SX/SXi/SXi Pro 800sxr swap into my sx hull?

[reidmtb]

hi all,

I'm at a point in my build where I have to figure out my engine situation. Here are my options:

1) I currently have a 750 sp with a blown crank (cylinders/head are good). Initially, I wanted to go the route of rebuilding/porting the 750 but with the crank rebuild, porting, head decking, etc... it will cost a little over $1,000 to complete. Ive been stockpiling parts for a while, mainly a full PJS pipe, 46's, Vforces, etc... But still have yet to send the crank and motor off.

2) Buy an sxr 800 motor and swap it in. Ive found some complete ones in good shape in the $1,100 range.

My questions are: What are the advantages and disadvantages of an 800 swap? Will my PJS wrap-around pipe work for it? What would you do in my situation? I feel like having a newer motor will give me more access to parts down the line, and for roughly the same cost, i don't see why an 800 swap wouldn't work. Thank you in advance

 

[kevbo]

Big pin 750s and 800s are nearly the same engine. They all have the same crankshaft. 800 cases are more desirable since they have some additional factory porting. Big pin 750s all have higher exhaust ports than the 800 cylinders. Get a new crank and find a nice case and cylinder. Small pin 750 cylinders will work just make sure the liner clears the crankwheels. The real performance difference is in the port height, the high port cylinders may struggle to get on the pipe. You will want to use a big pin cdi box, small pin cdi has a flatter timing curve which is not desirable. A complete 800 engine is ideal if its condition is good.

 

[TheBuzzard]

Sxr has 80 hp stock and BP 750 has 75. I wouldn't chase any high dollar 800 motor when 750s are much cheaper. 800 cases are different but nothing that some simple porting wouldn't equal up. 750 ported cyl would out perform any 800

 

[roman]

What stamp is your small pin cylinder? If you have one that is not stamped, I believe that is the ideal cylinder for freestyle for the 750's.
some people also say putting big pin cases on the low port small pin cylinders is the ticket. Not sure what crank you use or what other mods its requires or what the exact recipe is there.

But if we are comparing getting a totally rebuilt and ported for freestyle no stamp 750.....vs a used 800 that you will not rebuild.....I would go with the ported (not too radically) fully rebuilt 750. It should in theory last longer given the fact that everything is new. It will also rip really good I bet. Wont have the topend of the 800, but lets bet honest....the sx/sxi hull sucks at high speed.

If you get the 800, youll probably go down the road of.....you atleast need to freshen it with new gaskets and seals.......that's almost a must......then you will open it and go...well I have it open so maybe fresh pistons are a good idea.....and then its like.....might aswell bore the cylinders to get out these light scratches.