KEYSTER fuel tune-up kit “Keyster” has been made two large purposes: Trouble-shootings and Tune-ups.
We must use fuel adjustment parts properly according to purposes.
First, we mention about Trouble-shootings.
If the Air-Fuel mixing ratio (A/F) is not correct and engine performance is not enough, it is better to change all items of carburetor 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 appropriate A/F, reason of trouble does not due to carburetors.

New type carburetor kit “Keyster” can be used for tune-up as well.
Carburetor can not demonstrate its efficiency by itself, because it ia a supportive device of other equipment.
When motorcycles are modified to get higher performance, “Keyster” is supremely helpful.
If modifications are done at air filters, engines or mufflers, conditions of required mixture gases will vary.
In these cases, only “Keyster” can offer appropriate air-gas mixture.
Let us explain usage of “Keyster” in case of engine bore-ups.
It is said that bore-ups is most difficult to control the A/F effectually.
Bore-up enlarge capacities of cylinders , so that it naturally require much more mixtures.
So, the makers of bore-up kits commonly advice on users to change the main-jets 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 motorcycles are mounted the products of these makers.
Two makers use different rules to call jet size each other.
This is the reason of huge trouble on tuning carburetors.

For example, main-jet #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 main-jet 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, main-jet #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 bore-up kit makers is not appropriate.
They must indicate different size increment according to carburetor makers. (We suppose "M"'s size numbers come from quantity of fuel flow.)
Keyster have considered all of these situations in the motorcycle world and produced new carburetor tune-up kits “Keyster”.
You can get best engine performance by “Keyster”.
On air filter or muffler changes, you shall realize same results.

“Keyster” leads you to get proper A/F when you try modifying the motorcycles.
However,sometime you may need amount of fuel flow rather than A/F.
For you can determine 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 increase A/F very much, be careful enough.
Carburetor Tuning can give real joy and spice for motorcycle enthusiasts.

Challenge modify your motorcycle with our “Keyster”.

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