UIM · Fuel
The tuning tier that stays legal in the closed-list classes.
This page is UIM only, and the bodies do not agree. The same part under IHRA and IJSBA. Which one applies to you is decided by whoever sanctions the race you enter.
19 classes, grouped where the same rule gives the same answer rather than listed one by one, because an answer that holds for a class usually holds for every class that borrows its rules. 5 of them borrow another class’s rules and are marked below; for those, the link to the parent class is read from the categories table rather than stated in the rulebook. 8 publish no rule for this part and name no parent to borrow one from, and are grouped together at the end.
Legal 4 classes
Replaceable-type jets, needle valves and needle valve springs may be changed; choke may be removed provided it creates no additional air intake.
Legal 2 classes
Carburetors may be modified or aftermarket, so jets, needle valves and their springs may be changed, provided the carburetor does not vent or spill fuel, has no more venturis than cylinders and is not a slide type.
No rule, this is an open class 5 classes
No article covering this part. Free under the open-list reading of GP1.
No rule published for this class 8 classes
No component rules are published for this class and no single parent class is named, so this part cannot be answered for it. That is an absence in the rulebook, not a permission.
Carb jet kit, needle valve, needle valve spring: if the rule your class applies reads differently to you, or the rulebook has changed since this was read, ask. We answer with the section we read it from, or that we have not read it. Ask a rules question.
Every UIM class · where the rulebooks differ · checks on parts the shop sells · how this site reads a rulebook.
Fuel · two stroke · legal in 6 of 11 answered