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post #1 of 7 (permalink) Old 04-11-2011, 07:42 PM Thread Starter
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Carb Jet Needle Size

I cleaned my carbs yesterday, and I'm surprised at what I found.
Both were pretty clean inside, and the rear carb had some gunk in the bowl.
Both main jets are 132's but the jet needles are different than the manual says they are supposedto be.
Front is supposed to be N27J and rear is N27K
Mine are N27H front, and N27M rear.
What is the size for? Is it the shaft diameter of the needle, or length?
I thought about adding 2 thin steel washers underneath them cause I am going to do an earshave on this old beast. And I know I need to rejet as well, just haven't figured what size I will need.
According to the manual the 700's were already set up for high altitudes.
I'm at roughly 3200 feet, and I will be in the upper 6 to 7000 foot range this summer. I'm trying to figure this out before I put the carbs back on the engine so I don't have to pull them again.

Last edited by RakerBill; 04-11-2011 at 07:43 PM. Reason: Adding content.
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post #2 of 7 (permalink) Old 04-11-2011, 08:44 PM
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Quote:
Originally Posted by RakerBill View Post
I cleaned my carbs yesterday, and I'm surprised at what I found.
Both were pretty clean inside, and the rear carb had some gunk in the bowl.
Both main jets are 132's
What is the size for? Is it the shaft diameter of the needle, or length?
I thought about adding 2 thin steel washers underneath them cause I am going to do an earshave on this old beast. And I know I need to rejet as well, just haven't figured what size I will need.
According to the manual the 700's were already set up for high altitudes.
I'm at roughly 3200 feet, and I will be in the upper 6 to 7000 foot range this summer. I'm trying to figure this out before I put the carbs back on the engine so I don't have to pull them again.
Wish Ron were still around.

Yes, size is determined by diameter of hole....132 are not as big (diameter) as 140. Another way to say it....132 is leaner than 140
As I understand it....
Higher altitude means less oxygen which means less fuel is needed. I live roughly at SL and Ron told me to go with 140 or 142 mains with the shave. So if you're higher, logic tells me a leaner jet is needed. So maybe the 132 jets you have are fine.
I hope someone can shed further light on this.

Last edited by VoIPDoc; 04-11-2011 at 08:57 PM.
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post #3 of 7 (permalink) Old 04-11-2011, 09:01 PM
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Quote:
Originally Posted by VoIP Doc View Post
Wish Ron were still around.

Yes, size is determined by diameter of hole....132 are not as big (diameter) as 140. Anoterh way to sat it....132 is leaner than 140
As I understand it....
Higher altitude means less oxygen which means less fuel is needed. I live roughly at SL and Ron told me to go with 140 or 142 mains with the shave. So if you're higher, logic tells me a leaner jet is needed. So maybe the 132 jet you have are fine.
I hope someone can shed further light on this.
An accepted rule of thumb is above 1500 feet 1 size smaller on the main jet up to 2000 feet. Then it is 1 size smaller for every 2000 feet in height.
Jim
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post #4 of 7 (permalink) Old 04-11-2011, 09:04 PM
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We need to build a chart for this stuff. If everyone who has done an ear shave would chime in on what they're running, we could build the chart.

I'm also near sea level and I got 142 jets from Clock152 here.
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post #5 of 7 (permalink) Old 04-11-2011, 10:12 PM
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Quote:
Originally Posted by VoIP Doc View Post
Wish Ron were still around.

Yes, size is determined by diameter of hole....132 are not as big (diameter) as 140. Another way to say it....132 is leaner than 140
As I understand it....
Higher altitude means less oxygen which means less fuel is needed. I live roughly at SL and Ron told me to go with 140 or 142 mains with the shave. So if you're higher, logic tells me a leaner jet is needed. So maybe the 132 jets you have are fine.
I hope someone can shed further light on this.
I live bout 600ft above sea level and I ran a 148 and a 150 with no shims,that sounds a little big to most folks but it worked fine for me,but if you are running at altitude most of the time,I would go back to what came stock on most 750's after the ear shave ,try around a 138 and a 140 to compensate for the additional air the ear shave provides.Also,you can change the main jets without removing the carbs,but it's tuff.

Sounds like your bike was either rejetted for higher altitudes before you got it or in may have had California emissions controls on it from the factory,I don't know if they were jetted differently or not,but that is another possibilty




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post #6 of 7 (permalink) Old 04-12-2011, 01:51 AM
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Here some info I just posted on asbrands earshave thread:


I started compiling some jetting info when Ron passed.
Here is what I gleaned from one of Ron`s posts for the jetting on his 700, "Ol Yella".
I am hoping your elevation is close to Ron`s.


Quote:
Elevation 1,000 feet ASL (above sea level)
#40 Pilot Jet
#142 Main Jet, with 2 shims per needle
Idle/air (?)... I think this is a typo and really means fuel/air mixture screw) @ 2.75 turns with earshave using K&N pod filters

Has V&H cruisers with the baffles and reed valve coasters (and runs like a bat out of hell).

Most use #140 Main Jets with stock exhaust.
Lower elevation (denser air)- use bigger jets (larger number) for more fuel.
Higher elevation use smaller jets for less fuel.

Ron/lance kept his #145 Main Jets to use if he decided to remove his exhaust baffles.

Here is a link to Jets R Us, but someone else will have to help you pick the right ones.
http://jetsrus.com/index.html

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post #7 of 7 (permalink) Old 04-19-2011, 02:57 AM Thread Starter
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N27H front, and N27M rear jet needles are the correct size for this bike. It is not a California emmisions bike. I have added 2 thin steel washers under the needles, and I am going to stay with the stock jets for now, and see how she runs. If it's running too fat, I will pull the shims. I'm at roughly 3200 feet asl, and will going as hi as 5500 feet this summer.
I bought a screwdriver with a 90 degree ratcheting head to pull the bowl screws if I need to re-jet. Will make it easier to get them off w/o a carb pull. And I think if I'm not mistaken, Holley carb jets should work on these Keihin carbs. I'm going to check on this tomorrow.
One other thing, can I run with just the pull cable on the carbs? The return cable is rusty, and VERY stiff to move in the jacket. The pull cable is fine. Would it be a safety concern till I get a new set of cables?
As always suggestions and ideas are welcome.
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