| Author | Message | ||
     Richieg150 |
Have a friend that has a sporster.He is installing thunderstorm pistons and heads.His bike now has duel plugs in the heads.He is considering having the thunderstorm heads drilled for the addittional spark plug.Im telling him not to do that!Can he change the ignition or coil,so he wont need the addittional spark plug?I guess he figured for about 100$,he can have the heads drilled and tapped,Im telling him if he does that it could affect the performance of the heads!?How about some input from somebody on what he wants to do? | ||
| Buellistic |
ATT: Richieg150 Tell your friend to keep the dual plug heads.Reasons are:1)You get a better spark burn.2)The heads have a better combustion shape. The squish area is 10 to 1. The way to go is put thunderstorm/firebolt valve seats in. Use the firebolt valves & springs. This will give the engine better useable bottom end where every body rides and better throttle responce with the lighter valve train. The 1200 c/s heads have the same port shape as the single plug lighting heads. This will make the engine a torquer in the twisties. He will have to cut the valve pockets for larger valves in the stock pistons. In buelling BUELLISTIC and/or Hardley-Harley | ||
| Jssport |
We took a look at this on our Sport models (sport uses 97 S1 modified heads with dual plugs), and it appears that are two paths if you want to stick with single plugs on the TS heads. - 1 replace the entire ignition setup - 2 get a twin cam coil and a coil bracket from the std sportster. It should all bolt straight up. The Twin Cam coil and 4 plug sport coil use the same connector. (disclaimer .. this has not been attempted yet,.. please let us know the results) | ||
| Buellistic |
ATT: Jssport "i" would like for you to make a comment on my post 4Nov Mon 2:26pm!!!!!!!!!!!!!!!!!!! In buelling LaFayette,AKA BUELLISTIC and/or Hardley-Harley P.S. Blake this could be interesting?????????? | ||
| Jssport |
I thought I did ???? ""i" would like for you to make a comment on my post 4Nov Mon 2:26pm!!!!!!!!!!!!!!! " | ||
| Buellistic |
ATT: Jssport OK!,OK!, So "i" will ask you ONE guestion at a time!!!!! Why would you recomend changing coils when all you have to do is cap the extra plug wire hole rather than reenginer the coil mounting set-up???????????????????? In buelling LaFayette,AKA BUELLISTIC and/or Hardley-Harely | ||
| Timbo |
Buellistic, Until very recently I had a 1200S model that I was considering thunderstorming and I wrestled with some of these issues. "Capping" the plug hole, say at the coil. Would most likely result in coil damage/failure eventually. What happens is the coil needs to discharge the current it builds up. The coil is set up to do this through two plugs not one. Also, changing the 1200S to a single plug ignition would be more involved than on other XL models. The wiring is different and the "S" model has a system check (much like the XB's) that it goes through at key "on" to make sure everything is working properly, this would most likely need to be disabled somehow. You mentioned getting better bottom end torque and a quicker revving motor by going to the bigger Firebolt valves and springs. Maybe I'm mistaken but wouldn't going to bigger valves give you more top end and take away from the bottom? Unless leaving the ports alone creates more velocity through the port. I could see how this might work. Have you done it? Also about the lighter valves, again I may be wrong but, I don't think you are going to notice any difference in how quick the motor revs by going to lighter valves. I would agree that you should be able to rev higher with less valve float though. If you want a quicker revving motor, look to the flywheels and windage tray. Timbo | ||
| Jssport |
The sport model uses a completly different ignition system than all the other XL based models. It was the test bed for the Twin Cam ignition. We sometimes refer to it as the "orphened" ignition. There are no aftermarket replacements for any of the individual componets. HD Screaming Chicken offers 6800 + 7500 modules bundled with a higher output coil. There have been several recalls of these units, my bike sat at the dealers for 10 weeks in 98 (98 was the first year for single-fire dual plugs) as they tried to figure out why the front cyl kept dropping. The mofoco finally stepped up and replaced the entire unit with 99 spec componets after I contacted Ohio's Atty General office concerning our lemon law. The 2nd generation SE units were pulled and I had to wait unitl spring 99 until the 3rd generation units came out to get past the stock 5200 rpm limit. For 99 models and up they took the warning light off the tach, since it seemed to be causing concern amoung owners and mechanics, it would come on when there was no problems and wouldn't come on when there was one. It displayed different error codes without having to use a scanilizer. The single fire dual plug system uses a very low resistance coil (0.39 vs 4.3 ohms if I remember correctly, twin cam uses same type, just a single plug unit) as compared to std XL's. The sport model coil will blow if you just hook up one lead. The twin cam coil (single plug) will bolt up to a std XL coil bracket. It also uses the same trigger lead as the sport model. A XL list member had Wes Brown replace his ignition with a dyna 2000 (I believe) and that's the only time I've heard of it being done. I'm not sure of what Wes did to make it work, but as everything on the sport model ties back to it's proprietary black box, I'm not sure what the end result was. On your (1) specific question, I would not recommend plugging up the 2nd plug leads on the 4 plug sport coils, I believe it will blow the coil and possibly the pickup module. Anything else ?? Jim S | ||
| X1glider |
Yep, Jim and Tim are correct on the coils. The TC uses the same type and resistance. PLugging the coil will damage it. When the field collapses the votage must go somewhere. It's only 100 bucks, add the 2nd plug holes to the TS heads and make good use of the extra spark intensity. Ditto tim on the lighter flywheels for a quicker revving engine. | ||
| Bomber |
Tim/Glide downside of ligher flywheels? anything out of the ordinary (compared to, say, a small block chevy)? | ||
| Timbo |
Bomber, Less inertia, or in other words, a larger (heavier) rotating mass keeps its momentum longer. This would be seen if two otherwise similar bikes, one w/lightened flywheels one without, where traveling at the same speed and began going uphill. The stock bike would slowly begin to pull ahead, the one with lighter FW's would be forced to downshift sooner to maintain rpm's. The flip side of this is that from a dead stop the bike w/lighter FW's would get to the hill first due to a quicker revving engine. So, as with most things in racing it's a trade off between what is more important and also/or having a good balance. Timbo PS Lighter FW's are good if you like to downshift as part of your braking (compression braking) because not only will it rev quicker it will slow down faster too. | ||
| Jssport |
I've got a 98 S1 flywheel (I think it's 4lbs lighter than the stock XL) in my 98 sport with an Axtell windage tray, Wiseco forged TS pistons, stg 2.5 headwork, it revs slightly quicker, but it vibrates quite a bit more, quite a bit. The compression braking issue which Timbo (Hi Tim) mentions was cleared up by using the SE .536 lift cams. As an old 2 stroke roadracer, I hate compression braking, it makes me sloooow. | ||
| X1glider |
Lighter flywheels won't cause a problem as long as it's counterweighted properly. Heavy flywheels shine on long distance lazy cruising and smooths out the power pulses better. On a circuit track, the lighter flywhhels would allow you to acclerate harder out of a turn, but in cruising more vibration would exist. I disagree with Tim that the lighter flywheeled bike would need to be downshifted to maintain rpm. In fact I think the lighter flywheel bike would pull up the hill more easily since the combustion process has less weight to force around in a circle. The power created in the combustion chamber doesn't change because of the weight of the flywheel. The flywheel absorbs the energy and stores it. It releases that energy in 2 ways, during compressing braking, it tries to keep the engine going, under acceleration it tries to hold it back. What does your friend want? More acceleration or comfy cruising? A little of both. For reliability I'd go with stock weight. The lighter ones would surely vibrate things apart more easily. | ||
| X1glider |
Yeah, more valve overlap decrease engine braking too. Also allows you to start a high compression engine easier. On topic, dual plugs rock! | ||
| Bomber |
Friend? nah, it's me . . . . hmmmmm, sounds like, as with everything, there are trade-offs . . . . my M2 is my track bike, B'trax mount, touring rig, commuter, you get the idea . . . . have to run it through the cost/benefit routine in my head (which, happily, most always involves sitting with a piece of scotch) thanks gents . . .. I really appreciate it | ||
| Timbo |
Glider, In the example, if both bikes were similar except for the FW's, and if both bikes were going the same speed, with the same gearing and the load on the motors increased due to a hill or even a sudden headwind, the one with the heavier rotating mass would be able to maintain rpm's longer due to the stored up energy within the heavier mass. Timbo | ||
| Jssport |
Ok Tim, but what if they both were stopped at the bottom of the hill, and needed to go up it ?? | ||
| Timbo |
Ah ha, That's a different example from the first, of course the lighter FW bike would rev quicker and get the jump, not only that but the heavier FW bike would have a harder time getting up to rev because the load on the motor would be compounded by both the hill *and* the heavier mass. Timbo | ||
| Jssport |
But if both are going at the same speed approaching the hill, and you lock the trottle in it's position, the heavier bike might be ahead at first but the lighter one will eventually pass it if the incline is long enough. If the hill is steep enough to require increasing the throttle position, the lighter one will pull ahead quicker. Maybe, maybe not ?????? | ||
| X1glider |
If you keep the throttle constant as the bikes go up hill, the heavier FW will coast up a little further. But when that runs out (in a matter of a few seconds) both bikes will drop rpms. The heavier FW will lose more rpms cuz it has to work harder for a given throttle position under an equal load. Here's another twist: because of the uneven power stroke, there is 45 deg of rotation in the cycle where the engine is fighting against itself. A heavier flywheel would combat that better. Obviously a lighter flywheel would be tops in a drag race. I'd like to know if this shows up as HP in a dyno run. | ||
| Timbo |
Ok, We are back to the first example. Let's agree that if the hill is steep enough both bikes will have to downshift to keep going up. The lighter FW bike (to be known as LFW from now on) would lose rpm's first, having to downshift sooner, during this time the HFW bike would be pulling ahead but would eventually have to downshift too, but he would be able to maintain a higher gear ratio longer before he downshifts and if he is competent and doesn't loose too much engine speed he can carry the lower gear longer than LFW can too thus increasing his lead but with diminishing returns for distance traveled, losing his stored energy until eventually the table is turned and LFW bike begins to see gains. The questions being, will the gains LFW bike eventually sees be enough to make up the distance HFW bike has gained? Like you said, maybe, maybe not. Lots of variables such as what is the difference in FW weights? What is the rate of the incline? What is the length of the incline? Who has cooler graphics? which guy gets more chicks? How many...?  I think we are getting off topic, what about you? Timbo | ||
| Bomber |
yikes! that'll teach me to go to lunch ;-} thanks for the food for thought, gents | ||
| X1glider |
Why bring downshifting into it? I let my bike run from 1800-6500 rpm in any given gear going over hilly terrain, out of laziness no less. Lets say that we don't downshift. Sure the LFW bike would slow down first over an extremely insignificant distance, but it would be able to maintain rpms easier. You make it sound as if the HFW will carry the bike over a large distance, it won't. Don't forget that there is combustion going on at the same time. An equal combustion will be able to turn a lighter flywheel easier. So maybe the LFW won't be effected at all. | ||
| Josh |
Yes but what about the contact patch?  | ||
| X1glider |
Josh,  , don't ever bring that up again! | ||
| Csg_Inc |
So if they maintain the exact same RPM then the guy in front will remain in front. Must be why Trials bikes are so much fun. Big Heavy Flywheels | ||
| Vr1203 |
I have a big bog off the line ,after I drop the clutch @5000rpm ,the turbo bike pulls the wheel then just goes flat. Turbo lag I suppose. Would a heavier FW get me through that flat spot? | ||
| Jssport |
Here's a good question, and Elfe related : While we all know that a lighter flywheel gives better acceleration, does a heavier flywheel give more top speed ??? Aaron says no, several of the ancients say yes. what sayeth you ?? | ||
| X1glider |
I say no. The heavier flywheel absorbs some usable power. Might be the difference between 199.999 and 200 mph. | ||
| Timbo |
Jim, The benefit of a heavier FW is the motor works *less* hard to keep the the same rpm under an increased amount of load. The rate at which the benifit diminishes depends on the weight of the FW and how much additional load is placed. As far as LSR applications are concerned, it would be interesting to experiment with. With HEAVY FW's and enough run-up space if your gear ratios were close together (to keep the rpm's from dropping out of their optimum range), and enough gears you could carry a greater load (the load being, higher speed=greater resistance=greater load) with the same amount of HP. Remember, I said *experiment* with, because it would probably come down to timing, distance and amount of FW mass to find the *sweet* spot where the HP was just enough to push the vehicle at it's fastest during the timed mile. Remember you are using the stored energy in the flywheels to help the motor push the highest gear at the greatest resistance. At it's optimum you would enter the mile slightly faster than you would exit because if the HP was at it's max ability to push a given load you would be using the energy stored in the spinning flywheels to help hold the rpm's up through the spot you wanted. Does that make sense? Timbo |
