KEYSTER fuel tune-up kit “Keyster” has been made two large purposes: Troubleshootings and Tune-ups.
We must use fuel adjustment parts properly acording to purposes.
First, we mention adout Troubleshootings.
If the Air-Fuel mixing ratio (A/F) is not correct and engine peformance is not enough, it is better to change all items of carbutrtor parts contained in “Keyster” for old parts.
We recommend you to use each standard size (standing for "S") of fuel adjustment parts first.
If engine condition does not improve even after such treatment, try another size of parts aiming to get proper A/F.
Please refer to ≪Mechanism of "Keyster"≫ or you can find the way to select the right size part.
Traditional carburetor kits contain only standard size jets, so that they can not deal with these situation.
When any size of “Keyster” does not work to bring proper A/F, it is necessary to examine other devices and looseness of each jointed place.
If the engine does not perform good under apprppriate A/F, reason of trouble does not due to carburetors.

New type carubretor kit “Keyster” can be used for tune-up as well.
Carubretor can not demonstrate its efficiency by itself, because it ia a supportive device of other equipment.
When moterbikes are modified to get higher perfomanse, “Keyster” is supremely helpful.
If modifications are done at airfilters,engines or mufflers, conditions of required miture gases will vary.
In these cases, only “Keyster” can offer apprppriate air-gas mixture.
Let us explain usage of “Keyster” in case of engine-boreups.
It is said that boreups is most difficult to controle the A/F effectually.
Boreup enlarge capacities of cylinders , so that it naturally require much more mixtures.
So, the makers of boreup kits commonly advice on users to chage the mainjets of carburetors for lager size by about 10.
Most of users follow this advice to change, but they often can not get satisfactory results.
Why is this happen?
Keyster analyzed this hard problems and got clear solution. We explain it step by step.
There ara two famous carburetor makers in japan: "K" and "M".
Most japanese moterbikes are mounted these maker's products.
Two makers use different rules to call jetsize each other.
This is the reason of huge trouble on tuning carburetors.

For exsample, mainjet #100 of "K" has a hole Φ1.00 in diameter and #110 has Φ1.10 in diameter.
In brief, jet size mean jet hole diameter.
It is very simple.
If the mainjet is exchanged from #100 to #110, the fuel supply increases about 19% (quantity of fuel is measured by our original method).
On the other hand, mainjet #100 of "M" has a hole Φ0.89 in diameter and #110 has Φ0.93 in diameter.
In this case, fuel supply increases only about 8%.
Therefore,advice of the boreup kit makers is not appropriate.
They must indicate different size increment according to carburetor makers. (We suppose "M"'s sizenumbers come from quantity of fuel flow.)
Keyster have considered all of these situations in the motorbike world and produced new carburetor tune-up kits “Keyster”.
You can get best engine performance by “Keyster”.
On airfilter or muffler changes, you shall realize same results.

“Keyster” leads you to get proper A/F when you try modifying the motorbikes.
However,sometime you may need amount of fuel flow rather than A/F.
For you can determein the jet size from the amount of fuel, we show you quantity of fuel supply ratio in "Fuel Tune-up Parts List" in the instruction which you can see by clicking.
We expect that theb modication kits makers will indicate the jet size with the quantity of fuel supply from our "Fuel Tune-up Parts List" in the near future.

Lastly, we must give a caution.
Too lean combustion occur baking engine in rare case.
So when you increse A/F very much, be careful enough.
Carburetor Tuning can give real joy and spice for motorbike enthusiasts.

Challenge modify your motorbike with our “Keyster”.

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