R80RT CARB

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phibbieman
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R80RT CARB

Postby phibbieman » Sat Aug 19, 2017 9:52 pm

Noticed that my mpg was getting worse recently and looking through the forum i found that maybe my needle jets were worn so i decided to get new needles and needle jets, my carbs occasionally leak nothing bad but i could never cure it.once i had the carbs off i looked a bit deeper and found that the floats were not equally level ,only one float was at the correct level,the other was at least 4mm higher,when the carb was on the bike i was only looking at the one float and adjusted the tang as necessary. Also noted that the corner of the not so old float bowl gasket was stopping the float from shutting the needle valve and therefore flooding, if you tap the side of the float bowl the float would move slightly sideways and clear the gasket.You can only see this when carb is off and you turn the carb slowly.I took the gasket off and cut a small bit off the corner.This gasket is 2 years old and has swelled over the years.
needles were well worn by the needle jets as seen from the marks on the needles

Carbs rebuilt and no leaks and waiting on decent weather to do carb trials

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phibbieman
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Re: R80RT CARB

Postby phibbieman » Sun Aug 20, 2017 7:32 am

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windmill john
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Re: R80RT CARB

Postby windmill john » Sun Aug 20, 2017 8:23 am

Is that an optical illusion, the needles look different lengths!
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phibbieman
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Posts: 28
Joined: Mon Aug 04, 2014 8:45 am
Country of Residence: scotland tayport
Location: tayport

Re: R80RT CARB

Postby phibbieman » Sun Aug 20, 2017 12:39 pm

Old needles measure 53 mm long.i did not notice the length of the new ones,If they are longer ,would it make it run weaker?.The new ones came from motobins

barryh
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Re: R80RT CARB

Postby barryh » Sun Aug 20, 2017 6:17 pm

If the new one is shorter as it appears then it would logically make the mixture richer not weaker.

What really counts though is the positioning of the start of the tapered section as that affects the point when it lifts out of the needle jet. You might be able to make a comparison by measurement from the base of the piston with each needle inserted in turn. The needles don't have a complex form they have a straight section 2.45mm in dia followed by a simple truncated cone reducing to 1.2mm at the tip.


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