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Author: Subject: Westfield Megabusa Throttle Body Synchronisation

posted on 30/3/18 at 11:17 PM Reply With Quote
Westfield Megabusa Throttle Body Synchronisation

I followed the Haynes manual for the Hayabusa engine on a bike so a quite a few steps were not required and they seemed to over complicate the procedure. Couldn’t find a how to on the forum so thought I’d knock this up.
I’ll try and shorten it and make it a ‘dummies guide’.

Firstly check your idle speed is correct.
Let the engine warm up to a normal operating temperature.
Turn off the engine.
Remove your air filter / box and use some old tights and elastic band to secure around the top of the trumpet to act as a temporary filter.
Disconnect the vacuum hoses from the throttle bodies, they might be unwilling to come off due to the heat. (See pic)
Fit the vacuum hoses. (See pic)
Fit blanks as per pic.

This where I struggled as when I was trying to start the car, the engine just wouldn’t fire up and run.
You have to disconnect the vacuum plug from the sensor, think officially it is called IAP sensor.

Once this is disconnected the engine should start.
Check on your gauge to see how balanced they are with each other. The actual reading doesn’t matter as long as all balanced.
There are 3 little screws, 1 between 1+2, 1 between 2+3 and 1 between 3+4. See Pic.
You balance butterfly valves 1+2 with each other by turning the screw between 1+2 valves.
Then balance butterfly valves 3+4 with each other by turning the screw between 3+4 valves.
Then you turn the screw between 2+3 to balance valves 1+2 with 2+3.
I adjusted my idle speed after balancing up as idle speed had lowered off.
Once happy, put at all back as was before you started.

I am very annoyed as took a picture of my vacuum gauge before I set mine up and they were way out as expected as my engine sounded a bit lumpy on tick over / idle, revs hunting a little.
I deleted it by accident when I was deleting some of the blurry photos I took of the vacuum gauges after I had set them up! So done a little Microsoft Paint job to show approximately where they were before adjustment.
My throttle bodies are now within 0.5cmHg of each other. Engine sounds sweet as a nut now. Can’t believe what a difference that 30mins of relatively easy tinkering has made…
Hope this helps somebody out.






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posted on 31/3/18 at 09:23 AM Reply With Quote
Nice write up,easy to read and understand
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