Ted, Although I don't have any experance with the 493, I do have experance with the Kawasaki and the 494. I have had simular experances.
First you don't say what kind of fuel pump you are using. Could make a difference. Have you checked to make sure that both carbs are opening evenly and are both getting wide open ? I suggest completly dissambling and cleaning both carbs and make note of what jets and needles are used. Make sure they are the same. I had a some dirt on top of one of the flot valves and almost drove me nuts trying to figure out why the carb would work for a while, the just shut down. The dirt would move in front of the valve opening and block the fuel then drift away and allow fuel in. Some engines just require different size jets in the carbs because of the desgin. The 494 does, maybe the 493 also. Make sure you have a good ground path between the coil ground and the engine. That spark current has to go some place. You should do a temp reading test on you EGT probes/display. Use a propane torch on the probes and a precise voltmeter to check the EGT output and the actual readings. Richard ----- Original Message ----- From: "Ted Rudolph" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Sunday, July 02, 2006 11:19 PM Subject: [F500] (no subject) > Anyone else having trouble tuning a 493? Can anyone give any insight into > properly tuning one? > > My engine (new from Tony Murphy in 2004) was running pretty well last summer, > although at the last race of the season (the Fun One at the Glen) the PTO > cylinder did not come up to temperature as quickly as the Magneto side. If we > let the engine run for a few minutes, did a lap around the paddock & then > changed the PTO spark plug the engine would run fine. Once we finished out > warm-up procedure it would run great - in fact, it was very fast all weekend. > > We didn't do anything over the winter except remove the balance tube and plug > the holes. This year at the Pocono Double the engine was a bear. Same > problems getting the PTO cylinder to come up to temperature, although changing > the plug after warming didn't help things. The PTO plug would be wet when it > came out, while the Mag plug was a nice milk-chocolate brown color. > > During the first on-track session, the Magneto Cylinder temp would spike high > (1500) at full throttle, while the PTO side would drop to nothing. If I > breathed the throttle a little, the cylinders would drop back to normal > (although the PTO was still low - 800-900 degrees vs. 1200 on the Mag side). > > Between sessions we went to richer jets - the only ones available were 340s > (thanks again to Steve Moore!) instead of the normal 290s. It ran 'better' in > the afternoon on the bigger jets, although a bit cool (EGT) and it certainly > lacked top-end power. > > Next morning we moved the needles (stock needles) to lean the engine back a > touch and it ran better at the start of the race, but after five laps behind > the pace car it was loaded up and took the last two green laps to clear out - > but boy did it feel fast on the cool-down lap. > > At Pocono we tried swapping the Carbs, the plug wires from the coil, swapping > the reed valves and swapping the rubber carb flanges/reed covers (all from the > PTO to the Mag side & vice versa). None of them fixed the cold PTO problem. > Likewise, we also did a compression test - both cylinders showed 120-125, so > they weren't totally out of whack. > > Anyone have any ideas? All that seems left is the actual cylinders or the oil > circuit (too much oil fouling the plug? Can it become unbalanced on one side? > > I've read the Mikuni manual and it hasn't helped any. Is there a better > 2-stroke tuning/performance book available? > > Thanks, > Ted > #98 Raptor, NE Div > _______________________________________________ F500 mailing list - [email protected] To unsubscribe or change options please visit: http://f500.org/mailman/listinfo/f500 *** Please, DO NOT send unsubscribe requests to the mailing list! ***
