2

#5 Post by MK » Mon Jan 29, 2018 3:34 pm

That looks like the PJ carbs, but your jetting chart shows no PJ jet. That'd mean 180 is way too lean.
Check the tube on the right of your pic. Where it connects to the float bowl, there should be a brass jet inserted (looking from the float bowl). If there is one, 180 seems in the ballpark. If not get what your chart says (250).

The rest is a bit different from other models, but should do the job "as is".

The German 1UA's have a richer needle 5L20 instead of the older models 5K1.
The older 31K models have a P-2 needle jet whereas the F2 have a N-8 with just 2 bores (4 holes).
Bye
Martin

evan_calgary
Posts: 1368
Joined: Tue Nov 12, 2013 2:34 am

Re: Jetting for 1990 F2

#6 Post by evan_calgary » Mon Jan 29, 2018 11:42 pm

As for your question on when bits of the carb have the most impact, see here:

http://all-offroad.com/main/wp-content/ ... -chart.jpg" onclick="window.open(this.href);return false;

hondaror
Posts: 2828
Joined: Mon Mar 03, 2014 8:44 pm
Location: Alberta, Canada

Re: Jetting for 1990 F2

#7 Post by hondaror » Tue Jan 30, 2018 2:53 am

Yes it is power jet. The rubber hose on the right side of the carb in your pic. The left carb has the 65 pj and the right carb has the 60pj. The power jet works on roughly half throttle to full throttle and the 180 main jet is added to the pj size to give you the total main jet size. 180+65 for 245 on the left side, which runs slightly hotter than the 240 on the right side.

Now, the 2.0 on the underside of the slide refers to the slide cutaway. I believe the 2.0 stands for 2mm. You can measure the height of the cutaway from the base of the slide to confirm this. If that is not the case, you will have to reference the cutaway size and go with a larger cutaway to lean out your off idle mixture. Conversely, a smaller slide number, will give you a richer off idle mixture.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine

kjellz
Posts: 69
Joined: Mon Jul 03, 2017 7:01 am
Location: Norway

Re: Jetting for 1990 F2

#8 Post by kjellz » Tue Jan 30, 2018 8:04 am

Thanks. Lots of info to look into.
But one more thing; does this carb have a normal Mukuni model code/ equivalent or is it all oem for Yam? Related to getting parts and so on...
----------------------------------
RD350 YPVS 1990
F2 converted to N2 Red/white 1986 - Figaroli pipes

hondaror
Posts: 2828
Joined: Mon Mar 03, 2014 8:44 pm
Location: Alberta, Canada

Re: Jetting for 1990 F2

#9 Post by hondaror » Tue Jan 30, 2018 8:34 pm

I think all that stuff is still available from Yamaha, OEM.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine

kjellz
Posts: 69
Joined: Mon Jul 03, 2017 7:01 am
Location: Norway

Re: Jetting for 1990 F2

#10 Post by kjellz » Sat Apr 14, 2018 6:10 am

Update:
I found a way to check the power jets of the 2UA-00, for peace of mind and for reference to others with similar questions.
-I got hold of some loose 1N type jets of sizes 60 and 65 and used some small carburetor cleaner steel pins that would just fit through these jets. Then I tried to insert these carefully through corresponding bores of the power jets.
And yes the power jets seems to have similar or slightly larger bore diameter compared to these "loose" jets so the 185+60/65 seems to fit well.
I have no idea of the validity of such a test, but it seems to confirm what has been suggested above here with regards to Power jet carbs (2UA-00 at least).

I noticed others referring to this carburetor as Mikuni VM26 with power jets....

Kjell
----------------------------------
RD350 YPVS 1990
F2 converted to N2 Red/white 1986 - Figaroli pipes

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