80GS overrunning

[graffiti]

Hi all,

My 1987 R80GS continues to intermittently overrun despite all attempts to cure it.

It does do it mostly during a longish run.

I've adjusted both throttle cables which seemed to sort it for a while..it's not the carbs either as I've stripped them down and all ok!

Anyone experienced this problem and any advice??

 

[DrFarkoff]

What do you mean by over run??

rev faster than it should at tickover??

If that's it?? Then did you originally set the carbs up when the engine was at working temp (15 - 20 minutes riding time NOT idling in the garage time)

When was the last time you adjusted valve clearances??

 

[graffiti]

Hi,

Thanks for the note,

Yes revving faster than idle speed..

Carbs balanced at engine temp, ridden for half hour and then rechecked.

Valve clearance done less than 2000mls ago..

 

[Kenny]

If you've checked those then probably the throttle cables ( ensure both throttle and choke return fully with about 2mm free play in all the cables ). Does the 'excess' throttle return if you turn the throttle fully off ( turn it doen't just let it return by itself ).

 

[Wrigsby1]

Rob Farmer et al advice of getting the bike up to temp and then adjusting the air bleed screws for highest tickover on each carb and then adjusting the tickover down via the butterfly adjusters worked for me...

 

[graffiti]

HI,
Thanks for that, I found the following on a US site:

"High idling rpm, perhaps it came on slowly worsening, is often the cause of one of two problems. Occasionally from both. One of these problems is a sticky automatic timing unit in the ignition canister at the front of the engine. The other problem is leaking intake manifolds or mis-adjusted carburetors (usually the idle mixture screw) or, no slack in one or both throttle cables."

I think it may be a sticky timing unit as I have replaced and double checked the cables and a previously mentioned I have rebuild the carbs and set up all the balance.
I seem to remember a member had a similar problem with a sticky timing unit...any advice on how to replace the grease would be appreciated.

 

[Wrigsby1]

HI,
Thanks for that, I found the following on a US site:

"High idling rpm, perhaps it came on slowly worsening, is often the cause of one of two problems. Occasionally from both. One of these problems is a sticky automatic timing unit in the ignition canister at the front of the engine. The other problem is leaking intake manifolds or mis-adjusted carburetors (usually the idle mixture screw) or, no slack in one or both throttle cables."

I think it may be a sticky timing unit as I have replaced and double checked the cables and a previously mentioned I have rebuild the carbs and set up all the balance.
I seem to remember a member had a similar problem with a sticky timing unit...any advice on how to replace the grease would be appreciated.

According to one of the US internet "experts" on Airheads the sticky timing unit is over-diagnosed and as Rob Farmer said the air bleed/idle mixture screws will wear/muck up with age and will not be set as standard... As the latter takes a few minutes ot try then have a go at that 1st... I will look back for the thread...

Kerrrching...

http://ukgser.com/forums/showthread.php?t=339009

 

[Steptoe]

According to one of the US internet "experts" on Airheads the sticky timing unit is over-diagnosed

Another favourite diagnosis of the internet "experts" is a "stuck or sticking valve".

FFS, put the books down and get some "hands on" knowledge.

 

[Devon]

My idling problems turned out to be badly routed cables after restoration. If I bounced the front of the bike hard on the front brake, the idling settled down as the cables went back to where they should be. I understand the bean can is timing not idling.

 

[Canuck]

My idling problems turned out to be badly routed cables after restoration. If I bounced the front of the bike hard on the front brake, the idling settled down as the cables went back to where they should be. I understand the bean can is timing not idling.

Maybe thats why mine is doing the same Which cable did you end up moving?

 

[Wrigsby1]

Another favourite diagnosis of the internet "experts" is a "stuck or sticking valve".

FFS, put the books down and get some "hands on" knowledge.

Working on it... and my BMW self branding technique when fixing the running of a Boxer...

If we believed the US jockeys we would be stripping the bike annually and using Optimol as piles cram as it seems to do every feckin' thing else...

 

[Rob Farmer]

If we believed the US jockeys we would be stripping the bike annually and using Optimol as piles cram as it seems to do every feckin' thing else...

It does its brilliant stuff

If I'm being really anal, especially with 40mm carbs, I balance the carbs using the tickover screws to give a high tickover of around 1200-1500 rpm then turn the mixture screws on each carb to give the cleanest running and then reset the tickover to around 900rpm. Always works a treat and does away with any stumbles just as you open the throttle.

 

[Rob Farmer]

Graffiti,

Strip the carbs and give them a good clean, especially the left hand carb, the breathers drip goo into the inlet tract, it gets into the pilot air passage causing all sorts of strange running issues. Set the float height while your in there and fit a new float bowl gasket.

Make sure the o rings on the pilot adjustment screw, pilot jet and main jet holder are in good condition.

I'm doing mine at the minute so if your not sure ill take a few snaps as I go along.

 

[Roger Chatterton]

Rob helped sort out my fast tick-over problems a treat - was a combination of dirty carb jets, and also the beancan weights were not returning fully, which caused tick over to rise up to about 2500 -3000rpm. When I switched off the engine at traffic lights early in morning in Melton Mowbray, and then re-started to move off on green, made a backfire like a gun had gone off. Brilliant. All fixed now though !
Not a big job at all to check the bob-weights, and apply a bit of grease round the pivot points. Do NOT spray WD40 in there though.

 

[graffiti]

Thanks for the advice guys, I'm happy with the carbs, completely stripped them down and cleaned/renewed jets and balanced etc...and the throttle cables cables..

Roger, thanks for the advice on the beancan weights, especially NO WD40 just grease! Will probably check this out next..

Cheers

 

[bernardofeio]

hello

I had a similar problem with my R100GS. After getting hot the bike was revving faster than idle speed. I tried to fix it by cleaning and adjusting the carbs but it was never 100% fixed.


After one trip to Marrocos were the bike was reaching very high temperatures even at high RPM I was getting revving problems leading to huge flames in the exhaust and scaring all camels around! )

back home I've changed the bean can and never had that problem again...