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About APBT

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  1. Just curious- what did you use to clean your cases with?
  2. H4L has a valid point about Pro Circuit's work on the case reed engine CR250's. For around $300, the return on your investment is very good, especially if you opt for the C12 race fuel head with their porting. We sent a 2005 cylinder and head to PC and it was night and day better than stock. We sent a YZ250 cylinder and head to Eric a few years ago for 265 conversion. If memory sevrves, I think we paid around $500 for his kit that included: (1) boring the cylinder to 265cc, (2) nikasil replating (3) porting (4) head mod and (5) new piston and gasket set included. The price was very reasonable for the amount of work involved. The results were OK- some power was added in all rpm zones without appreciably changing the way it ran from the stock YZ250. However, guys should be aware that going to 265cc is going to require additional time to test and re-jet on every circuit from pilot to main jet from your original 250cc setup. The required jetting changes were surprising considering only 15cc of additional displacement was added. We have read many mixed reviews regarding Eric, but our experience was good.
  3. Harrperf, All valid points. Thanks for the input.
  4. We have had the chance to do a little more testing with the STIC. Background info on jetting, setup, etc can be viewed on this Honda 2 stroke link:https://www.thumpertalk.com/forums/topic/1234222-stic-block-review-2006-cr250/ We have seen very good results in the mid range, top end and over-rev rpm zones. Throttle response is clean and crisp with an enhanced ability to build rpm's more quickly and extend the over-rev zone. Good work here. Previously, we were slightly dissatisfied with the throttle response in the off idle to mid range transition zone. Derek Harris at HP Race Development suggested a simple cutout mod to the STIC hood which effectively emulated the stock Keihin cutout. We were able to accomplish this small mod in a few minutes with a Dremel tool. The results are excellent- improved off idle to mid range throttle response and crispness. Recent reports indicate that STIC has incorporated this mod into it's new units, so kudos to STIC for their effort. For individuals who own older STIC units, we suggest you perform the mod. If you are not comfortable doing the mod on your own- then HP Race Development, or maybe STIC should be able to help you. Being picky, we have also identified a very slight rpm instability in the idle to mid rpm zone. This instability is not noticed on an aggressive sand track, or high speed hard packed track where speed and rpm are kept up. However, in a scenario where the rider is attempting to navigate a slippery off camber turn on a wet clay track where precise throttle control is imperative, we have noted a very very slight rpm wandering effect. Not enough to be disconcerting, but slightly noticeable. We are sure that with additional testing, this issue will also be successfully resolved. In all, we are very pleased with the overall performance of the STIC.
  5. The vapor blasting process produces some very nice results on engine cases. https://www.restocycle.com/ http://noreasterblastworx.com/
  6. https://www.thumpertalk.com/forums/topic/1234222-stic-block-review-2006-cr250/ Good info in this Honda thread which might be of interest to KTM guys who are using the STIC.
  7. Mikuni tip detail. 9.1mm at this caliper opening Diameter 1.2mm in this section
  8. 48.1mm at clip 3
  9. Hallsy, it stays in just like Derek describes RM250 reference carb with Mikuni needle WOT
  10. Derek is right about this. Our testing showed the Mikuni needle to be better at WOT and over rev than the N3EJ. To compensate, went richer on the main jet which helped, but the Mikuni still seems like a better option for road racing, flat track, or an extreme wide open outdoor mx track. The STIC system seems to require a lot of fuel on the high speed circuits, at least in our experience. Another consideration besides the needle final diameter is the effect the angle cut on the pointed tip has on the spray pattern. Derek previously mentioned that he hand files the Keihin needles to compensate for their large final diameter. We'll probably send him one for this mod. If the Keihin needles can be made to match the performance of the Mikuni's at large throttle openings, it would be a home run.
  11. The 6BFY43-74 fully seated in a sample Kawasaki PWK slide. There is enough clearance on the clip outside diameter and needle groove OD to fit into the PWK slide even though the Mikuni setup is a few thousandths larger. If you're not comfortable with the amount of clearance at the clip grooves, you could always enlarge the hole diameter by a thousandth or two. The clip has plenty of space Note that Kawasaki machines in an idle bleed air notch in front of the needle at the slide base which allows for idle with less slide opening. RB will machine your slide to this spec for only a few dollars. I'm sure Derek can also do the same.
  12. Here's the Keihin N3EJ outside diameter at the grooves.
  13. Here's the Keihin N3EJ, Yamaha part no 4SR-14916-EJ-00 with Keihin clip attached, Yamaha part 4MX-14919-00-00
  14. Here's the Mikuni needle outside diameter at the clip grooves.
  15. Hallsy, Here's the Mikuni 6BFY43-74, Yamaha part no 284-14116-J4-00 with Mikuni clip attached, Yamaha part no 3MA-14159-00-00 Note the final diameter profile of this needle at WOT