Jet Kit Calculator Techincal

How does the CarbJetKit jet Kit Calculator work?


The Calculator is the only existing tool to determine what Jet Kit is needed for your Motorcycle considering altitude, ambient temperature and applied intake and or exhaust modifications.

This being said, the CarbJetKit Jet Kit Calculator allows you to purchase a Jet Kit fit for your bike without the need to buy a kit that simply suplies multiple jets etc.. therefor saving you not just a lot of Money, but also a lot of tinkering hours.


Let's get to the point on how the carbJetKit Calculator really works.

First you need to know that all bikes are factory set to run at sea level, at 68 dergrees Fahrenheit and with no intake or exhaust modifications done.  At this they will still run slightly Lean!

Based of this, the CarbJetKit Calculator will factor in the altitude and ambient temperature and then give you the options to choose between the modifications you made to your bike, presenting you with the optimal Jet Kit for your Bike.

To establish the altitude correction factor, we did take a look at how air pressure and elevation are in relationship.

We concluded that with increased altitude, the air pressure drops as indicated in the chart below.

elevation correction jet kit calculator





















With a decreased air pressure, the oxygen concentration also drops relatively, therefor making your bike run richer in higher altitudes.

A similar conclusion can be made for the relationship between temperature and oxygen concentration, meaning that at higher temperatures the bike will run richer.

For both, we translated the charts in to correction factors and applied it in to  the Poisuelles law to calculate the new value for your bikes main and pilot jets.

This method is extremely accurate with regards to pressure changes due to the altitude and to temperature changes, but one shortfall is that you will need the altitude of the region you plan on riding, but we provided a link on the Jet Kit Calculator pages where you can get this information instantly, so it is the perfect method of determining your jet sizes!

At this point we use a second set of correction factors to allow for jet size adjustments in regards to intake and or exhaust modifications made. We decided that we needed to create 3 categories as follows;

for no or light modification
eg. stock airfilter and no exhaust mod, stock air filter and exhaust mod, k&N air filter and no exhaust mod

for moderate modification
eg.k&N air filter and exhaust mod, k&N air filter and light aftermarket exhaust

for Heavy modification
eg. K&N air filter and aftermarket exhaust. or basicly an open exhaust

for Ultra heavy modification

 eg. high flow intake (EX: Thunder Torornado or Thunder 360) and full open exhaust.

Ue our Bike specific calculators where all information exept for altitude and temperature is already being accaunted for.


I ordered a kit from you and rejetted, using 108 mains, 42 slow jets and added 2 shims to the one already there, for total of 3 shims per carb. (stock air box with K&N filter, Cobra drag exhaust)... I now want to remove baffles from the Cobra drags, and change my main jets to #112 as you recommend. Do I leave in all 3 shims per carb or should I remove 1 from each carb? I will be running #112 main jets, #42 slow jets, K&N filter and open exhaust (no baffles). Is this the way to go? The carbs are difficult to remove on my bike (1999 Honda VF750 Magna) and want to get it right so I don't have to remove them again.. thanks.
I previously ordered a kit from your company and installed it on my 2000 Valkyrie. I am making some new changes to my exhaust system.

In researching I have discovered some information that I need verified. I am not sure I was sent the correct kit originally but I made it work and the bike has been running fine.

Previously I had added a K and N filter to a stock filter box, and modified the stock exhaust. Then ordered a jet kit from your company - order number 3059. item# 639311021382. I ended up having to adjust the jet to 1 1/4 turns to get proper performance.

At this time I am changing out my stock pipes to Cobra exhaust with baffles.

Please confirm if the jet kit I currently have (referenced above) is the correct kit for the Cobra pipes.

Currently installed kit is 110 mains, #38 pilot, and 2 shims per carb. ( there was already 1 shim already on the carb, making it a total of 3 per carb)

Do I need a different kit or can I just adjust the mixture screw? Please advise.

With current set up, I started at 1 1/2 turns and reduced it to 1 1/4 turns. Because plugs were sooty at 1 1/2

Additional question... If i decide to remove the baffles, what jets should I use?

Please respond to or call 813-659-2524 after 5pm EST

I would like to have a phone number if possible to discuss this with a technician.

Dean D'Errico

Hello dean,

we emailed you with the answers to your questions.
Great tool. Saves time and money. Thanks
same bike replaced all parts sent, 115 and 120 mains, #42 pilot, and 2 shims each. k&n filter, cobra slashcut classics (made with non removable baffles. I'm getting soot both pipes and more soot on the front plugs than the rear. A/F screws out 2 turns. Runs fine just getting soot.
Hello all, thinking of rejetting.
Tried to order what calculator said I need and keep getting this...
No such product 'c239312222451'
I then tried to order the jets...Mains-122...Pilot-45...I could do the mains,,,but not the pilots...wasn't sure what 45's i need...0-100 sea level...40 tob 75 temp...stock air filters with baffels back plate drilled out...I believe my bike is a califoria model...I have something this thing under the radiator that my 93 vulcan 1500 didn't have...if someone from here contacts me to help me out...I would said that's excellent service...we will see...??? Thanks
ADMIN: WE contacted you by email. Thanks for informing us about the issue. It has been resolved.
This time its for my 2 buddys who are bobbing up a pair of cx 500.. Easyer and cheaper if we order the kits together :-)
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