Small bore 2 cycle engines.

[John Noonan]

Bones,

Yes the RZ350 was sold in the states..

Please tell "E" we said hello.

John

[kiwi]

remember also that you can bore to the top of your cc class then .020 over that ---in the case of the yz 250 you could bore it .025 over and still be ok   ---                                            willie buchta

So is a 1363 cc Busa legal for the 1350 class? They are an 83mm bore. Displacement with  an 83mm - 0.020" (82.5mm) would be 1347cc.

[Nortonist 592]

remember also that you can bore to the top of your cc class then .020 over that ---in the case of the yz 250 you could bore it .025 over and still be ok   ---                                            willie buchta

So is a 1363 cc Busa legal for the 1350 class? They are an 83mm bore. Displacement with  an 83mm - 0.020" (82.5mm) would be 1347cc.

Boring usually makes a hole bigger.  You can't deduct to overbore allowance and make the hole smaller

[sheribuchta]

7.B.13 engine size   displacement shall be greater than the maximum allowable for the next lower class. To permit minor reconditioning of worn cylinder blocks in classes other than production, it is permitted to increase cylinder bore diameter .020 in.(.508 mm) Beyond that which provides maximum displacement for the class. In all cases, the resulting displacement shall be exceeded to qualify for the next higher class. The .020 in.(.508mm) will be discounted for record certification and will be noted on the certification card and in the log book.
That's on page 106 of the 2010 SCTA Rulebook.

[kiwi]

So if I run in 1350 class with a 1347cc engine (82.5mm bore) and then damage a cylinder and bore it out 0.020" (83mm) is it still in the 1350 class or not?

[sheribuchta]

kiwi  YES  you are allowed 1350 cc plus a .020 in. overbore ---i will give you an example on the engine i run-
bore 3.50 stroke 3.125 in.=60.1320 cu in or 985.383 cc    stock bore and stroke
bore 3.52 stroke 3.125 in.=60.1282 cu.in. or 996.6770      .020 in. overbore  still under 1000 cc
bore 3.40 stroke 3.125 in.=61.5143 cu.in. or 1008.0348     still legal in the 1000cc class if you discount the .020 in bore---just make sure you note the bore and displacement in your log book--and remember we arnt talking about production---and the vintage class allows a .050 bore above the class limit  --the total gained was 22cc or 1 1/3 cu in--on my engine thats about 2 hp in the gas class                 willie buchta