Here You Go.......
RLV B91 series silencers are the only approved 4-cycle silencers. Silencer must be stock,
unaltered as delivered by RLV. All B91 series silencers, outside diameter 2.240 inch
maximum. All B91 silencers must exit aft of the fuel tank and forward of the rear
bumper. All exhaust systems must be constructed in a manner that directs all exhaust
gasses away from the driver and towards the rear of the kart. New RLV B91 silencers with safety cable attachment device allowed, Note: all B91 silencers must be so equipped with safety device by January 1, 2016. Add-on safety devices will also be allowed.
Important Note: All parts must be Box Stock factory production parts unless otherwise
specified in this rules manual. No machining or alteration of parts is allowed unless
specifically noted. All parts will be subject to a comparison to a know Box Stock part (when
performing a "stock part" comparison check it is recommended to use a + /- .005” tolerance). Tumbling of engine parts is strickly prohibited. Engine will be teched as raced. There will also be a $200 claiming rule in place for this engine or $350 if engine has billet flywheel installed (Track or Series Option).
Refusing to accept the claimer will result in immediate disqualification of competitor along with forfeiture of any points earned to date in class. Competitor will also not be allowed to compete any longer in that class.
Cylinder Head Requirements: Must be OEM casting only. Porting and / or grinding are not permitted. Valve seats may have up to three angles, 45 degrees valve face and 30 degrees top relief and 60 degree bottom relief. Intake seat maximum ID .897”, Exhaust seat maximum ID .862”. Outside face of valve may not be below floor of combustion chamber (i.e. don’t sink the valves). Stock head bolts only, must have four. Head gasket/s maybe after market, must be of stock configuration, gasket thickness is a non tech item, sealer allowed to insure proper seal. Depth check between the valves, front to back and side to side may not vary by more than .005” max. No copper or aluminum gaskets allowed. Any stock configuration exhaust gasket allowed, sealer permitted, Header may also be run without gasket, sealer only. Allen head bolts permitted on Header to head.
Block Requirements: Oil drain hole between lifters .251” no go. Any type side cover fastener and lock washer permitted, must be original size, sealer permitted.
Carburetor requirements: Huayi OR RUI*ING model carb only. Carb to intake sealer is
gasket only no other sealer allowed. Choke must be as supplied from factory, but may
be fixed to stay in open position (Choke area must remain as cast). Venturi .615” NO-GO. Venturi maybe machined to spec, no polishing permitted and all transitions must remain stock in and out of venturi. Rear carb bore .751” NO-GO. Carb bore at rear of carb .750” maximum depth (This measurement is taken from the flat surface on the rear of the carb down to the circular ridge at venturi edge). Main fuel jet .042” NO-GO. Low speed idle jet is a Non Tech item. Stock emulsion tube must be used and unaltered, .066’ max ID (no pass through). Side holes in E-Tube 4 holes in bottom section and 20 holes in top section max. Minimum E-Tube length 1.092”. Side holes in e-tube diameter .036” no go. Throttle shaft - .115” minimum. Stop arm of throttle shaft maybe filed to adjust for butterfly position. Butterfly - .037” minimum. Aftermarket air filter adapter allowed (max length of 1.375). Black Phenolic spacer must be flat across entire gasket mating surface with a minimum thichness on gasket surface of .265”. Deburring of inlet track allowed to remove flashing . Any attempt of inducting air into the intake port other than through the carburetor bore is not allowed. Surface finish of phenolic spacer inlet track, non tech..
Valve Train: Stock valve cover only with any stock configuration gasket, sealer allowed.
Factory stock rocker arms 1:1 ratio and push rods only. Surface finish of contact area of rocker arm to valve
stem , non tech, to adjust for proper lift running lift. Stock steel/stainless nitrate coated valves only 45 degree angle only both
valves with a minimum weight of 21 grams each valve, Intake valve Max OD .982” +/- .005” and Exhaust valve Max OD
.945” +/- .005”, no modifications allowed. Single valve springs only. (Installed Height for valve
springs .815”, must be checked by using the .815” spring must go gauge with retainer seal
and shims in place on intake an exhaust valve if used.) Shims may be used to achieve .815” Installed height, maximum thickness of shims used .045”, any combination of valve seal and spring shims allowed. Prescribed check procedure as follows – Remove valve spring, reinstall spring retainer and shims, insert .815” must go gauge in spring location. Gauge must go in both locations Intake and Exhaust with any allowed retainers and shims in place, as raced, during check procedure. Max wire diameter on spring wire is .071” with a maximum tension of 10.8 lbs. at a height of .850”, and a maximum tension of 18 lbs at
.650”. Each spring is to be checked using a
.750”height by .800”width plate gauge and a .250” (square) no-go gauge to check the
center spacing of the spring coils while inserted in the plate gauge. Prescribed check
procedure as follows – Insert the spring in the .750” X .800” plate gauge (spring must be
centered in plate gauge and must fit inside of gauge with the ends of the spring wires
perpendicular to the plate ). Once inserted in the plate gauge take the .250” no-go gage
and check the center coil spacing on both sides. The .250” no-go gauge must be parallel
to the spring wire and perpendicular to the center of the spring when checking. The .250”
no-go must pass check on at least one side of the spring. This check is to be performed
after the 10.8/lb , 18/lb check, and .071 max wire diameter check have been performed.
Ends of the valve springs may be sanded to help meet spring checks. Lash cap on exhaust
valve only. Valve stem seal allowed on Intake and Exhaust valve. Minimum thickness of Intake retainer .225” , Exhaust retainer .245”. BS lifters only, no
modifications allowed. Over-all length of push rod 5.285” max. Weight check lifters 18 grams min and push rods 9 grams min.
Piston and Rings: Piston must be unaltered Box Stock only. Overall piston length 1.935” max, 1.920” min and from top of wrist pin to top of piston .580” max. Arrow on
top of piston must be pointed toward valves/lifters. Overall length wrist pin 2.100” min, inside diameter .550” max.
Top ring and middle ring .115” max width, .060” max thickness.) Filing of ring end gaps permitted including oil
expander, max end gap .040”(top 2 rings only). Lapping of rings permitted for proper seal. Piston ring must be in one
piece(unbroken) when presented for tech. Piston rings must be self supporting in cylinder bore and concentric to
cylinder bore. Oil ring assembly must be self supporting in cylinder bore when checked installed on piston
with connecting rod attached.
Connecting Rod: New stock performance CAST rod allowed. Length from top of journal to bottom of wrist pin hole 2.375 max. and 2.350 Min. Honing of journal end and wrist pin hole permitted. Surfaces to remain flat.
Oil hole size : .173 no go
Header and Muffler Requirements: Any single stage, one-piece header made from .750”
OD steel tubing, with the RLV Mini B-91 Silencer installed at the end of pipe. The B-91
Silencer must be tread fitted to the pipe end. The entire exhaust pipe including the muffler
is 15” max length and 10” min length. Exhaust Pipe must be double nutted or safety wired
and silencer must be supported by clamped on brace to secure it in place. Pro Box Stock header length 16 ½” min and 20 ½” max (measured on inside of pipe with ¼” steel tape). Sealer may be used to assist gasket seal. Header may also be run without gasket, sealer only.
Here are the AKRA 2014 Rules that are going to the printer. As in the past, if there are any changes that must be made, AKRA will take a look at them and make a decision on it. Any changes that should be made will be submitted to the steering committee that AKRA is going to select at the Charlotte Show in January. As in the past, if there is a change, you the karter will be notified here on Bob's. AKRA would like to say a big "Thank You" to all of you have given input to the changes for 2014. AKRA and myself are looking forward to meeting as many of you as possible at Charlotte. Again, Thank You