| Author | Message | ||
     Lakes |
Hi all , just thinking about my new year planed upgrade & forever set up. Well first off i know bolt pattern is different XL to XB. Just as i have Billit engine mount. Is it possible to change bolt pattern on an XL mount to allow it to mount to XB? Thank's. | ||
| S1owner |
I dont think so but Phelan is the expert on that. | ||
| Lakes |
Thanks hope he can answer, other wise can weld chamber on thundsrstorm to run flat tops . Buying Axtell cast iron88" barrels just want to use stock valve size's, could get stock XB heads, but if not worth trying to make XL billit mount fit XB. Will weld up thunderstorm chambers so can run flat tops think will use beehive springs N6 cams . As i have them in now. Will use stock clutch just grenade plate removed . Can machine cases at my friends. Also rebuilding gearbox friend very good with HD race prepared gear box has just on 40 years experience at it. Plan is to make it a fun street bike that i can also bracket race, for fun. Don't know what bottom end will be till i pull stock flywheels out and look at them, have a set of sportster Corrilo rods i can use . I have the rest of the bike set up & it handles well i ride it regular. So i know it well just bit more grunt but like the n6 i have in now. Will see what trap speeds it does if 135mph quarter mile will be happy. As will know it has the power i want. | ||
| Lornce |
Is there any difficulty fitting XB guides, valves and beehive valve springs to XL Thunderstorm heads? Do XL rockers work with the XB valves and springs? Any and all info appreciated. | ||
| Phelan |
Welding Thunderstorms into bathtubs is a lot of welding and risks moving or dislodging the valve seats, I would recommend against it. You can modify just the bolt hole on the pushrod side of the billet mount to fit XB heads with some work. It needs to be ~3/8" inboard. I would weld up around the boss and mill it to match the flats, to reinforce the hole, but it may be fine without it. The rev2 billet mount NRHS used to sell, before it was discontinued, had a walleye hole to fit either model of heads. As far as using the XB hardware in Tstorm heads, it is possible, but not the biggest advantage. The ports in the XB heads flow about the same as the Tstorms, but they are smaller, so they make more power due to better velocity. It is true that the beehives are lighter, and avoid float to higher RPM with the 7mm valves than the hardware in the Thunderstorm heads, which is stock in all 84-00 Evo heads, 86-03 Sportster heads, and 99-04 Twin Cam heads. The beehive springs in the later model heads handle up to .560 lift and are found in 03-10 XB, 04-up Sportster, and 05-up Twin Cam. | ||
| Lakes |
Thanks for that Ross! I have had stock HD chambers & ports welded before no problems, but will check with welder he does aircraft welding & machining. Yes I like small ports stock size valves myself if I use XB heads I will leave ports stock just going to axtell Cast iron 3 13/16" bore will use the n6 cam's I have now but there is a nice red shift street cam think 570? Lift I would use if n6 don't work well with combination. Thanks for info on the billit mount Ross & merry xmas the D&D pipes you sent work great!! | ||
| Lornce |
"As far as using the XB hardware in Tstorm heads, it is possible, but not the biggest advantage. The ports in the XB heads flow about the same as the Tstorms, but they are smaller, so they make more power due to better velocity. It is true that the beehives are lighter, and avoid float to higher RPM with the 7mm valves than the hardware in the Thunderstorm heads, which is stock in all 84-00 Evo heads, 86-03 Sportster heads, and 99-04 Twin Cam heads. The beehive springs in the later model heads handle up to .560 lift and are found in 03-10 XB, 04-up Sportster, and 05-up Twin Cam." I've got a set of '98-style Thunderstorm heads that could use a freshening up and figured while I was in there I might as well go to the 7mm stem XB valves and beehive springs. My only concern is if the XL style rockers will work with the smaller valve stems? Looking at dyno results from the XL and XB type T-Storm motors, the XL-type create higher torque and similar peak HP at 6k rather than 7k rpm. That leads me to surmise the XL-type heads have more efficient combustion chambers. They certainly feel stouter in the midrange. Anyhow, I'm happy to stick with those heads in my tubers, but if I can benefit from lighter valves/springs that's good, too. | ||
| Phelan |
The 04-up XL1200 heads are exactly the same castings as the XB heads, just machined for side breathing. The reason the Sportsters peak early is because the low overlap cams used in them create significantly more cranking pressure, and thus more torque. XB12 runs about 150 psi cranking pressure, whereas a new 1200 Sportster runs over 200 psi. The Sportster can do that because the motor is more open and runs cooler than the XB, as the heat in the XB would cause detonation. The rocker arm geometry is unchanged from 1991-2017. 7mm stems or 5/16" stems makes no difference. (Message edited by phelan on December 16, 2016) (Message edited by phelan on December 16, 2016) | ||
| Lornce |
Yeah, I'm not talking about Sportsters, I'm talking about Tube-frame Thunderstorm motors vs. XB motors. The Tube-frame motors are stouter in the midrange while XB's spin 1k rpm higher to make similar peak power. Cam timing and combustion chamber efficiencies both influence the result, which is higher torque earlier in the rev range from the Tube-frame T-Storm motor. Looking at the pistons and heads I'll hazard to guess XB pieces were more cost effective to manufacture. Anyhow, thanks for the info re. the rockers: That's what I needed to know.  | ||
| Phelan |
The Tubers have similarly high cranking pressure (usually in the 180s or more) due to lower lift, low overlap cams, and thus the same applies. The XB heads are a much more efficient design with much tighter, larger squish band, and significantly lighter pistons and wristpins. The XB12s rely on active muffler control to have very good bottom end, because they have significantly less cranking pressure due to the more agressive cams. It was a trade off made so that the motor could be similarly poweful and efficient while not overheating in the XB platform. If you were to deck the XB heads enough to increase cranking pressure to similar levels, it would leave a tuber in the dust, but suffer from excessive heat due to the frame wrapping the motor. The XB top end is a better design in every way than the Thunderstorm setup. (Message edited by phelan on December 16, 2016) | ||
| Phelan |
Cranking pressure is your dynamic compression, and thus is a huge factor in power output. The difference between 150 and 200 is 20%, and 150 to 180 over 18%. 20% more cranking pressure can often add 10 ft/lbs or more, and thus is a huge factor to consider. | ||
| Phelan |
If you put an XB12 top end and .551 cams (either SE E grinds or re-timed and cut XB cams like I offer) in a tuber, you will net similar 150ish psi cranking pressure. That is why the torque is down. To enjoy the better flow of the XB heads at higher RPM while not losing bottom end or midrange, you need to increase the cranking pressure to be similar to the tubers, either by aftermarket pistons or XB9 pistons with the domes shaved down, or significantly decking the heads and using appropriately sized pushrods. Point is the .551 cams need smaller chambers than the the .497 cams to net 180-200 psi cranking pressure. If you do this, the XB setup on a tuber will leave a stock tuber in the dust, with at least 10 more HP, using esssentially stock XB heads. The tuber motor is not shrouded in heat the way an XB motor is, so it can handle the cranking pressure much better than the XB. (Message edited by phelan on December 16, 2016) | ||
| Phelan |
This is also why cams alone do not make the great performance increases most people are looking for. The motor needs to built around the cam choice to utilize the most performance out of the cams, or the cams need to be carefully chosen according to the parameters of the motor. | ||
| Knuckleduster271 |
How much should one mill a set of xb9 pistons to be fitted into a tuber? | ||
| Lornce |
Good intel. Thanks Phelan. | ||
| Phelan |
James, I cut .050-.060". Lakes, back to your situation. Another reason to use the XB heads is that N6 cams are a big compromise, and originally designed with early opening, late closing specifically to work within the constraints of the 03-under HD springs, which are only good to .500" lift. By using the XB heads, which are overall much better, and have better springs for cams that will work much better, especially with the big bore. With stock XB heads and flat top pistons in the big bore, I would go with at least an E grind cam, like the re-marked XB cams I use, or something like an NRHS CAT3, SE 536, or Hammer 560 cam, as all will have good overlap and lift to maintain powerband to 6000 RPM while still maintaining 180-210 PSI cranking pressure, due to the increase in motor size, while still using the stock XB 62cc chamber. It certainly won't be the most powerful, but it will excellent bottom end and midrange, and longevity similar to a stock motor, with the exception of ring seal over time. (Message edited by phelan on December 16, 2016) | ||
| Lakes |
Thanks Ross, only used the n6 in first place trying to lower cranking pressure as was up too high with n4 cams but just the n6 cam change nothing else made cranking pressure go up not down, last i checked it was 230pound . I used dyna p ignition to set a less agressive advance than the lightning modem my bike had starts quick and easy runs fine i keep rev's up over 3,000 | ||
| Phelan |
It went up because the intake is open longer pulling in more air. | ||
| Lornce |
For clarification: You're saying Buell went with the lift and duration of .551" cams in the XB motors to keep cranking pressures down while still producing enough flow for good power at peak revs? I was of the understanding that a good and effective squish band and combustion chamber would create turbulence to accelerate efficient combustion (ie: rapid flame propagation and gas expansion) which increased combustion pressures therefore torque. One measure of combustion efficiency is ignition advance required for maximum power. ie: Less required advance indicates greater combustion efficiency. However... nitric oxides tend to increase with combustion efficiencies, and nitric oxides are bad, baad, bad... Which lead to spinning less efficient motors higher to achieve power targets in spite of the torque deficit incurred to keep the EPA from shutting you down over nitric oxide emissions. Hence XB heads and .551 cams. No? | ||
| Phelan |
You're making this more complicated than it is. .551 cams were chosen because the 9 motor was the main target product, and it needed bigger cams than .497s to make power at the higher target RPMs, because Buell wanted a higher revving motor, particularly for ease of modulating power, since it was originally meant to be turbocharged. The 12s got the same cams by default, for many reasons already discussed. Reving the motor out to higher RPM is generally more enjoyable for people as well and was a big desire in development, hence why the 08 XB12 motors got a raised rev limiter compared to the 04-07 models (7200 rpm vs 6700 rpm). XB heads have larger [flat] squish bands than Thunderstorm heads have with Tstorm pistons, and the XB setup stock runs .040-.045" squish clearance compared to the Tstorm setup that runs .070-.085" clearance. So the XB setup outperforms in that respect as well. Putting 7mm hardware in XB heads with stock Tstorm (.497) cams will net exactly 0 HP. that is my main point. (Message edited by phelan on December 17, 2016) | ||
| Phelan |
Also the XB rotating mass (crank and pistons particularly) is much lighter than the Tuber variants, and revs up a lot faster, and the bikes are much smoother, so the extra RPMs are not noticed the way they are on tubers, and are much more desired, because they are so smooth that you will quickly bounce off the rev limiter thinking you have more RPM than you do. (Message edited by phelan on December 17, 2016) | ||
| Lornce |
1. It might be more complicated than you realise. 2. No one's adding XB hardware to increase output. The heads are due for refurbishment. Good time to take advantage of lighter pieces, reduce internal stresses, increase valve guide life etc. 3. XB motors "feel" smoother primarily because of a superior isolating system. Thanks for your time. | ||
| Phelan |
I never attributed the smoother feel to the motor components, I simply said that because the motor is smoother (much to do with the isolator system, yes), and the motor revs up quicker, the extra RPM is welcome. You can add XB hardware if you want, and it will have less spring pressure and better longevity that the stock hardware. I have even done this on heads in the past, but only because I had tools and parts on hand to do it for free. But unless you are doing other work, I personally see it as a waste, especially since you imply no desire to run past 6000 RPM. (Message edited by phelan on December 17, 2016) | ||
| S1owner |
Smooth I think BMW or yami. If I wanted smooth it would not say Buell or HD |
