Carb Questions

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GreyImport
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Carb Questions

Postby GreyImport » Sun Jul 21, 2013 1:00 am

Just pulling down the carbs and want to know why the pilot jets differ ... three are solid and the one on no.2 carb has holes in the side .

I realise that 2 & 3 are setup differently than 1 & 4 , so should there be 2 solids and 2 with holes?

Ive already found plenty of poor work from the previous carby overhauler so anything is possible.

The clip on the needle in 4 had fallen off so it was just free falling inside ..... just out of curiosity , what would this do to the performance?

Thanx


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1990 FZR250R 3LN1
1977 Triumph Bonneville 750 T140V
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GreyImport
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Re: Carb Questions

Postby GreyImport » Mon Jul 22, 2013 1:58 pm

Anyone ? :headscratch:
1990 FZR250R 3LN1
1977 Triumph Bonneville 750 T140V
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SouthendChris
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Re: Carb Questions

Postby SouthendChris » Mon Jul 22, 2013 4:17 pm

I could only assume that it has something to do with running the centre cylinders richer than the outer two. They run hotter so the extra fuel helps keep the cylinders and piston crown cooler. Why would the pilot jets need to be like this??? Maybe rolling off the throttle at high rpms???? :headscratch:

The 3LN parts book doesn't have different part numbers for these, suggesting they are/should be the same OR Yamaha sells them as a set of 4.......

Whats the size marking on yours??

Chris
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GreyImport
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Re: Carb Questions

Postby GreyImport » Mon Jul 22, 2013 9:06 pm

Hi Chris ....
That was my assumption too as the main jets and needles are in "pairs"

The only thing I could find is that they are called bleed and non bleed jets ..... :headscratch:

seems no one knows ..... screwy

http://www.thumpertalk.com/topic/243979 ... ifference/

http://www.gixxer.com/forums/showthread.php?t=223951

Jets with the holes are 10s

Solid ones are 30s

From the spare set of carbs theres 2 with holes, 1 is shredded inside and cant be removed from the jet housing and 1 is missing (the carbs were partly disassembled and came with a spares bike )

My only conclusion is the bike should have the non bleed type as they are #30s which is wat is stipulated in the parts cat.

Annoyingly I only have 3 of each type

banghead
1990 FZR250R 3LN1
1977 Triumph Bonneville 750 T140V
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GreyImport
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Re: Carb Questions

Postby GreyImport » Mon Jul 29, 2013 2:01 pm

So nobody knows why there are bleed and non bleed pilot jets?

Interesting stuff

:jawdrop:
1990 FZR250R 3LN1
1977 Triumph Bonneville 750 T140V
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http://2fiftycc.com/index.php
EMAIL: greyimport@2fiftycc.com

LiteTek Carburettor Seal Kits
http://www.litetek.co/index.html

DonTZ125
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Re: Carb Questions

Postby DonTZ125 » Mon Jul 29, 2013 3:43 pm

Yamaha in its wisdom changed the style and size of idle jet twice; the 3LN1 had the 4G0-14142-30 solid #30, the 3LN3/5 had the 1NT-14142-10 perforated #10, and the 3LN6/7 had perforated #12.5.

However you look at it, you should probably have a set of 4.

Also - when running stepped main jets, the center cyls use SMALLER jets. It's not about cooling the crowns, but rather matching the reduced air mass flow of the hotter center cyls.

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GreyImport
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Re: Carb Questions

Postby GreyImport » Mon Jul 29, 2013 11:59 pm

Thankyou :thumbsup:
1990 FZR250R 3LN1
1977 Triumph Bonneville 750 T140V
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http://2fiftycc.com/index.php
EMAIL: greyimport@2fiftycc.com

LiteTek Carburettor Seal Kits
http://www.litetek.co/index.html


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