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About harrperf

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  1. Since I'm absolutely pissed I'll reply I received a call at 5:40 am the other day from dave. I find this whole unaccepable of which I didn't answer. this was followed by a call at 7 am of which I did answer and told dave I would send tracking. Tracking was then sent the same day. I broke my windows 7 computer beyond repair recently and with it my ktm software. This is no longer available despite the fact I own the user setting tool.... I'm told due to EPA concerns (of which harley was fined massive dollars if you recall) ktm is no longer offering the UST. in order to ensure daves ecu was properly set up I had a friend in the business who I help when I can and who helps me when he can install my map file for me at his retail pricing. I was sent tracking of shipment of the ecu and sent that tracking to dave. while I truly wish I could improve anything the us government decided to do... I can't. until the postal service provides further update, both dave and myself are out of luck with the ecu tracking. I am currently part of a wedding this weekend for a best friend , which i may point out is the WEEKEND... and I feel it's entirely ridiculous to call me at 9:30 pm any day of the week let alone a weekend day. Your time could be better spent calling the usps and getting better info, maybe they can help you on their weekend time. Until usps reports back, I am in the same boat as you. It has been paid for and dropped off in the hands of americas finest post service members. Hopefully it's a computer issue or human error and it shows up sooner rather than later.
  2. Hey,

    So I would like to get a 2017 ktm 350 exc and would like to give it maximum torque.  Based on your posts I think the best option is the SXF header with the 4.1 slip on.  Of course I would remove all the smog shit, open up the airbox, and adjust the tps.  What are your thoughts?  Your messages are not working.

    1. harrperf


      I prefer the bills slip on a good bit.
      The rest might work out ok, but adjusting the TPS is a half ass attempt to richen the bike..a remap or a proper ECU would do wonders.

    2. skylerj


      I can definitely get a remap done. What header/slip on combo will give me the most bottom end in conjunction with proper mapping?  

    3. harrperf


      You wont get much with a pipe...it's just a sad fact.  I like the bills RE13 slip on - we have worked with them quite a bit and have a stepped core technology that really improves the "bark" and snap of the bike.

      The stock header provides the best power on the dyno - bottom to top.  The fmf looses quite a bit of bottom - and peak...a lose lose.

      You may consider a throttle body mod we sell - it's an improved air flow wing design - but a restrictor insert that increases velocity. Gains are great...but usually again requires some mapping to be perfect - although I have had it run well without mapping.

  3. I don't want to go too far into detail - but power instability is an unfortunate side effect of two strokes. Cyclical variation occurs between power strokes for a host of reasons - largely due to the fact the entire engine is resonating (from pipe to cases to inlet). It's also why I have stated fuel injection is a massive challenge on a two stroke (in pure performance applications). In addition - at part throttle the engine is far from "optimum" design. The inlet tract, reeds, case volume, port tunnel sizes, port areas, and exhaust system are all design mostly around WOT power - and not 1/8-1/4 throttle power. Trials engines are quite the opposite - designed for both a torque curve that is very flat - and that peaks early - as well as low throttle opening power. these engine has very tight cases, really low exhaust ports - and mild pipe designs. you Can jet areas so rich this doesn't become as noticeable something very common on stock KTMS...but then of course you are jetted rich. my engine simulation software shows this very clearly - with a SET AFR RATIO. AKA perfect carburation - there is still large variance in power per cycle in various throttle positions. At wide open power - its hard to notice a 1hp variation out of 45. but at part throttle - when you are asking the engine for 3-5 hp - .5-1 hp varation is easily noticed - and not a by product of fuel delivery - but rather power variation (which i real world means RPM variation)
  4. Society is getting dumber. Suspension is proof of this
  5. This isn't meant to be mean....please understand I really mean this in the nicest way possible. But lack of understanding is pervasive in this sport. Air is 78 percent nitrogen. 20 percent oxygen. It leaves 2 percent for other elements - lets call those insignificant (although next in line is argon at 1 percent - also inert and also a capable of usage in a shock or fork) You will not find statistically significant data that suggest oxygen expands significantly more to temperature than nitrogen ANYWHERE. it's just a fact of science. Expansion rate to temperature is well defined by the ideal gas law - for a set volume (what forks or shocks have) the pressure rise is Pressure = (nRTemperature)/Volume R is a constant for all gasses in this equation N is the number of "moles" captured in the set volume - the molar mass per set volume and pressure of nitrogen and oxygen is quite similar T is absolute temperature from true 0. If you bother to go through the equation - you will find that the pressure rise vs temperature of nitrogen vs air is nearly identical. http://www.barrystiretech.com/nitrogeninflation.html They did the math for you in above link. That said - highly humid air will be worse than totally dry air. But even still - it's a really small amount of difference between the most humid air possible and dry air. At 95F - about the limit many people ride at and fill their forks at trackside - it's about 3 percent maximum weight of water vs total weight of air...and that 3 percent in your fork will not reach a temperature high enough to cause massive issue. In the shock - it's more critical to be moisture free. I'm an advocate for practical improvement. N2 isn't the answer. On the normal aer fork - the balance chamber and the main high pressure chamber exchange pressure every extension. This means pressure rise is equal. Seems your works version has a massive flaw as it's building truly huge pressure. Maybe your better solution would be to start the moto off with air that is already at 100F - or closer to outside temperatures if you are filling it the night before or early AM with cool air.
  6. Nitrogen provides no improvement in pressure rise if the air you use is moisture free. And even with moisture the difference isn't huge. Nitrogn IS inert which provides benefits with oil oxidation and rust prevention...but that's about it. it blows my mind people continue this non sense... it's not hard to understand with basic research.
  7. I must not understand this cone valve air fork. I'd imagine the increase in balance chamber pressure would make it substantially softer. We must have a terminology mix up.
  8. I can't read what you have written in a manner that makes sense to me. If you are saying a single stroke compression of the fork adds .5psi every time...then: Temperature rise due to compression is followed by the same loss in extension. the only net positive heat addition and thus pressure rise is from frictional heat and damping heat (not generated in the air side of wp or Showa) In our testing I generally see less than 5 psi change in the inner chamber for the length of rides most motocrossers ride. This still provides an equal rise in psi to the balance chamber on the stock aer fork. The first 4 inches of stroke are hardly different with this change in pressure. on a std fork 1 psi in the outer chamber is a more significant change in the first 4 inches of stroke. I see easily 3 psi rise in std spring forks. No one bitched about pressure rise as their fork issues on spring forks... but it's an issue all the same. my point is very simple. air forks are disliked for whatever reason..but I think that reason is NOT pressure rise issues. increased static friction is a big issue that can be easily felt on tac forks, the stock air piston is incredibly sticky. inconsistent air spring rate due to ideal gas laws vs Adiabatic gas laws is what I personally feel is the largest negative to an air spring. It is a softer rate on slow compressions because the heat generated in compression is dissapaited where a fast compression doesn't allow as much time for the same amount of heat dissapation. decreased front end weight drastically alters the feeling of stability as well as the weight bias of the bike. I have tested back and forth between spring and air on the kawi. I can attest that it's a drastically different feeling in weight on the front tire and stability to small bump strikes. headshake is a function of mass in the front end too, changing this mass alters the frequency of which it occurs. For some people the lighter front end may be more unstable at the speed they experience issues.
  9. People don't like air for a host of reasons, however can someone please tell me why a spring fork doesn't under go a more statistically significant change in spring rate due to pressure rise than an air fork. A spring fork has air in side it - if you are on the ball before your rides it starts at local atmospheric pressure - around 14 psi. Over the course of a moto - it will build pressure - easily proven by anyone here riding a moto - and checking your bleed screw immediately post moto. Generally over a short 5 lap ride you will see more than 1psi rise. However let's say you only experience 1psi. That's a 8-9 percent change from "14" to "15". In an air fork - using the ktm aer - you might experience 2-3 psi - out of 140. a change of less than 2 percent. Couple this with the fact that your air fork uses a negative air balance chamber - that ALSO experiences the same rise in pressure - the top of your stroke actually remains very similarly sprung even across 5-7 psi changes. In a spring fork there is no negative air chamber - so your pressure rise most noticeably effects the beginning of the stroke in similar effect more spring preload would have - as the actual air spring influence of 1psi is small on a system with a large air volume for the total spring rate. I personally believe all the talk of pressure rise is garbage. Spring forks do it as well. The more relevant difference on a spring fork vs air fork is the spring rate on an air system isn't the same at varied velocities. Fast hits have a larger spring rate and slower hits have a lesser rate read on that page about adiabatic vs ideal gas law. So in reality I think air forks only massive detriment is the fact they are not a set spring rate at any time. Depending on velocity and stroke usage - you get a fork that behaves differently than a spring fork. The positives in decreased weight - easier set up for a wider range of riders - and lower cost are things most people should like but do not. I like my personal bikes SFF TAC forks - once you realize you need to spend more time on the valving and oil heights rather than the air settings - the forks start to behave quite nicely and seeing how the bike is about 3 lbs lighter, and adding up what it takes to make that happen in other methods - I quite like them. No fork system is perfect - but pressure rise occurs on spring forks too.
  10. When all forks retiurn spring there will be air conversion kits someday.
  11. Generally they require richer across the board in settings. Seeing as the STIC also requires similar amounts of chsnge... 125 settings in the stic on a 250 are about right. that said there are a couple 125s i have tested on that will Nearly swap carbs between a 250.
  12. It always remains in the needle jet, if it comes out the needle won't go back in and hang the throttle. Since I file them... I had to locate where I needed to to be effective, and effective only at wot and 11/12 of wot. The mikuni needle is just about perfect in its location. The needle jet on stic has a small segment where it's necked to its outlet size. This is the location at wot the needle must be reduced... not above. You have an stic Halley?
  13. The step in the needle at the end ensures the needle is not a restricting element to fuel flow at WOT. ive found this to be problematic on some needles. You can richen main jet in large steps and see minor difference... until the needle is reduced at tip area. Mikuni, on the ball with this, produced some needles that have a tip step such that the main wot circuit is placed solely on the main jet and not some odd combo of main and needle combo. people will be surprised to hear that a properly jetted/needled bike will run perfectly up to 3/4 and often past that without a main jet at all. It's how I start jetting actually.. similarly to a "lectron" or single metering concept... if you spend enough time... you can make it run well without a main jet all the way to wot. However.. imho this is stupid... don't waste your time trying to do this. Jets and circuits exist for very good reasons... notably ease of tuning when you "know" what your doing. That part of the equation is of course much harder than anyone would like..
  14. I leans the very early portion of throttle opening to about 3/8 If this is a problem area for you it may be worth it - I suggest stepping into it like APBT did - half notch at first. If you spent large time on the straight diameter section of needle and all your settings - it's feasible it wont help much. I've found it to be very subjective to the user...which is true of all riding in general. Some love it, some cant' tell any difference, some may not "love it". But on the case reed hondas and ktm - especially in good working order with tightly sealed cases and good ring seal - where carb signal is good - Yes I like the notch.
  15. APBT, nice write up. It was incredibly observant of him on the powerjet bar location/angle. I have worked on quite a few of these, mostly yamaha and kx, but a few RM's, and never noticed the RM had the bar angled..... On our stage 2 carb mod, I'm removing the bar AND the air striker veins along with boring and tapers. Coupled with the STIC, this is great for power gains in WOT applications. But for 85 percent of the people out there - leaving the veins is a good thing - removing the PJ bar if not being used is also a good thing. The mikuni needle employs a stepped tip. I have been hand filing the keihin needle tips in our set ups to increase flow area at WOT. This has a few effects - and I suggest it for all users who are around 188 and up main size. From an all stock mikuni to the STIC - peak hp of around 10 percent is reasonable on the honda if you dont live in freezing temperatures. I can try to secure a newer style engine to test this on - but on the 02 and 03 models, we see about that result. Now - vs a very well jetted mikuni - no way. But the daily variance and head ache of getting the mikuni this good is a pain- as most people know the keihin is great as is - and the STIC is icing on that cake IMHO. The squish mod to a cr is good as all know - but not as much in peak HP as people think. On the 05-07 I suggest .045", and 50 ish percent band with +2 degree angle (about 10 deg cut) and small blending radius - and keeping compression in check around 13.2:1 uncorrected...which runs on pump usually. I've found that head mods require timing mods - for reasons not worth going to heavily into - but you may be surprised to need more advance on a tighter squish. Lastly - I've found the cr's and KTM's to run on pump gs with the STIC - so if you wish to wean down to less and less race fuel APBT - you can. This year continues to be swamped for me...finally seeing light at the end of the tunnel on getting some work out of the way...and with that will come more objective tests - with more data in various forms.