Yamato 102, 202 302

[Steve Crabtree]

Whats the difference between the Yamato's they seem to be the same bore and stroke and can you explain the difference between 25 Mod and C Mod if the same Yamato engine is being used for both classes. Please explain completely as I don't understand the difference yet, I need educated . I've been out of racing since 1980 and back then there was just a Yamato 80.

[seanp3]

ok - I'm no expert on this, but since no one else has jumped in here....

The 302 is the current production motor that will eventually replace the 102. The 302 has electronic ignition, the 102 doesn't, and the 302 tower is a little over 1" shorter than the 102. Both motors are fairly competetive with each other and are mainly for the C stock classes. Some say the 102 has little better top end, and the 302 a little better bottom end. Both are legal C stock motors at this time.

I don't run the 25 class so someone else will have to fill you in there. I believe a 9/16" restrictor plate is used for either the 102 or the 302 if you want to use the motor in the 25 class.

[dcrummett]

In NBRA the 25 Mod class now allows the Yamato 102, 202 or 302 powerhead with stock internal specifications, but with an open (or any) exhaust. In C-Mod, the exhaust can is to be run through an expansion chamber.

The classes are blurring a little here, but the original 25 Mod class was reserved for only the 102 (we just opened it up for anyone with a Y who wanted to mess with it.)

So, with a stocker and a C-Mod, I hope to run in CSH, 25Mod and C-Mod in 2008.

Dan
O49

[racer121M]

Dan...help me out here...can I run my stock 302 with a stock exhaust as a 25 mod using the 9/16 restrictor?

[Steve Crabtree]

Is the restrictor plate something that goes between the carburator and crankcase?

[dcrummett]

Steve, yes, a restrictor plate fits between the carburetor and the reed cage housing, but the only restrictor plates we use in NBRA are in the novice class.

Dan
O49

[ryan_4z]

The restrictor plate in reference is only used in APBA SO's 25ssR class. I deduce that NBRA's 25 mod class is a close match to APBA's C mod class.

[David_L6]

I no longer keep up with the rules of classes that I don't race so I may not be 100% accurate here but I think that the NBRA 25 Mod rules are as follows.

Stock powerhead, any make lower unit of any gear ratio (no overdrive), any kind of exhaust (open megaphones are permitted), any kind of tower housing with no length/height restrictions, 400 pound minimum weight for the hydros. They are faster than the C Mods. Brian Payne raced his at the PRO Nationals in RB Hydro and did very well (2nd?, 3rd?).