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Originally Posted by STB
If I get my gaskets in this week, I will put the stock TB on and tune it this weekend, gods willing, and sooner or later report on stability and TPS/IAC adjustability. If it is unstable with the stock TB, I guess the SERT is on the horizon since at least a few local mechanics have immense experience with the SERT. I just hope the stock TB can handle a little bit of the engine demand since my cams don't turn on till 2700 rpms just when the stock TB might run out of air on a 4.25" bore. I ought to be able to make 110 hp with the stock TB, if so, it should work through midrange rpms. We shall see.
STB
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I finally got the gaskets in and completed the project. The stock TB is back on the bike. I took off the Kuryakyn 57mm TB.
Verdict: Darned good.
I kept the map developed with the 57mm Kuryakyn TB and put the parameters on open loop. I put the TPS at nominal. I fired it up and it started on the first try. I looked at the IAC and it started at 70 with ambient temp at 88 deg F.. It only moved, every so slowly to about 60 at 110 C ET. The Kury never acted so slowly and smoothly. I turned the throttle stop about 1.5 revolutions to open the butterfly. I reset the TPS to just below midrange of nominal but within specs. The IAC hit 30 at 115 C ET and was steady as a rock and stayed there till I shut it down at 120 C ET. I restarted the bike several times and everything was stable with no variation except the IAC maybe went to 32 at 118 C ET. Very stable. All this was done in the garage and nothing done on the street yet. That's the next step. I am off for a ride!
BTW, I put the parameters back to closed look and reduced the horsepower estimate 6 hp or so. I left the injector parameter at 6.1 gps since I am using the 6.1 injectors on the stock TB. (These injectors were flowed by Marren Injector Service at 6.1 gps at 58 psi which is HD fuel pressure. Someone told me they should have been flowed over 58 psi to arrive at the standard flow rate. I don't know about that, yet). Idle could be reduced to 930 rpms and it was as smooth as butter. The rpms are at about 1100 which is Ok for a 4.25 inch bore engine.
The only slight concern is that the stock manifold does not have as much play/neck length at the gasket/flange area; the Kuryakyn has more length. Therefore, the flanges on the manifold do not butt up against the stop on the manifold since, apparently, there is a bit more spread on my cylinders than stock. (Probably, the cases are bored at the spigot a bit wider than stock which spread out the cylinders an extra 1/4 inch or less between both front and back cylinder intake mating surface on the heads 'cause we measured it....... ).
My impressions: this is the way it should work. It was tuneable as it should have been all along in that the sweet spot on the IAC was easily found and never varied inexplicably. I will see what day two and day three bring and report back.
Am I down on the Kuryakyn. No since after 12 months of troubleshooting the Kury, I finally got it working even though it would inexplicably vary (but less than before) and finding the IAC sweetspot was purely magic which I could find after lighting incense and muttering a mantra. The 57 mm Kuryakyn is in its third stage of product revision. Stage one had screws that were too large for the throttle body shaft and the shaft would crack, if your engine backfired, at the screws holes in the shaft. Stage two used smaller screws for the butterfly mount to the shaft to prevent shaft breakage on backfiring. Stage three, supposedly, will have different material for the butterfly shaft. Kuryakyn has treated me well in that they want my TB back to look at it. They are sending a new stage three 57mm TB even though I am 3 months out of warranty. No complaints about that.
STB
