Tuesday, January 18, 2011

Introduction To Motorcycle Maintenance - Low Idling

The following is an excerpt of a diagnostic troubleshooting for a modern sportsbike with low idling/stalling. I happened to encounter this with my 2007 Suzuki GSXR 600 recently and thought I'd share how I went about solving the problem:


   
My mechanic and I figured out after much trial and error, that I needed to get my valves adjusted (this job was extremely over my head). He ended up replacing 10 of the 16 shims and adjusting the other 6 to specification. My bike has 8 intake and 8 exhaust valves, so 2 intake and all 8 exhaust were bad. My bike has ~27,000 miles on it and has NEVER had the valves even checked.
For the novice, please let me explain. These high performance engines require lots of maintenance. And not in neglect, but in ignorance did I miss checking the specifications of my valves. I just never heard about this type of maintenance and simply kept riding.


Below is a picture of the rpm meter:


At high rpm's (much higher than your average car) the engine wears out much faster, and when the valves become out of adjustment you can lose your engine in ~30,000 miles.
Mechanically I'm pretty competent - I DIY (Do It Yourself) all of the following on my gsxr: oil & filter change, air filter change, spark plug replacement, coolant drain, flush, and replacement.

A high performance engine will certainly impact the shims of the valves as they loose millimeters affecting power output greatly. 

Typical Valve Adjustment Values (quoted from my mechanic):
Ducati = Every 6k
Suzuki = Every 15k
Yamaha = Every 26k


If the motorcycle is struggling to stay idling, one of many things could be wrong:

1. Turning the idle a quarter turn clockwise to raise the idle and see if it solves the problem.
2. Air filter & spark plug replacement. If the engine can't breathe, then it will stall also along with gas mileage being affected as well. This is usually a good indication of a bad air filter and/or spark plugs. 
3. Secondary butterfly valves by the throttle body could be stuck closed. They should open wide when the motor is cold. 
4. If the secondary throttle bodies move then reference your motorcycle make's forums on how to check to see if your TPS (Throttle Positioning Sensor) is working correctly. You might also try the bike's dealer mode (look this up on forums, usually a paperclip connection under the seat) to see if it throws a code letting you know your TPS is bad.
6. If all this fails I'd then start thinking about your valves and getting them adjusted with some shims replaced.



For Suzuki the idle rpm should be about 1200-1600. For Yamaha, this R6-forum explains how to adjust the idle:

"The idle adjustment screw is on the right hand side of the bike right under the fairing. Basically if you are sitting on the bike, (riding position) it would be right under your knee. Turn it to the right to turn up the idle. Have it idle at about 1,000 RPM. Or maybe try a little lower, and work it up little by little until it can hold steady."



Great starter forum sites depending on your Make:
Suzuki: http://www.gixxer.com/
Yamaha: http://www.r6-forum.com/
Honda: http://www.600rr.net/
Kawasaki: http://www.zxforums.com/

Welcome to the world of DIY! Be prepared to save lots of money and still make this hobby affordable!

-RazorMD

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