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Location:
Melbourne
Registered:
May 2002
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Size of 18rg carbs
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Sun, 05 October 2003 01:05
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I have heard so much bullsh*t about these bloody things that I cannot figure out weather the 18rg carbs are the same as the 2tg carbs. I realuse that the jetting will be different, but I want to know if the 18rg jobs are 44mm as many would have me believe. I have never had them off an engine to check, so I can only guess.
Can anyone tell me where to get jets for 2tg Mikuni's to suit a 1940cc 2TG, I know the jets are easily obtained in the states, but does anyone here have a comprehensive set of jets for sale?
Cheers
Malkom
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Location:
Adelaide
Registered:
June 2003
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Re: Size of 18rg carbs
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Sun, 05 October 2003 02:17
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Both the 18rg and 2tg carbies measure 40mm at the butterfly valve.
Some have removable parts that can give the impression that they are 45ish mm (at the entrance).
The reall issue is the size of the large venturi.
These tend to be either 32mm (old types) or 31mm (new types)
These are the parts that actually govern how much air is allowed to flow through the carburettor. (they should not be removed, their purpose is to build up the vacuum within the carburettor to a certain level so that the correct amount of fuel will be drawn through. If you wanted to change these for larger items (possible with Dellortos) thenh you'll need to re jet them as well.
I hope this answered you questions
Your best bet for jetting this type of thing is to try people who do dyno tuning, they might have an array.
For an engine like that, I would think a set of 18rg carbs should be ok (18rg is 1968cc) as the capacity is quite similar and the two engines shoudl behave similarly.
Do a search for an attachment called Jetting.exe I can not remember who made this little program, but it shoudl help you out.
http://members.aol.com/dvandrews/
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Location:
nth ringwood, Victoria
Registered:
August 2002
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Re: Size of 18rg carbs
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Sun, 05 October 2003 08:25
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actully 2tg had 30mm chokes in 1st engine then went to 32mm then with yamaha head version they had 34mm chokes ,the 18rg had 34mm chokes as std with a 145main jet and 170 air corrector and as the other guy said they were 40mm butterflys
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Club Member
Location:
sydney
Registered:
May 2002
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Re: Size of 18rg carbs
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Sun, 05 October 2003 21:25
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and the earlier carbs had sleves that you could take out to increase from 44mm to 48mm, i used to have pics somewhere?
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Club President
I supported Toymods
Location:
Sydney
Registered:
May 2002
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Re: Size of 18rg carbs
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Mon, 06 October 2003 10:00
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I don't have a set of 18R-G carbs here BUT read the factory manual and if VER clearly states that the factory 18R-G carbs were 44 PPH. Cam has my 18R-G manual or I would scan it for you !
IRA11Y also has a copy of the carby section so should be able to confirm that for you.
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Location:
Adelaide
Registered:
June 2003
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Re: Size of 18rg carbs
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Mon, 06 October 2003 13:42
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That is interesting about the large venturis.
We've got two sets of 18rg carbies, the really old ones have 32mm ones and the new ones have 31mm ones.
The 2tg (88220/222 (difficult to read)) carbies we've got have 32mm venturis.
We've got the 1977 version of the 18rg engine manual and it says the the carburettas are called "40-phh-4".
The old 18rg set we have are off an 88211 generation 18rg and came with 145 main jets and 200 air correctors.
The newer set of carbies we've got (88251) have 31mm venturis with 140 main jets and 145 air correctors. (note that these air correctors have been modified somewhere along the line, they have bigger holes that the 200's)
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Location:
Fl
Registered:
February 2003
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Re: Size of 18rg carbs
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Mon, 06 October 2003 16:12
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My 2tg has 9.8 pistons cams and p/p head with headers 44mm mikunis with No large venturi and jets are bigger to match the lack of large venturis. Runs well around town and on the top milage sucks though.
Greg
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Club Member
Location:
sydney
Registered:
May 2002
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Re: Size of 18rg carbs
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Mon, 06 October 2003 21:05
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I can also confirm the 32mm older venturi and 31 mm newer, ive got a big container of bits and pieces from the two sets ive pulled apart so if you need any measurements let me know.
unfortunately my copy of the manual is at my cousins place as he is setting up the twin solexs on his L20 180B
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