Idle rises 500rpm when I lift my K75S tank????

[moto949]

Hi folks, I've been trying to track down a flat spot (2500-4500 rpm) for some time now. Today I noticed that with the bike warm and  idling, when I carefully lift the tank to try the lean drop method (with the air box allen screw), the idle jumps up. I've adjusted this allen before to minor yet worthwhile results (in quarter-turn increments), but always with the engine off.  This time, with the engine idling, I noticed the rpm increase a full 500 rpm. It drops back down when I place the tank down. I looked closely at why this happened but saw no pinched lines etc. It seems to happen when the tank loses metal contact with the bike, so I'm guessing a bad ground. Is this normal? If it doesn't affect the flat spot, I guess it's ok to ignore it, yes?

[The Mighty Gryphon]

Are you absolutely sure that you aren't disturbing the throttle cable where it runs under the tank???

[moto949]

Thanks for the quick reply.
     Found the problem! Not the throttle (it was unaffected by lifting the tank), but a good guess.
     Turns out the line adjacent to the main fuel line (to the fuel rail) was getting a bit folded in that very last quarter inch of lowering the tank back down. I guess I was riding around all this time with a pinched hose. I couldn't see it under there, and it sure looked like it had lotsa room under there, but when I bend it, it drops the idle 500 rpm. Unbending it (such as when lifting the tank...) the idle jumps up. Proof enough for me.
     Looks like I gotta free up some room under there somehow so this hose won't bend. And since it was affecting the idle, I have to reset the EFI again and hopefully find that flat spot gone for good!
     Thanks!
     

[Martin]

I had a very similar problem, it's due to fitting a non OEM return line. The OEM line has preformed curves, my non OEM would collapse where it goes back into the tank on 40C days. I cured it by fitting a Unicoil.
Regards Martin.

Unicoil 2.jpg (34.03 kB . 500x375 - viewed 408 times)

[moto949]

Great idea!
   I'll get that and some new hose about an inch longer than the one the last mechanic used, which probably caused the kink, too.
   I already trimmed the mechanics new 'S' hose before which, due to its 1/4 inch too long length, kinked as well! That made it run a bit better.
   May as well get new hoses for the other lines from the FPR.
   By the way, if anyone out there has air leaks at the thick rubber manifolds at the throttles (does your idle change when you spray starting fluid on them? *Keep a fire extinguisher handy for this test), you can try Permatex's leak spray. I did, since I didn't have time to swap out the rubber pieces. It worked so well that the next time I started the bike, it barely idled since it was tuned, unknowingly, to idle while compensating for the leaks! With less are creeping in, it wouldn't run at those old settings. I got out the Motion Pro Sync tool and reset the screws and all was better. *You may have to get a little creative to get some of that Permatex on the far side of the rubber manifolds - I used a rubber hose over the spray nozzle and bent it to reach back there.

[alexg]

The OEM fuel hose has a molded in elbow. It is worth buying that one from the stealer.

[johnny]

greetings...

im not smart... i only know what i learned from timtyler...

with that being said... i would use flexseal instead of leak spray... you wanna seal it up not make it leak...

also learned that snowflake with itchy butt has stinky finger...

j o

[moto949]

Thanks on the good advice on the oem hose, Alex - worth it, I suppose but I'd say the coil would fix the mild bending issue well enough. Besides, I just ebay'd the coils in a multi size kit....


And Johnny, you're right, and I sure hope the Permatex leak spray doesn't "cause" a leak any more than a fireman's "fire" hose causes fire... LOL.


Seriously, the Permatex Leak Repair worked well, plus it's clear... and doesn't have annoying commercials that I'd be paying for.