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pmdental(at)btinternet.co
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 Posted: Sun May 09, 2021 1:32 am Post subject: Idle adjustment |
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Hi Everyone,
Advice on how to adjust the idle speed on my 912ULS please.
The engine is 4yrs since installation with about 80 hours running time.
Runs good as gold but recently noticed idle speed is up to 1800/1900 rpm !
Do I adjust this by simply repositioning the throttle cable (quite possibly stretched now) or can it be adjusted by a screw on the carb ?
Thankyou Paul Munford G-OVPM
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JonathanMilbank
Joined: 14 Apr 2012
Posts: 390
Location: Aberdeen area
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| Posted: Sun May 09, 2021 7:11 am Post subject: Re: Idle adjustment |
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Hello Paul,
First I would suggest that you refer to Europa Mod.20 Throttle Closed Stop. If I recall correctly, this mod is intended to prevent strain on the 2 throttle cables by creating a physical barrier in the cockpit, on top of the tunnel and at the rearward limit of travel of the throttle lever.
I deliberately made my cockpit throttle stop adjustable and also screwed back the idle speed adjusters enough on the two carburettors so that they don't have any role in adjusting idle speed. My adjuster is simply a penny washer, edge filed with reducing radius ( a spiral, or cam ) to result in an eccentric around the washer hole, through which the rear screw supporting the throttle quadrant box is fastened.
To adjust idle speed, I slightly loosen the screw and rotate the penny washer as needed to alter the rearward throttle limit, before locking the screw again. The eccentric penny washer and screw head are covered by the fabric covering the tunnel, which can easily be pulled a little aside for adjustments.
But you should check the balance of your two carburettors with some good device like a CarbMate. Usually it can be seen that the two carburettors aren't idling exactly the same, so if you want a slower idle then use the cable adjusters where the cable outer sheaths meet the carburettors and take whichever carburettor is "higher" down slightly. Or vice versa if you want a higher idle speed.
It can be a bit fiddly, with cable adjustments being made maybe one flat at a time ( 1/6 turn ) using the adjusters, before relocking with the little nut after every little adjustment and then restarting the engine. The end result should be that your carburettors are synchronised and the desired idle speed is achieved when the throttle lever in the cockpit is fully back against the stop. Thus also no strain on the cables.
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Griffo
Joined: 18 Mar 2021
Posts: 70
Location: The Oaks, NSW, Australia
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| Posted: Mon May 10, 2021 4:04 am Post subject: Re: Idle adjustment |
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Hi JonathanM;
I like the sound of your idle low speed stop - any chance of a photo or two.
On the carburettor balance - here is absolutely no need to go to the expense of a "Carb Mate" any half decent motorcycle shop (or on line) will sell you a pair of cheap vacuum gauges and the bits to adjust down the inlet pulses. Then all you will need are two suitable lengths of tubing, so that you can monitor the vacuum in each carbi, in the cockpit. Don't forget to disconnect the balance tube befor making your readings Oh and do your static/manual adjustment befor doing your pneumatic fine tuning. Simple as!!.
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JonathanMilbank
Joined: 14 Apr 2012
Posts: 390
Location: Aberdeen area
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| Posted: Mon May 10, 2021 4:27 am Post subject: Re: Idle adjustment |
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Sorry that the aircraft's away for a while, being used by a friend elsewhere. A photo wouldn't be much use, because it's up to each person to make a penny washer into a gentle spiral / cam by filing the edge progressively nearer to the washer hole, about halfway around the circumference.
It's trial and error, to suit the distance between the back of the throttle lever and the aft bolt holding the throttle quadrant box in place. Another way to do it might be to follow the instructions in Mod.20, making a plate as shown but slotting the bolt hole to allow fore and aft movement of the plate.
My method with the penny washer is similar but on a smaller scale to the rotating parking brake methods I've seen on a couple of Europa monos.
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budyerly@msn.com
Joined: 05 Oct 2019
Posts: 288
Location: Florida USA
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| Posted: Mon May 10, 2021 5:55 pm Post subject: Re: Idle adjustment |
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There are photos of my throttle stops for both the 914 and it also works for the 912 series Europa Throttle box on the Europa Club website Builders section Bud Yerly notes Throttle friction is the title.
Over the years I have done this mod and it is simple and it works.
Normally I set my idle to about 1600 hot on a warm day at the carb stop. Then bump the throttle stop up to 1800 for winter and about 1700 ish for summer.
Warning, you may need to crack the throttle on the 912S a bit to get up quickly to 2000 RPM otherwise it will shake like the dickens when on a cold start.
Best Regards,
Bud Yerly
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