SuzukiHayabusa.org
TECHNICAL => ALL MOTOR TALK => Topic started by: LVBUSA on October 19, 2015, 09:42:43 AM
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Had a friend that had gummed up throttles from starting every so often. Injectors got to leaking, and fuel went South. Sent injectors to RC, cleaned intakes, cleaned out tank and pump, validated fuel pressure, and disassembled throttle bodies. This is the motor that has the filter assembly we spoke earlier of, with validated pressure.
Pulled all linkage arms off, soaked and cleaned each throttle body individually. #1 and #2 were badly gummed up, wouldn't close on their own. Pulled TPS on #1 and reinstalled on clean, free pivoting throttle. All four were nice and clean when I reassembled throttle bodies in exact order. Reinstalled all springs, and reinstalled group. Set TPS via dash/dealer mode.
Fired motor and it seems like throttles are not returning to full closed. Idle is at 1500 with screw completely backed out, can roll grip forward and lower idle to some extent. Let off grip pressure, and idle wanders back to 1500.
Just wondering if maybe I over-tightened throttle shaft nuts, or maybe the number 1/2 throttles are out of synch with 3/4 due to disassembly. Anything basic that I am missing here ?.
Have not installed Mercury stix to tune throttles. Motor has not been up to full temp yet.
Will run motor up to temp tonight and see what vacuums are doing.
Thanks for the read, A.
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Problem solved, interesting things discovered for anyone disassembling their throttle bodies and trying to do static prestart settings.
In the process of the reassembly, bear in mind that although you have not touched the linkage adjustment screws the adjustment has changed. Even if you feel you have been meticulous at the disassemble/reassemble, there are unnoticed factors at work. How the linkage brackets are torqued, and just removing them in the cleaning process you have changed their original orientations. Reassembling the bodies at their through-bolt mounting points (the three long bolts and their nuts and washers) there are also changes in linkage orientation to a certain degree.
Once reassembled and installed, you now have a slightly changed configuration. Starting the engine may bring an uneven, or even rough idle characteristic.
Once I hooked up my Motion Pro Mercury tuner, I discovered first that #'s 1 and 2 were running extremely high. Secondly I found that #'s 3 and 4 were almost closed. So my jumbled idle was mostly due to two cylinders doing all the work. Once I cranked the main idle screw open a few turns, and cranked 3 and 4 down to match, the idle magically got smoother and more cooperative. The rest is light screw adjustments to the new linkage arrangements and this Busa is in the game.
Moral of the story, don't trust any ideas that if you reassemble the throttle bodies perfectly that you haven't changed something. Second moral, don't try and go by feel, get a throttle tuner set so you can see what is really going on from the first hit of the starter. :thumb:
A.
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Great post, thank you.
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Great post, thank you.
What he said :thumb:
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I used to use a set of Mercury Tuner Sticks on my old 98 ZX9R and could adjust all four cylinders within a pound or two. And they worked fine..........that was with carbs.
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What's a carb?
:hys: