| Author | Message | ||
     Bhillberg |
As stated in other posts, I am new to all of this. I was just looking through the board here though and noticed talk about nrhs 1250 kits. I went on their website and they claim 124 rwhp with a bolt on kit that costs $780. How much other work must be done if you get this kit and are the numbers accurate? I know from dealing with cars that sometimes the numbers are too good to be true | ||
| Natexlh1000 |
50cc aren't getting you 40hp without lots of other stuff! | ||
| Scott_in_nh |
Yep and all the other stuff without the extra 47cc will get you about 36hp! | ||
| Bhillberg |
fair enough, then why in the hell are so many people so intent on these kits? | ||
| Kyrocket |
Well for me it was all in the timing. I had to pull the cylinders this winter for a base gasket change anyway, my oil pump drive gear went south on Sept. 5th and I ran across a good deal on some 1250 cylinders so why not. So if I ever get around to head work I'll already have some other stuff done. But I agree, the money would probably be better spent on good head work but like I stated, it was all in the timing. That and I wanted to do some other things for a while now like the XB rocker boxes, black push rod tubes and a few other aesthetic goodies. I think that 124 rwhp is on their shop mule M2 if I remember correctly and it's got more than just cylinders and pistons. | ||
| Phelan |
The web site isn't saying that's the 'only' thing they put on to get 124hp. 1250cc as stated above is all about timing. If you blow a piston, chances are you don't wanna split the cases and bore them for an 88"(1430cc), but if you have to replace the cyls and pistons anyways, 1250 is as big as you can go without boring the cases. That should be explanation enough of why people get it- the biggest available on the budget. 1250cc kits generally runs 5% more power than their forged 1200cc counterparts. That said, the forged piston in the 1250 will perform SIGNIFICANTLY better than the cast 1200cc variations. IMHO, 1250cc is best suited as a compliment to other simultanious upgrades like headwork, squish bands, cams, carb, etc. (Message edited by phelan on November 06, 2008) | ||
| Bhillberg |
may be a stupid question but just to make sure, forged pistons are NOT stock correct? | ||
| Bartimus |
Yup, the headwork, and the cams also help you make that horsepower. I've got a 1250 kit in my '95 S2 that is making 104 rwhp that has been dependable as hell for 14,000 miles now. I think the dyno sheet for it, is on the NRHS site. You can't go wrong | ||
| Phelan |
correct bhillberg, stock pistons are cast, and are a heavier and weaker than forged pistons, not to mention the forged ones look a lot purtier new  . Depending on where you get them, stock pistons run $50/ea from da factory and forged pistons of most all variations and brands are $150-200/ea. You get what you pay for. | ||
| Xldevil |
Not to forget that the 1250cc pistons are said to unshroud the valves,means better flow-better go. That would likely give a good headwork the last kick. Ralph | ||
| Alex |
Thatīs just a fairy-tale. | ||
| Chasespeed |
Plus, the small, but, there, compression bump... All things considered, the 1250, some nice cams, 536s, or 575s, and some headwork, will make for a FUN bike... Chase (Message edited by chasespeed on November 07, 2008) | ||
| Preybird1 |
Yes you need the heads worked to get the full hp. But the iron lined jugs are far superior and cool down a lot faster, Also this is a nice upgrade to the bike. Check me out in the summer next year i will have the kit done to my bike and so will kyrocket sounds like. So we will have a better idea of what we are really getting for the money, Hhhmm cams are gonna really help, which ones.....Is the ticket. I am not sure just yet but i was toying with the idea of changing the crank to an s and s and going to the 88" stacks. i will buy a new xb12s for going to work and just riding around! | ||
| Buellistic |
BIG PISTONS, HOT CAMS, BIG VALVES, BIG CARB., and LOOOONG STROOOOKE, "LET THE FUN BEGIN" !!! | ||
| Torqd |
Well Aarons 1250 was kinda the king of 1250's. When you own the shop that made the combo you can put umteen hundred hours into fine detail and tuning. If you look at their other 1250 motors you will see an average of around 100-105hp... not 125. Shoot even their average 88in are around 115hp. Not that they can't make more... it is all in the money you spend. My 88" made 130 plus and has not been dyno'd since bigger cams and more compression.(heads by former NRHS employee many years ago) The last few HP are the expensive ones:-) Good Luck in your journey! | ||
| Scott_in_nh |
It is true that a larger bore does unshroud the valve because there is more room between the open valve and the cylinder wall. How much that helps in this application I am sure is documented somewhere, but I do not know it. Now i have a comment/question about what some of you have posted about forged pistons. My understanding has always been that forged pistons are heavier because of the forging process limits the complexity and shape of the forging itself compared to cast pistons which can be very complex in their design. I have also always understood that forged pistons needed more piston to wall clearance and therefore had more blowby. In addition, hypereutectic cast pistons run the tightest clearances and are lighter than forged making them better (more powerful) than forged. The only advantage I am aware of for forged pistons is their strength for highly modified engines. Where am I wrong? http://webpages.charter.net/beckracing/page11.htm | ||
| Jos51700 |
I've never understood the allure of a 1250 kit, myself. It is an opportunity to get some better pistons, but it's little more than that. Now, a 90-inch kit..... Stock pistons are, I believe, a hypereutectic piston, but I may be wrong. Forged pistons don't have more blowby once they're warmed up, because the running clearance is the same. They do tend to burn oil when cold, and rattle like crazy. Forged pistons are usually lighter, because the strength increase requires significantly less material. Overboring does unshroud the valves, but without headwork, it's a minimal gain. | ||
| Preybird1 |
90" Will it fit in the frame? of the x1 i mean! Finally i will have the head finished today and will install sunday if i can pull myself outta bed! | ||
| Chasespeed |
Yes, a 90 inch kit will fit just fine... Chase | ||
| Phelan |
the only problem with the 90" kits compared to the 88" kits is that the cylinder walls become very thin and therefore should be made of a stronger material, which is why NRHS only sells their 90" kits with cast iron Cylinders. Let me tell ya, cast iron weighs a LOT more than the aluminum cyls. | ||
| Scott_in_nh |
Forged pistons are usually lighter This is different from what I have been taught and what I have read - including the link I posted above. Can anybody confirm the weight of the stock piston and a forged piston? |
