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Re: Slide Cutaway at altitude [Re: desco] #558797
08/18/14 6:20 am
08/18/14 6:20 am
Joined: Oct 2012
Posts: 4,018
Running from demons in WNY
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Originally Posted by desco
John,
Where does one obtain these precision measuring devices so often referred to on this site


I'm a hillbilly...#36 drill bit is .1065 and maybe two bucks. Cheap drills may vary a bit in size...so use your micrometer on the shank end...to get rid of the 1/2 thousand, pointy end first in a drill,polish with #220 abrasive,measure with your micrometer.


I ride dinosaurs that eat money
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Re: Slide Cutaway at altitude [Re: aviator79] #558811
08/18/14 8:38 am
08/18/14 8:38 am
Joined: Mar 2005
Posts: 10,221
Boston, Massachusetts
J
John Healy Offline

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John Healy  Offline

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J

Joined: Mar 2005
Posts: 10,221
Boston, Massachusetts
I'm one of those Yankees who still has the dollar my father gave me in 1966 when I opened my first store. I will drive a car until the doors fall off and my family takes it away from me. My wife is embarrassed to give my old shirts to the homeless. But I would skip lunch for a week to have a set of accurate plug gages to measure needle jets, etc.

Even here at "John's Pretty Good Motorcycle Shop" we try to have the right tools to do the job.

In reality you need two for each size: a plus and a minus. This gives you a go-no-go pair.

Besides Hillbilly he needs a .105", not a .106".


Re: Slide Cutaway at altitude [Re: aviator79] #558819
08/18/14 9:18 am
08/18/14 9:18 am
Joined: Aug 2001
Posts: 2,640
Springfield Nebraska
Richrd Offline
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I once had to check 5 new 106 jets to get a pair that were the right size.


Rich (member ThreeMustGetBeers)
"It's not always about going fast. Sometimes it's nice to slow down" (Wendy E.2016)

69 bonney
72 commando
75 commando interstate
06 Suzu..Suzu.. uh appliance
couple of beesas a ducati
and the Snake Bike
and a Honda?
Re: Slide Cutaway at altitude [Re: aviator79] #558822
08/18/14 10:05 am
08/18/14 10:05 am
Joined: Jul 2014
Posts: 395
UK
C
craig Offline
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Posts: 395
UK
or forget the gauges and just measure the flow rate for each jet to get a matched pair , i use parafin and a stop watch , sounds crude but i find it works

Re: Slide Cutaway at altitude [Re: John Healy] #558830
08/18/14 11:20 am
08/18/14 11:20 am
Joined: Oct 2012
Posts: 4,018
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Originally Posted by John Healy
I'm one of those Yankees who still has the dollar my father gave me in 1966 when I opened my first store. I will drive a car until the doors fall off and my family takes it away from me. My wife is embarrassed to give my old shirts to the homeless. But I would skip lunch for a week to have a set of accurate plug gages to measure needle jets, etc.

Even here at "John's Pretty Good Motorcycle Shop" we try to have the right tools to do the job.

In reality you need two for each size: a plus and a minus. This gives you a go-no-go pair.

Besides Hillbilly he needs a .105", not a .106".


I got $20 that says you can accurately gauge a jet using a hand "sized" drill bit grin

The right tools? Sometimes the right tool is any tool that'll do the job without pain..
My LSR Triumph ran 124.9 and a 125.00 mph on the second run on a warm humid day.I do believe this is the fastest official speed of a naked stock swingarm frame 650 Triumph in recent history in a standing start competition. I'm a retired construction electrician not a pro mechanic.. The piston valve clearance reliefs were done my me with a hand held Dremel tool,The valve lash has never seen a feeler gauge,the timing is adjusted by without a strobe light. But it has been on a dyno several times to tune for the best power....
All the tools have little use if the person using them has no "feel" for the job at hand.
But...I took your advice and just bought a .106 go and no go gauges,7 bucks for both... :bigt


I ride dinosaurs that eat money
Re: Slide Cutaway at altitude [Re: Hillbilly bike] #558831
08/18/14 11:37 am
08/18/14 11:37 am
Joined: Jul 2014
Posts: 395
UK
C
craig Offline
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craig  Offline
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C

Joined: Jul 2014
Posts: 395
UK
sounds good to me , what fuel did you run ?[Linked Image]

Last edited by craig; 08/18/14 11:51 am.
Re: Slide Cutaway at altitude [Re: Hillbilly bike] #558833
08/18/14 11:52 am
08/18/14 11:52 am
Joined: Nov 2011
Posts: 4,737
U.S.
Magnetoman Offline

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Originally Posted by Hillbilly bike
I got $20 that says you can accurately gauge a jet using a hand "sized" drill bit
I've got $20 that says that while some people can, many people can not. Wear of only 0.0005" of the needle jet is enough to seriously upset the mixture, so what is required is a calibration standard -- either purchased or home made -- that is accurate to no worse than 0.0002". Making a measurement to an absolute accuracy of a few tenths with a micrometer is by no means trivial. Even if someone has a digital micrometer that has a resolution of tenths, that does not mean it is accurate to tenths. And, even if a micrometer is calibrated to an absolute standard by one person, that does not mean when the spindle is cranked down by a different they will get the same result to within tenths. Commercial plug gages eliminate all that.

Re: Slide Cutaway at altitude [Re: aviator79] #558850
08/18/14 1:26 pm
08/18/14 1:26 pm
Joined: Mar 2005
Posts: 10,221
Boston, Massachusetts
J
John Healy Offline

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John Healy  Offline

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J

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Posts: 10,221
Boston, Massachusetts
Quote
My LSR Triumph ran 124.9 and a 125.00 mph


As we are only interested in under 1/3rd throttle what you do on the main jet, while impressive, has nothing to do with the conversation. wink

This thread started with a problem at low throttle openings. As the needle jet is one of the underlying foundations of fuel delivery at these throttle openings we must keep the discussion on the parts of the carburetor that are in play. The needle jet is a main player and the only part in the carburetor subject to wear.

Have you had your micrometer checked for accuracy in the past 30 days? Did you have it done professionally with a standard that can be traced back to the Bureau of Standards? The people at Vermont Gauge do. Do you make sure the part to be measured is the same temperature as the instrument you are using. When you are measuring to tenths this matters.


Re: Slide Cutaway at altitude [Re: John Healy] #558870
08/18/14 2:22 pm
08/18/14 2:22 pm
Joined: Nov 2011
Posts: 4,737
U.S.
Magnetoman Offline

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Originally Posted by John Healy
Have you had your micrometer checked for accuracy in the past 30 days? Did you have it done professionally with a standard that can be traced back to the Bureau of Standards?
It's even more difficult than that. Even if your micrometer reads 0.0000" when the anvils are in contact and 1.0000" with a 1" calibration standard, that doesn't mean it will read, say, 0.1050" accurately. The 0" and 1" tests confirm the frame hasn't been sprung open or closed, which is a good test to do but it isn't sufficient.

Even if a micrometer were perfect when new, if it spent time in a production environment measuring parts of a specific size (i.e. with a specific angle of rotation of the spindle) there could be uneven wear of the threads. This isn't a hypothetical problem. My "Brown & Sharpe Micrometer Calibration Standards Set" contains 12 pieces (including, coincidentally, a 0.1050" gage block) to check the calibration with the spindle at 0, 90, 180, and 270 degrees.

As John wrote, for this application tenths matter. When dealing with needles and needle jets one needs to make measurements to an absolute accuracy of tenths, and having a micrometer with this resolution isn't nearly sufficient. Even with an accurate set of gage blocks and a good quality micrometer, making measurements that truly are accurate to tenths is by no means trivial.

Re: Slide Cutaway at altitude [Re: Magnetoman] #558910
08/18/14 6:40 pm
08/18/14 6:40 pm
Joined: Oct 2012
Posts: 4,018
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Originally Posted by Magnetoman
Originally Posted by Hillbilly bike
I got $20 that says you can accurately gauge a jet using a hand "sized" drill bit
I've got $20 that says that while some people can, many people can not. Wear of only 0.0005" of the needle jet is enough to seriously upset the mixture.


I was making reference to JH... wink Maybe .0005 wear on the jet needle is not such a bad thing with the usual E10 gasoline causing a slight lean condition on some engines. Non ethanol gas is sold around here and it does fuel better in marginal situations.


I ride dinosaurs that eat money
Re: Slide Cutaway at altitude [Re: aviator79] #558919
08/18/14 7:20 pm
08/18/14 7:20 pm
Joined: Mar 2005
Posts: 10,221
Boston, Massachusetts
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John Healy Offline

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Boston, Massachusetts
HB, if anything these AMAL's are already rich these days with what was stock jetting.

They run even richer if the slide clearance is reduced when the carb is sleeved. Most people who sleeve these carbs have learned this and use the standard .004" + slide clearance. This is the clearance the stock jetting is based upon!!


Re: Slide Cutaway at altitude [Re: John Healy] #558923
08/18/14 7:53 pm
08/18/14 7:53 pm
Joined: Oct 2012
Posts: 4,018
Running from demons in WNY
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Originally Posted by John Healy
HB, if anything these AMAL's are already rich these days with what was stock jetting.



What is reason? E10 fuel has a slightly lower stoichiometric point than non ethanol gasoline so it's going to be a tad leaner if all else is the equal.


I ride dinosaurs that eat money
Re: Slide Cutaway at altitude [Re: Hillbilly bike] #558930
08/18/14 9:02 pm
08/18/14 9:02 pm
Joined: Nov 2011
Posts: 4,737
U.S.
Magnetoman Offline

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Originally Posted by Hillbilly bike
...if all else is the equal.
Unfortunately, it's not. The flow volume through a given jet depend on fuel density and viscosity. Both of these differ significantly for different fuels at a given temperature and their temperature dependence differs as well. Besides, this is on top of John's point that without a precision measurement you don't know if your needle jet is too small or too large to begin with.

Re: Slide Cutaway at altitude [Re: aviator79] #558935
08/18/14 10:17 pm
08/18/14 10:17 pm
Joined: Mar 2005
Posts: 10,221
Boston, Massachusetts
J
John Healy Offline

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Joined: Mar 2005
Posts: 10,221
Boston, Massachusetts
Quote
E10 fuel has a slightly lower stoichiometric point than non ethanol gasoline so it's going to be a tad leaner if all else is the equal.


Which with my experience with AMAL's that only get richer at lower throttle openings due to wear of the needle jet, is a GOOD thing, not bad. Now some will jump in here and mention slide wear compensating, but if the carb isn't over tightened slide wear is not an over riding factor.

Whether you choose to believe it or not just because AMAL is stamped on a needle jet does not prove that it was it made by AMAL... That's just a fact. If someone wants to stop by I will be glad to show you some. Just because 106 is stamped on the jet does not mean that it measure .106", that is just a sad fact.

When you make a change, and you don't get the results you expect, it is time to go one step farther and ask some questions. In this case, with the history of poorly made and calibrated needle jets that are actually more available than the original AMAL ones it is IMHO time to start measuring. Unlike the main jet that is calibrated by flowing on a manometer calibrated by a standard the needle jet is calibrated by size.

This is what started this thread. A change was made that is commonly done by people who live at 5,000 feet and above and the expected result was obtained.


Re: Slide Cutaway at altitude [Re: NickL] #558958
08/19/14 7:20 am
08/19/14 7:20 am
Joined: Oct 2012
Posts: 4,018
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Originally Posted by NickL
I think fuel density/specific gravity has an input with jetting as well as e-content.
There were a few tests done with 98 octane over in the uk some years ago and some manufacturers of'super' 98 were slated as it's ok with compensating engine management but hopeless with carburation,
temperature compensation is one factor. I tend to stick with BP 98 as it was always the benchmark fuel in the tests. Although i'm probably well out of date now.


I'm aware of specific gravity from the VP fuel used in my race bike. Once the bike is jetted properly a change in SG will affect the A/F ratio. During the race meets many guys cover the fuel tank to keep fuel temperature constant.
On the street with pump fuel you have no idea what's coming out of the dispenser nozzle.The alcohol content varies,water in the fuel affect the A/F ratio. Ethanol absorbs water and the very slight water present in storage tanks can cause the ethanol to drop out of the gasoline. Since the ethanol is a octane booster/oxygenater you now have a different fuel... Any attempt at jetting is going to be a compromise...
And my bike might be the same spec as your but that doesn't always mean your jetting is the best for mine...But I'm not saying accurately checking jets sizes isn't important...it is



I ride dinosaurs that eat money
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