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Author Topic: Idle not reving down  (Read 629 times)

fermin

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Idle not reving down
« on: April 24, 2010, 08:48:03 PM »
Back to the forum after being away for 2 weeks in S America.  Opened my box of parts and replaced the lower accelerator cables.  Problem is I cannot get the rpms to return to idle after reving the motor up.  The springs return to the 'down' position but the rpms stay high and then come down 5 seconds or so after the throttle is closed.

The bike had the same problem before the cables were replaced but for another reason, one of the cables was bad and did not allow the tension spring to return.

Carbs have been rebuilt (except for the choke).

Also, theres about a 1/2 in of play in the throtle before it engages.  Can this be reduced?.  

On a side note, after removing both grips, two small aluminum wedges approximately 1 cm long fell.  They appear in the parts diagrams but no idea where they go or their purpose.

As always the help is greatly appreaciated.

Offline nhmaf

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Re: Idle not reving down
« Reply #1 on: April 24, 2010, 09:47:39 PM »
There are wedges to help keep the control perches in place without overly tightening the screws, and possibly cracking the body of the perch.

Does your throttle grip somewhat "snap" back to position if you open it and just let go, or does it slowly "creep" back of its own?    If the cables aren't binding/snagging you may have a dry/dirty throttle tube/chain or the teeth in the internal sprocket may be worn out and binding.   This requires carefully taking the throttle controls carefully apart, cleaning, inspecting, and lightly greasing/replacing parts as needed.  The sprocket must be put back in a specified position to work properly.

There is a procedure for synching the carb cables that you need to do after replacing the cables - have you done this?
Airhead #12178 ? BMWMOA #123173 ?BMWRA #33525 ?GSBMWR #563 ?1982 BMW R65LS ?1978 BMW R100/7 1998 Kawasaki Concours

Offline montmil

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Re: Idle not reving down
« Reply #2 on: April 25, 2010, 08:25:11 AM »
Quote
...Also, theres about a 1/2 in of play in the throtle before it engages...

The cable adjusters on the carb tops are for adjusting out slack and the required synchronizing of the carbs at idle and running rpms. If you have the single throttle cable at the twist grip, there's also an adjustment feature on the end of the cable splitter under the fuel tank.

If you have opened the twist grip "gearbox", the gears must mate in a specific position. Look for the tiny line-up marks hidden under the grease. Check your manual.

Please include your bike's vintage with your questions. Perhaps post the info on the signature line of the avatar.

Monte
Monte Miller
Denton, TEXAS
1978 BMW R100S
1981 BMW R65
1983 BMW R65
1995 Triumph Trophy
1986 VW Cabriolet

drewboid

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Re: Idle not reving down
« Reply #3 on: April 26, 2010, 11:22:26 AM »
Often the trouble is sticky weights in the ignition advance unit (bean can). much discussed on this forum - do a search.

fermin

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Re: Idle not reving down
« Reply #4 on: April 26, 2010, 09:58:51 PM »
Readjusted the cables and got it to idle down OK.  Was finally able to run it around the block for the first time since I bought it nearly 2 months ago.  Theres a light at the end of the tunnel.

Thanks for the help