Big pin VS Small pin for engine swap X2...

[Cannibal]

Sorry, not going to Yamaha power it....:doh:

Looking a 2 candidates tomorrow for an engine swap.

1) 92 750SX recently rebuilt (stock bore) and ported (he doesn't know to what extent but thinks it might be more "race"), SXi head, advance plate, stock single carb

2) 98 750SXi Pro. Fresh rebuild (.5mm over and Pro-x pistons), stock porting, R&D head, stock dual carb, lightened flywheel

I'd probably be running my 650 electrics on them, so engine for engine, what am I really going to want?

Oh ya, I ride mostly flat water and will be freeriding too and I weigh about 225lbs.

 

[Crab]

1

 

[Cannibal]

Simple as that huh?

 

[Jayski]

j

650 electrics you want small pin right.. Much easer to do.

 

[WFO Speedracer]

Big pin has much less bottom end snap,its mostly mid range and top end,go with the small pin

 

[BombThreat]

oic! good to know

 

[djkorn1]

Big pin and an SXR cyllinder and you'll rip.....

...but out of those options, go with one and get a LARGE carb, because it is gonna be a dog with that one carb.

 

[Cannibal]

Things got pushed back to Sunday...

I know about the better bottom end of the small pin (41-43mm exhaust height depending on model), and the better top end of the big pin (39mm exhaust height). The reason I considered the big pin was because of the options of better porting with SXR cylinders and such. I wouldn't be able to do engine mods for a while, but if the big pin toasted, it would either get SXR liners, or a whole SXR cylinder (depends on availability and cost).

Big pin is 75hp while small pin is 63hp. Hell my 95 650 is 57hp. Not a huge jump stock for stock from 650 to small pin, but a better building block. The major difference in big pin to small pin HP is the intake. A single 40mm Keihin compared to double 40mm I body Mikunis. Luckily stock dual SXi intakes are available cheap ($150), but an SXR intake would be better with dual 40mm SBNs but more coin.

I've never been able to compare big vs small on the performance.

Thanks!

 

[WFO Speedracer]

You are correct in that there is no huge difference from 650-750 small pin in stock form,I have ridden 650 powered skis that would eat a small pin powered skis lunch.The main issue with the power of the small pin engine is the crappy stock exhaust pipe,it is quite restrictrive,change the exhuast pipe to a B pipe or even a Westcoast or Coffman pipe and you get a major boost in power,then the 750 small pin swap makes sense.