883 to 1200 conversion (parts and kits)

[jmattsen]

since you allready bumped the thread il throw in my question also.

would going from a 1200 to a 1250 be possible by boring my cylinders out like the 883 to 1200?

and did we decide it would even be worth it cost wise?

[Dragstews]

since you allready bumped the thread il throw in my question also.

would going from a 1200 to a 1250 be possible by boring my cylinders out like the 883 to 1200?

and did we decide it would even be worth it cost wise?

To give y'all an idea of how much meat is bored out of a 883 jug are these photos...



The 883 jugs has a standard bore of 3"



Taking them to 3-1/2" which is the standard bore of the 1200cc




At the 1200cc bore the liner gets pretty thin... Three more bores can be done to them at .010 a wack .... Alot of manufacturers makes a .040 over... With that bore the liner turns into an eggshell.....



This pile of cutting is 1/2" of meat out of each jug....
Just went from 55 cubic inch to 74 cubes... By bore alone.

Want more....???
Could build it into a stoker....
That would require longer rods and taller jugs...

Have done a few larger bores and keeping the short rods in play..... This will take the cubes to 84 inches.
Requires boring the cases for 3-5/8" Big Bore jugs, then bore out the jugs to 3-3/4"
This is a one time shot being "NO" oversize pistons are offered...

[docmel]

Been there, done that. Frankly, just going with a bigger bore from 883 - 1200, you will not see much of a power increase. To get a power increase, you need to add a slightly hotter cam (nothing crazy needed), another carb other than OEM, with some good head flow work to take advantage of the bigger bore. Otherwise, you wont get a power increase that was worth the cost of just going with a bigger bore

[Dragstews]

The 883cc heads won't make much power being the chamber design is a problem ..
They have a raise chamber, meaning the valve stems are longer.
Super small valve heads, seats and ports.... Just don't cut it...
Mega rework to get them up to snuff...

Next step up to feed these new numbers in cubes would be 1200cc heads and flat-top pistons...

Up from that would be a set of Buell Thunderheads and matching pistons....
Now were'll taking horsepower.... Nice set of cams, carb and pipes would be icing on the cake..

[guiltyview]

when i get cylinders bored, i take the pistons to the machine shop so there's no guessing in their machine work.

it's def more affordable if you do the leg work yourself. i, personally, wouldn't bore an air cooled motor on the tight side. pistons swell faster than the cylinder walls expand.

different material piston vs different material cylinders vs different material liners all require different fitment. there is no set in stone method. some like it tight some don't

[Dougtheinternetannoyance123]

Please DO NOT part out any Buells for your Sportster project, that being said, there are a ton of articles on the web on doing these convesions.
Or buy the Sportster perf. handbook (although the newest version is spendy) read up on stage tuning 1,2,3, 4 and relative costs vs benefits.
I disagree with the other poster about it not being effective. After you completed stage 1 (Air cleaner, carb tune and exhaust,,,,NOTE Use CV Performance see their website) then Stage 2 is 883 to 1200cc,, and for the dollars is a very good investment. Yes,,, buying the kit makes sense. And Lowbrow are good people (ive known Tyler since he started in his garage, say Hi to Todd as well) well worth spending your pesos there.
I would recomend 1200 heads,,, or send in your heads to NRHS and have a basic clean up and rework. Both Hammer Perf and NRHS are good. (Some issues over the years but been addressed)
YES,, you CAN buy a big bore kit that will fit in cases,,, but thats overkill for most and too big requires case machining. Read up on NRHS and Hammer performance and their tech pages. Google various topics. Some good write ups out there or buy the Sporty perf book as well.
Of course CAMs are a big help, a big bore alone WILL produce a measurable diff. but its the TOTAL package and it can be done affordably. But power isnt cheap and once you start that road,,,,,,,, it can add up. Do your research first. best investment you can make. I own a bunch of Sportys and Buells, including a 1450cc hot rodded monster. (Axtell cyls, The whole menu of NRHS goodies, RedShift cams, blah blah blah,,, 140hp and 112 ftlbs torque if you believe the dyno sheets.)