883>1200 vs's NRHS 1250 upgrade kit

I have an 883, and when it comes time to rebuild the top end, I figure on going up in size. I've heard different numbers for HP levels for the 1200 kits. Someone said 65, and someone else said mid 50s. I'm not looking to get giant increases in HP or torque, but I'd like to find out what the NRHS 1250 kit puts out, as well as the 1200 kits. The 1250 kit comes with 10:1 or so pistons and I'm wondering if that will shorten the life span of the engine.
Any input would be very much appreciated.
Thanks, David.

The NRHS 1250 kit is probably the "best bang for the buck" on the market now & I've been to that shop & I know the quality of work that comes out of it. Not a major HP improvement over a typical 1200 conversion, but as big as you can go without boring the cases & what you'll get from them that you don't from most everyone else are parts that are matched to each other. The biggest conversion problem of all is using off-the-shelf cylinders & pistons that weren't precisely measured & machined to match perfectly, but NRHS knows how to do that & they do. They've always been good @ answering questions before a purchase too, so you get what you want the 1st time.

As to HP/torque, you should be in the low to mid '70's on both. You didn't say what year model your bike is & the heads/cams will affect that, but still, 72-75 HP & torque is realistic with the basic conversion done properly. I would not go over 10:1 compression unless you're planning on having head work done too & premium gasoline is always available. Besides, contrary to popular belief, increasing the CR does not of & by itself increase power - it's just one of several factors. Cylinder pressure makes power & you can increase that while doing nothing to the CR.

thanks guys, those answers help a lot. The other thing I forgot to ask is, is it possible to use the 883 heads, and if so, how much of a difference would those be power wise to changing over to some 1200 heads? It's a 1997 xl.

Yep, it's possible to use the stock '97 model 883 heads & the basic kit will do that. The difference between those & 1200 heads is combustion chamber & valve size - larger on both with the 1200, but the combustion chamber design ain't all that great & you can actually get more power working with 883 heads.

The smaller valves & combustion chambers in 883 heads make for better low-end torque & strong mid-range, but the larger valves of the 1200 heads will give more top-end HP. Up thru 2003 models, the cams were the same 883 & 1200 (except the rare 1200S) & those cams work better with 883 heads, so if stoplight-to-stoplight power & torque on twisty backroads which means you don't shift gears as often is more important than blazing down the interstate, the 883 heads are better.

And if you want the larger valves, long before I bought a set of 1200 heads that need work anyway, I'd send NRHS the 883 heads & let them do their magic on 'em. Keep in mind that different heads will require different pistons to keep the compression ratio in a streetable range, but if they know beforehand what you're going with, you'll get the right pistons for the application. For what you want to accomplish, I would think the stock heads with some clean-up work would do fine - give you about 50% more power than you've got now without any concern about the engine wearing out too fast.

You can get more power, but there's always a trade-off - for example, I've got a set of 883 heads worked to be Buell Thunderstorm heads with domed pistons to match, larger valves & a set of cams matched to the 883>1200 application - makes 95 HP @ the rear wheel. Side-by-side on the interstate in a "roll-on contest", a 1250 with 883 heads wouldn't have a prayer, but stoplight-to-stoplight, the 1250 would win every time.

I always say think "system" rather than individual parts - consider how, when & where you ride & what you want your bike to do. The NRHS guys are primarily Buell guys who like higher rpms, but they're just as good @ building a Sportster for someone who doesn't go to the Bonneville Salt Flats like they do, so go for what you want to accomplish.

One thing I should add is that the ONLY difference between an 883 & a 1200 engine on your Sportster & nearly all others '91-'03 (except external appearance, black cylinders vs. bare aluminum, etc.) is the cylinder bore/pistons & the combustion chamber/valve size. The flywheels, rods, bearings, cams, pushrods, rocker arms, rocker boxes, transmission gearing, etc. is the same & all parts are interchangeable. That's why an 883>1200 conversion is so easy - you don't need to tear into the bottom end, re-balance the flywheels, buy new cams, etc. - it's nearly all "bolt-on".

The 883 has a 3" cylinder bore, smaller combustion chambers & valves in the heads - the 1200 has a 3.5" cylinder bore, but the same bottom end, cams, etc. Stock 883 cylinders can be bored out to 1200 size, so you don't even have to buy new cylinders. 1200 heads will bolt on an 883 & vice-versa. But the piston top & combustion chamber MUST match or you will have major problems. You can put 1200 size valves in 883 heads too, but the stem length is .600" different, so you can't just slap in 1200 valves. But 1200 conversion valves are readily available.

What I'm getting at is that 883's & 1200's are NOT 2 different engines & a lot of parts someone may want to sell you don't actually need. Yes, there are some other differences such as an 883 comes with a 27-tooth front belt sprocket, a 1200 comes with a 29, but those are interchangeable too & you don't need to buy a new belt. The change will throw your speedometer off a bit, but there's a fix for that too - change the speed sensor.

There are a lot more differences as of the 2004 models & buying an 883 with the intent of making it a 1200 later isn't as good a $$$ deal as it used to be, but for your '97 model, you'll end up spending a lot less making the conversion than if you'd have bought a 1200 to begin with. NRHS gets the extra 50 cc's with custom-made cylinders with slightly larger bore, but everything else is still the same & with respect to putting the engine back together, making that conversion is the same as an 883>1200 conversion.

Wow, Thanks for all that info. You made up my mind; 1250 kit with the 883 stock heads for more torque. I got the high speed stuff out of my system a while back with the rice burners. Great, thankyou.