1983 R80G/S hot idling problem.

[Devon]

My R80G/S starts fine and runs smoothly ticking over at 1k rpm for the first couple of miles when it is cool but as soon as I have done 5 or 6 miles and got everything hot the tickover sticks at 2.5/3k rpm, before dropping very slowly back to about 2k rpm.
I have checked the rubber inlet pipes either side of the carbs and they seem a snug fit and shouldn't be letting any air in and I have checked the carb diaphams this morning and they appear in good order.

The bike can be put in gear and the engine stalled down to about 1200rpm where it sits OK until I blip the throttle and then the tickover remains high again. Plugs are a good colour so mixture isn't far out.

Can anyone give any pointers what the problem might be? I am not good with carbs

 

[Canuck]

Hey Devon... I'm having the same issue although it only occurs after longish runs (30 minutes). I'm not thinking of a carb issue as they were rebuilt just before I got my grubby mitts on the bike. I was hoping to get some help sorting it at the airhead weekend coming up.

 

[Kenny]

Need a tad more play in the ( hopefully lubed ACF50 ) throttle cables

 

[Rob Farmer]

Make sure you have free play in the throttle cables and then balance the carbs. Take it for a good run to get it to the normal running temperature, pull over and tweak the pilot mixture until the revs peak, one carb at a time. Once you have the optimum setting use vacuum gauges to set the tickover at the right speed. Go for another run and do it again. Hopefully you should be sorted by then.

Don't worry about the mixture screw position they seldom work properly if you set them as the manual recommends. Wear, different filters, non standard exhausts etc all mean the standard settings little more than a starting point.

 

[John Roberts]

Have you tried pressing the lever on the throttle butterfly valve to which the throttle cable is connected to see if they are actually closing fully when the throttle is closed?

 

[DrFarkoff]

If you don;t have them up to operating temperature when you set them up they will rev their nuts off when hot

AS for stalling when cold

They all do that Sir!

When hot tickover 900 to 1100 whatever it's comfortable with


If you haven;t done a service recently also check the clearances I have come across a few that "leak" air in somewhere because they were set too tight and once it warms there's no clearance

 

[Devon]

Thank's for the all the advice. I was hoping to get along to the Airhead weekend and have a go at sorting the carbs but I don't think I will be able to make it this year.
I will have a go at setting them later this week

 

[Canuck]

Devon... I have two spare sets of carbs if you fancy having a go at them ir you could borrow a pair while you rebuild yours. . Or pop around sometime and we can set yours up though a rebuild in a few hours may be out of the question.

 

[Devon]

Devon... I have two spare sets of carbs if you fancy having a go at them ir you could borrow a pair while you rebuild yours. . Or pop around sometime and we can set yours up though a rebuild in a few hours may be out of the question.

Cheers Canuck but I don't think there is a lot wrong with the carbs a bit of adjustment won't sort out. I will let you know how I get on.

 

[BillN]

Exactly what Rob Farmer said, but don't let the engine idle too long and overheat when you are adjusting the carbs ......... (or use a fan)

 

[ken brooks]

Andy, i note that you say that you can 'stall' the engine down to a tickover and then the revs hold steady? I had a similar problem and it turned out to be a sticky 'bean can'

 

[Canuck]

Andy, i note that you say that you can 'stall' the engine down to a tickover and then the revs hold steady? I had a similar problem and it turned out to be a sticky 'bean can'

And what was the solution?

 

[DrFarkoff]

And what was the solution?

Lubricate bob weights in Bean can thru the little alloy "window"

 

[Canuck]

Lubricate bob weights in Bean can thru the little alloy "window"

 

[Devon]

Well after all that, I have delivered the G/S down to Ocean BMW to display in their showroom and promote the Classic weekend 28/29th June as well as a talking point to advertise the new GSes in the showroom.
I will check the throttle cable slack, the bean can and set the carbs properly when I get the bike back in 4 weeks. Thank's for all the advice everyone

 

[BillN]

Lubricate bob weights in Bean can thru the little alloy "window"

If it is connected with the Bean Can swop it over to see if it is really the problem

 

[BillN]

Remembering back - there are various tests to test the timing unit - Snowbum, (Robert Fleischer) always explains it well

 

[crampie]

And very nice it is too!

Well after all that, I have delivered the G/S down to Ocean BMW to display in their showroom and promote the Classic weekend 28/29th June as well as a talking point to advertise the new GSes in the showroom.
QUOTE]


Thanks Andy - we've loved having it (and could have sold it a few times over!).

 

[The Other PaulG]

I've also been wrestling with this same problem (R100GS P-D).

One thing I noticed with mine was that whilst the throttle cables had enough play, because they're routed in a bit of a haphazard way, they sometimes shift and this restricts the free movement of the inner cable which then becomes slow to return to its slack position.

Just to be clear, there's nothing really holding the throttle cable in place between the headstock and the top of the carb (there probably should be!), so it sometimes shifts forward and you lose the ideal alignment between the cable and its direction of pull.

Sorting this out definitely reduced the issue on my bike.

However, the issue is still there a bit and just in case anyone has any smart ideas:
valves correctly set
no air leaks
no bean can
jets and air passages all blown through and proved clear
** bike starts easily in cold weather with no choke **
spark plug colours do not suggest rich running