I posted this over on All Things Moto, but I wanted to post this on Thumper Talk as well just to see if there were any other ideas. The ideas that were offered over there, I will have an opportunity to look at this week and hopefully put them to bed. Those were: possible damage to the insulating boot around the plug (which may also be fluid/oil build up in the plug valley - although my weep hole is clear to drain), possible pinching of the vent lines from the carb when the swing arm droops and verify if the baffle around the jets is in place (which I believe it is but will verify). Outside of these good ideas, I wonder if anyone else has had direct experience with a problem like this and could shed any additional light. At the very least, if the problem is a product of one of the ideas mentioned, then this thread will simply become a good problem/solution thread to archive on the forum. Thanks for any incite or helpful advice.
A simple description is that once this bike leaves the ground, it practically shuts off, lands and then stumbles back to life. The symptom is very repeatable and renders the bike almost useless as its just a matter of time before it pitches me over the bars. What I can say, is that the bike runs quite well when on one or two wheels and will do this problem only when completely airborne.
What I've addressed for this issue specifically:
- The rear wheel spins freely - brake and bearings are not dragging
- I'm not unknowingly standing on the rear brake - I've adjusted clear out of reach just to prove this to myself.
- Numerous carburetor adjustments including JD Jetting kit (170 main and 45 pilot - I live at ~1000ft elevation with 95*F average summer weather), JD Jetting Red hot weather needle, JD Jetting brass air/mixture screw with new o-ring (2-ish turns out), o-ring mod to AP, QS3 tunable leakjet on AP (3 turns out), carb cleaner stall test on intake and manifold boots (no leaks), full rebuild clean/clearing of all jets and ports.
- new OE exhaust gasket
- running with and without TPS plugged in - runs better with and has no affect on issue
- confirmed/measured accurate float height
- petcock fuel delivery has good flow and float valve works fine.
All of these adjustments have made vast improvements on the general performance of the bike. It always starts up and runs like a banshee without breaking up. The sudden power loss on take-off leads me to believe the issue is electrical, but the bike never ran so great when I first got it, so the aforementioned carburetor changes helped there. All that is left is this one stupid symptom otherwise the bike runs brilliant.
Please help me figure this out. I am forced to trail ride the bike only in the mean time and anyone with a 450 knows, they need open space. I don't want to sell it and pass the problem off b/c that is not right and I will not be foiled by something I just didn't consider.