4 Cycle Karting Forums - 2012 AKRA BP Engine Specs

12-08-11,, 08:11 AM

ARCkartracer

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2012 AKRA BP Engine Specs

Use of these Rules and Regulations require Tracks, Clubs, Promoters or Series be sanctioned by the American Kart Racing Association. Any other use is strictly prohibited without the express written consent of the American Kart Racing Association (AKRA).
The information posted here on 4cycle.com consists only of the engine specific technical data for the specific classes listed. There is considerable important information concerning general requirements, measurement procedures, class structures and tolerances that are only supplied in the printed rule book. A failure to comply with the rule book in its entirety may result in a disqualification. It is strongly suggested that racers obtain a copy of the complete book by contacting AKRA. No ruling appeal on any disqualification will be heard by AKRA unless the Track, Club, Promoter or Series involved is sanctioned by AKRA and the individual racer involved is a member of AKRA. www.akrainc.com

These rules take effect 1/1/2012

Quote:

BP (Builder Prepared) 6.5 OHV Fuel Methanol ONLY Approved Engine: 6.5 OHV 196cc clone engine modified only according to BP OHV Engine Spec. Tires are track/series option.

ENGINE SPEC SHEET FOR BP 6.5 OHV CLASS
Description: Single cylinder, 2-valve overhead 4-cycle engine. No aftermarket coatings of any type are permitted on any part of the engine (exception Blower Housing and Shrouds).

Cylinder Head Requirements: Stock cylinder head only. Machining of gasket surface is allowed. No addition of material in ports or to cylinder head allowed. Porting and / or grinding are not permitted. Valve seats may have two angles, 45 valve face and 30 top relief. Inside diameter of valve seats must be stock(Into .897 max ID and Ex .862 max ID). Valve seats must appear stock and must be in stock position and depth. Stock head bolts are required and all four are required. Head gasket/s maybe after market, must be of stock configuration, and gasket thickness non-tech. Depth check between the valves, front to back and side to side may not vary by more than .005 max. Cylinder head guide plate for pushrods must remain stock. No other alterations to the stock head are permitted.

Bore and Stroke: Stock bore is 2.685 and may be over bored to 2.718 Stroke is 2.123 +.010-.005.
Connecting Rod: Stock or Billet aluminum rods, with or without bearing inserts allowed. No titanium rods allowed. Rod length is a non tech item.

Combustion Chamber Volume: 25 cubic centimeter minimum, with piston at TDC, using prescribed procedure. The Liquid CC check is the official check (IF THE ENGINE FAILS THE CC LIQUID CHECK AT ANY TIME DURING THE TECH PROCEDURE IT MUST BE CALLED ILLEGAL).

Carburetor/Intake Requirements: Stock Huayi or RUI*ING carb. Venturi .625 NO-GO. Rear carb bore .751 NO-GO. Carb bore finish, non tech. Throttle shaft - .115 minimum. Butterfly - .037 minimum. Air Filter adapter of 1.375 max length allowed. No air rams. Pulse-type fuel pump is mandatory. Fuel pump must be pulsed from either the crankcase or the valve cover. Black phenolic carb insulator must be used. Choke assembly may be removed. Jets, air bleeds jets, and emulsion tubes are non-tech. Throttle shaft, washer, and butterfly must be stock and must be present, butterfly screw non tech. Stock intake runner gasket configuration only. One extra gasket may be used with restrictor plates. No other alterations are permitted.

Ignition system: Ignition timing is non tech. Stock ignition module only. No modifications of any type allowed. Sparkplug connector must be stock as from factory.

Piston Requirements: Must be stock dished piston with no modifications. Oversize Clone or Honda ZOT dished piston is allowed up to .035" oversize. Rings must appear stock and all rings must be installed. Piston may not pop out above cylinder deck.

Valve Train: Stock valve-train only in stock configuration except any single valve springs and valve spring shims are allowed. No additional support for rocker studs permitted. Valves must be one angle only, 45. No polishing, lightening or knife edging of valves (1mm min. margin). Valve length is non-tech. Outside face of valve head may not be below the combustion chamber floor. (i.e. dont sink the valves) Valve cover may be drilled for fuel pump pulse fitting, otherwise, it must remain unaltered. Valve cover gasket is non-tech.

Camshaft Requirements: Stock camshaft cores only, ez-spin assy must remain as stock. Duration check for Intake and Exhaust lobes (taken off pushrod) . Intake duration of 248 degrees at .050 lift/107 degrees at .200 lift. Exhaust duration of 247 degrees at .050 lift/116 degrees at .200 lift. Max lift at the valve retainers, Intake .238 and exhaust .242 taken on valve spring retainer with zero lash. (To achieve zero valve lash for checking running lift, preload dial indicator by .001.)

Crankshaft Requirements: Stock, factory crankshaft only with stock, factory timing gear in factory location. No modifications to crankshaft allowed. Aftermarket steel main bearings of non self-aligning type, with or without seal are allowed. No ceramic bearings. Crankshaft Journal diameter is 1.180, 1.168 minimum.

Block Requirements: Stock Block, as cast and produced with no alterations or modifications other than those specifically permitted. Block head matting surface may be machined, however, no piston pop out is allowed. Blocks may NOT be welded for repairs. No addition of material to block (i.e. welding, jb weld, etc). All bolt bosses in block may be drilled and tapped for repairs or other uses. Additional side cover gaskets as required for crankshaft thrust are permitted. All parts associated with the governor and the low oil sensor may be removed, plugging any associated holes.

Flywheel: Approved SFI certified billet aluminum flywheel only. No machining or alteration of any kind allowed. Minimum weight for flywheel is 3.3 lbs. Any timing key or no key at all may be used. A flat washer or spacer may be used, and is recommended, between the flywheel and the nut. Handheld electric starter may be used, but compression release mechanism must remain on camshaft.
Current Approved flywheels: ARC 6619, ARC 6618, Raceseng Flywheels RSP-13-075 Rewheel NF- S1 & RSP-13-077 Rewheel F-S1.

Header and Muffler Requirements: Header Pipe Length: Minimum 18- Maximum 22. Silencer must be a RLV 91_L type with .1285 no-go hole. Header must be securely wrapped from flange to muffler prior to the race. Exhaust Pipe must be double nutted or safety wired and silencer must be supported by clamped on brace to secure it in place.

ANY corrections, additions, or changes to these rules are submitted to the rules committee and approved PRIOR to being posted here. Each edit will be documented below.

Edited on 12-16-11, at 06:32 AM.

12-08-11,, 08:13 AM

ARCkartracer

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Re: 2012 AKRA BP Engine Specs

The changes from the PRINTED 2011 AKRA book are in blue text.

Edited on 12-09-11, at 07:53 AM.

12-16-11,, 06:31 AM

ARCkartracer

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Re: 2012 AKRA BP Engine Specs

Greetings

After all of the recent phone calls and all the defacation hitting the rotary oscillator on this measurement check we are going back to a cc check only. See the final version.

Thanks,

Bill

Was
Combustion Chamber Volume: 25 cubic centimeter minimum with piston at TDC using procedure posted below. The CC check is the official check, however when a burett is not available the following Optional check may be used (optional check not intended to replace or override the CC check). Optional volume check, Depth of piston(checked outside edges, across wrist pin) + head gasket thickness + depth of head measured between valves = .280 minimum.

Final Text
Combustion chamber volume: 25 cubic centimeter minimum, with piston at TDC, using prescribed procedure. The Liquid CC check is the official check (IF THE ENGINE FAILS THE CC LIQUID CHECK AT ANY TIME DURING THE TECH PROCEDURE IT MUST BE CALLED ILLEGAL).

POST #1 HAS BEEN EDITED TO REFLECT THIS CHANGE