LO206 main jet tech question

SteveNoCo

New member
I'm looking to get back into karting next year and I'm doing some research.

I live in Colorado and I know that some have said that there is plenty of adjustability in the carb settings and this is not necessary. But I'm interested in finding a #95 main jet that is on the smaller side. It just seems like I will have more adjustability if I can find a smaller jet for the altitude. The rules say "0.036 go, 0.039 no go". With out buying a whole tech kit I just want to buy a few pin gauges to find a legal jet. So the 0.036 is that the size of the pin gauge or the size on the hole in the jet? So I guess I'm really asking do I need an 0.036 pin gauge or a 0.035 pin gauge to check for an 0.036 jet size?

Thanks for the help, Steve
 
The .036 MUST go, you would want a .036" pin gauge, and possibly a .035" pin gauge for the "no-go" on the small side.
Finding the smallest one would be a chore (even with ordering them in bulk.) There's just not a whole lot of difference in them (slight, yes, but not enough to sort in my opinion.) You can definitely find carbs that will work better at your elevation (ie air side is different - consider the newer Briggs logo carbs.) Again, sorting can become extremely expensive with little return on investment considering that you can still change your needle clip height the equivalent (or more) than the legal range of main jets you are able to come up with. ;)

-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
28 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
If the jet is stock the .035" will pass through no problem, if it is close you will feel the >036" snug and a .037 will not enter.
 
MSC Industrial Supply
Tel 800-645-7270

https://www.mscdirect.com/browse/tn...311&searchterm=individual+plug+and+pin+gauges

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Diameter of Measurement (Decimal Inch) 0.0350

Here is the part number for the main jet: 555742
Here's the part number for the idle jet: 555594

Good luck, Have fun:)
 
The .036 MUST go, you would want a .036" pin gauge, and possibly a .035" pin gauge for the "no-go" on the small side.
Finding the smallest one would be a chore (even with ordering them in bulk.) There's just not a whole lot of difference in them (slight, yes, but not enough to sort in my opinion.) You can definitely find carbs that will work better at your elevation (ie air side is different - consider the newer Briggs logo carbs.) Again, sorting can become extremely expensive with little return on investment considering that you can still change your needle clip height the equivalent (or more) than the legal range of main jets you are able to come up with. ;)

-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
28 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
JUDGE TOOL HAS ANYTHING YOU WANT PLUS AND MINUS Z GUAGES SOLD INDIVIDUALLY AT $5.00 EACH
 
Be aware, pin gauges come in plus or minus sets, .0002 and .0001 tolerance. Myers gauges are good. I can't vouch personally for any others. Pin gauge sets come in .001" increments. I have used sets that come in .0001 increments, sets of 10 gauges. Very expensive.
You can buy reamer's between .035" and .036" from MSC. I'm not looking at the book right now but there might be 3 or 4 sizes between if you look at the numerical and metric sizes.

I forget the name, but there's a carburetor maker in Europe that sells jets for their carbs that are numbered in flow rates, rather than sizes. They test every jet they make for actual flow.

I used to work for tTruax engineering, they make rocket engines. We once had 200 injector jets made on a Swiss CNC lathe. Flow testing showed that there was about 13 or 14 different flow rates amongst those 200 jets. Not big differences, but differences. It was a fairly crude testing method. We flowed a gallon of water and measured the time it took to flow through each jet. The more water you flow, the less significant the timing error gets.

Comparing the difference between a .035" jet and a .036" jet you find this. To compensate for a 1% change in air density, you have to change the .035" jet size by .0002". Hard to justify the expense when trying to meet those numbers. There is an alternative.

By changing both jet sizes, high/low, flow rates can be reached between just changing the main jet. I have a spreadsheet for that.

alvinnunley62@gmail.com
 
If you're running the CKT you must run what is stated in the rules. They tried to have a LO of a leaner jet early on to accommodate for the higher altitude and were contacted by Briggs directly about that issue. Also, make sure you're running the stock needle. There's a variant needle that isn't legal in the CKT so make sure you double check yours.
Chuck above is a great contract to talk to. Him and Dustin are very well versed and can help you out. Freezeman on here is also a great contact if you have any questions.
 
It is odd when 3 year old post come back up.
No. Honestly if you start a new one with same question you get roasted or "Al'd" to death.

Some of us are learning, supporting and love running our 206's so it is nice to see the community helping each other in my opinion.

I have learned a lot by just reading what others already know or help explain.
 
JUDGE TOOL HAS ANYTHING YOU WANT PLUS AND MINUS Z GUAGES SOLD INDIVIDUALLY AT $5.00 EACH
I was referring to buying "jets" (not pin gauges) in bulk and checking them for variance in sizes since you have to run the stock jet in these engines. Keep in mind that you cannot purchase jet blanks and ream them yourself -- that will not fly in tech, (or at least it shouldn't) per the L206 rules.
 
From a tech standpoint, the jet needs to be stamped 36 and must not have a no-go .039 pass through.
jjchat, I think you meant to type "stamped 95"? Which represents .95 millimeter so .95mm X .03937= .0374015 inch.
I made timed water flow test bench out of a balance scale that measured the amount of time it takes to flow 1 pound of water through a jet.
The 7 .95 jets I tested took 7minututes and 40 seconds for the slowest one (leanest) with the fastest(richest) flowed at least a full minute faster with the others in-between. I was sort of interesting, I flowed the water in the same direction through the jet as the fuel would have to travel and used the same water level/pressure/weight at the beginning of each test. The crazy thing to me was when I did back to back tests of the same jet the second test would flow a little faster each time. It made me wonder if the jet was warming a bit from being flowed through or if the water was cleaning the inside surface of the jet. That testing was some years ago and this post got me to pull out my old jet kit. I wonder if they would flow slower now with some oxidation build up from time passing by.

Like Mac mentioned the gas needle is teched along with the emullsion tube holes and the next tech item to look at is the size of the main nozzle .101" minimum to .103 max. watch out for the alky pz main nozzles that are larger.
 
I was referring to buying "jets" (not pin gauges) in bulk and checking them for variance in sizes since you have to run the stock jet in these engines. Keep in mind that you cannot purchase jet blanks and ream them yourself -- that will not fly in tech, (or at least it shouldn't) per the L206 rules.
Better to check them for variance in flow. How do you plan to check them for variance in size?
 
You could do like several people are doing now.

Order blank jets B&S 555639 (5 pack) and drill to desired size.

Then laser the proper "95" on the side.

I personally don't do this, as that is just way too much effort, for so little gain.
 
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