It's about time to rebuild the engine on my '92 sportster 1200. I want to get more cc's. What's the max I can bore my engine out to? If get new jugs can I get even bigger? After consulting with a few places since I don't have efi, a turbo system isn't practical with my engine so now I'm looking into max natural aspiration.

 

I think you can only go to about 1250. But cams, higher compression, valves & headwork with tuning can get you well over the 100hp mark. And if you wanting to drag race or the extra bump you an always spray it some.

 

if you are willing to re-move the engine and have the cases worked, you can get into the 89-90 inch range with 3 3/4 or 3 13/16 pistons.
if you are willing to remove the engine and pull the crank you can get much bigger, it's really a money thing, have much do you want to spend? mine is 89 inchs, bore and stroked. stroker flywheels and 3 5/8 cylinder bores, the stroker path usually leads to much more torque, but you can get some really good horsepower without the stroke, with the really big bore, you just have to have the cases machined to accept the larger cylinder spigots.
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How crazy would a 3 grand budget get me if I did all the assembly/disassembly? I want to pull the whole engine, crack the case and build her back up anyway so I figure why not have some fun and really build her up, I know strokers need premium but since everything now has the ethanol I will go out of my way to buy the rec 90 ( non-ethanol 90 octane) will that sufice for a stroker? I know all this will also require a new carb, but I should be fine with gravity fed fuel correct? No need for a pump.

 

Hammer Performance 1250 Kits
Hammer Performance Quote
Look at that last link, there's a few things you can take off there to save you some money since you're gonna do all the labor.

 

You have asked how big can you go, to which a simple solution is check out the websites of Hammer and NRHS, both of whom get frequent mentions in here. They are leading race tuners and builders of Sporty engines and have a wide range of options for doing what you want. We can add S&S to that list, as they also make a range of suitable products, including their SB100 engine, a scratch-built 100 cubic inches!

 

I would like at the Screaming Eagle stage 2 race kit from Boardtacker Harley also. For $1015 you get 1200 jugs & pistons, gaskets, cams, extra clutch plate & SE race tuner. Probably the route I'm gonna go when I do mine. For about $2400 you can get the stage 4 kit & my tuner said its over 100hp all day.

 

Thanks for the feedback. I'm becoming a fan on the 103" sidewinder big bore kit from s&s. Anyone have any experience with it? All the other kits only seem to expand to 1250cc

 

I believe that NHRS now has 88 cu. in. kits.

 

Here's a link to hammers 88 & 90 cubic inches

http://hammerperf.com/xlbigborekits.shtml#88cikits