SX/SXi/SXi Pro a bunch of 750 top end questions!!!

i have a 94 750 small pin with a factory wet pipe,a westcoast head which i cant find gaskets for with i think 29 cc domes, a msd enhancer,single kehin carb 38mm i think but i broke it down for some hull fixin and i want to put pistons in it.ive seen that poeple put 82mm in them but will i have timing or detination problems from more compression?and will i need a bigger carb?some people say to run a timing advance,some dont?i think my compression was around 160 when i broke it down.could use any help i can get and also i live in central florida and would love to know if theres some good shops around...
 

98SXIPRO

One Of A K1nd
Location
The Bay Area
changing the piston size shouldn't change much. u will still get the same compression since ur not changing the dome size at all, so jetting should be the same. timing advance should be fine, the stock small pins were conservative on timing. the MSD enhancer adds a few degrees, and the timing advance adds a few more. (the SXI Pros [big pin] had more factory timing advance, which is where it became more of a concern) so you should be fine. compression is 150psi on a stock motor. at 160, ur more than fine. at 180-185 you should be running at least 91 octane, any higher and u should consider a race gas/premium gas mix.
 
Location
dfw
You will never get that Westcoast head to seal, especially larger bore sizes. Use a stock SXR head with that low port cylinder.
 
thanks for the tips guys...do you think the 82mm pistons is a smart choice?just worried about overheating problems and putting to much stress on the crank.and could i use like an ada head for a sxr cause i think my friend has one sitting around?
 

tor*p*do

Squarenose FTW
Site Supporter
Location
NW NC
ada head for 750 and 800 arw the same, except for the domes
check that it has the right size domes
I would not bore up and replace pistons unless it needs it (warm sleeve, grooves, bad pistosn, etc.)
that little bit of overbore doesnt do a whole lot performance wise
 
when i pulled it apart the sleeves and pistons look fine,no grooves but one of the pistons had a little bit of small craters by the exhaust side.the wrist pins dont look bad and i dont really feel any play on a straight pull on the rods but quite a bit of side play but i know your suppose to have some i just dont know how much...i might just throw it back together and ride it
 

tor*p*do

Squarenose FTW
Site Supporter
Location
NW NC
post pictures of piston crowns for advice
as long as your fingernail doesnt feel grooves in the sleeves they should be OK
a quick hone, new wrist pin bearings (a must), rings, gaskets, seals and reassemble
 
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