Okay Where to next?? R80G/S carburation

[DrFarkoff]

A mish mash Hodge Podge of a Lovely wee scruffy Loveable Pile of Pooh! But it's a cracker

So the story so far delivered and abandoned I Did a once over inc comp check and pronounced it do~able

So fixed all the ancilliaries overhauled the alternator and starter and fitted new leads

Stripped carbs, blew out and cleaned all crud out of fuelways and fitted new diapraghms and floats (and set them), also did needles and pilot screw o rings and fitted a feck off big fuel filter to stop crud from tank.

Jets didn't look too worn when I tried the needles in them but something isn't right

She starts and Idles fine but when you rev up and release the cables are returning okay and the slides seem to be dropping okay

SO why won't she go back to tickover??? it remains at a very fast idle for a minute before it drops back

Intake tubes are fine and sealed and I can't detect an air leak and as I've said the compression check was good and fairly balanced but it's running like a bag of pooh again?

Timing is spot on and the valve clearances done too, although someone has done the zero clearance on one side to stop the rocker arms rattling off the posts

So before I launch into another whole strip and dismantle fest

Has anyone any useful and sensible suggestions which would be relevent to this wee motorcycle and it's present predicament?

 

[Noddy]

Bit of a long shot here, but had similar. Have you replaced the throttle cables ?

As I recall the single cable from the throttle runs into a splitter to feed both carbs. Have you cleaned it out ? I had one that was so full of gunge that it would only close very slowly. Everything look correct but they were hanging and very slowly returning as the slider pushed the gunge back up the cables.

Have you tried to manually close the cams/cable connections at the carb end after giving it a few revs ?

Sorry, a few questions but I'm only trying to help.

 

[DrFarkoff]

Yep did that at the start Noddy they are dry and clean , there's a single wire on the right side that is just unwinding but not restricting the throttles

But No worries on asking the question! If there were no questions then there'd be no answers!

Taa

 

[nud1e]

I know that you did, but

have you checked the vacuum take-off screws?
have you left enough slack on the cables?

 

[Ogmios]

fwiw;

i had a similar problem -probably sounds all wrong, but - it was a plug cap dying!

ooh - worth checking the choke body gasket too
HTH,
keep us posted.

 

[Rob Farmer]

Check the timing if you have a strobe. I had a similar problem with a Paralever I had. The advance retard unit was sticking in the bean can causing all sorts of strange low running problems.

Are the mixture screws set to a fixed position (ie 1/2 turn) or have you turned them to a position where the engine revs peak at tickover?

Do a compression test if you can.

 

[jaber]

A mish mash Hodge Podge of a Lovely wee scruffy Loveable Pile of Pooh! But it's a cracker

So the story so far delivered and abandoned I Did a once over inc comp check and pronounced it do~able

So fixed all the ancilliaries overhauled the alternator and starter and fitted new leads

Stripped carbs, blew out and cleaned all crud out of fuelways and fitted new diapraghms and floats (and set them), also did needles and pilot screw o rings and fitted a feck off big fuel filter to stop crud from tank.

Jets didn't look too worn when I tried the needles in them but something isn't right

She starts and Idles fine but when you rev up and release the cables are returning okay and the slides seem to be dropping okay

SO why won't she go back to tickover??? it remains at a very fast idle for a minute before it drops back

Intake tubes are fine and sealed and I can't detect an air leak and as I've said the compression check was good and fairly balanced but it's running like a bag of pooh again?

Timing is spot on and the valve clearances done too, although someone has done the zero clearance on one side to stop the rocker arms rattling off the posts

So before I launch into another whole strip and dismantle fest

Has anyone any useful and sensible suggestions which would be relevent to this wee motorcycle and it's present predicament?

Thats ironic mt r80rt has developed the same problem done exactly what you have done, worse after a good thrash revs at about 200rpm then goes back to idle very annoying cant seem to cure it HELP!

 

[DrFarkoff]

Thats ironic mt r80rt has developed the same problem done exactly what you have done, worse after a good thrash revs at about 200rpm then goes back to idle very annoying cant seem to cure it HELP!

Check your valve clearances Jaber

 

[DrFarkoff]

Well time for an Update!

I'm only doing this between other jobs to keep the time down on it so as time allows I progress bit by bit! Frustratingly

Okay the clearances were done and set at 0.1mm inlet and 0.2mm exh

Bean can removed and mechanism was a bit sticky but easily freed up and was in the retarded position rather than the advanced when I carefully pried off the inspection window

Compression check = Left Cyl 120psi and right 118psi

So What do the as we call them back home "Ould Hands" think now???

Carbs and diapraghms cleaned twice (new needles and floats and pilot screw o rings second time)

Cables are Serviceable and not sticking

Choke arms are returning by themselves

Exhaust was changed and seal is good throughout

Intake rubbers not yet changed but look serviceable and WD40 test seems to make no change

Oil level is slightly high by about 5mm but that shouldn't make that much of a difference?

Ignition timing is spot on, Ignitin leads were renewed,

Coil seems fine I would expect misfire rather than excessively high idle with coil fault???

Bike runs a tad lumpy at tickover but I think thats something to do with whatever is going on ??

My thoughts

Valve clearances and seal with the seat is good (hence high comprssion) but the Guides are worn and air is being drawn in??

Anyone else any ideas

Constructive suggestions appreciated "Matches and Tank" have been thought of but it's not Mine! Hence working between jobs

 

[triplet]

mine did the same,tryed everything then it turned out to be the tickover was set ever so slightly too high turned it down 1/8 of a turn no more probs

 

[cookie]

mine did the same,tryed everything then it turned out to be the tickover was set ever so slightly too high turned it down 1/8 of a turn no more probs

out of sync carbs will produce that effect sometimes too, but i expect you've done that.

 

[Ogmios]

long shot dept;

a loose screw(s) holding the butterfly valve in place?
(happened me on an R80 - similar symptons))
i did mention plug caps dint i
too lazy to scroll back

 

[DrFarkoff]

mention plug caps dint i

Ignitin leads were renewed,

 

[(RIP) Kaister]

same sort of thing on an old guzzi i had.

Turned out the slides were worn and leaking air.

You've got an excess of air at idle - you just need to find it.

 

[Rob Farmer]

Phils right.

Have you checked the O rings on the butterfly pivots? I had a paralever last year where these O rings were shot and leaking air.

How did you set the float heights? If you did it with the carbs inverted, as per the Haynes manual, it will be wrong.

This is from the R80G/s workshop manual. Obviously if the fuel isn't covering the idle jet you will be sucking up a small amount of fuel but the mixture will be very weak.

 

[DrFarkoff]

Yep Did it that way Rob on the bike

There are new diapaghms from motorworks which are significantly heavier than the old ones but I took off the rear intake pipes and they are operating just the same as any airhead I've ever owned

It's got me just a bit puzzled I think I'll swop intake tubes and cables off mine as they are new, Just to rule them out of likely suspect lists

Worn Slides? Haven't head of that affecting tickover this way before bad pickup and low idle Yes but high tickover no buut well worth and investigate

Thanks guys keep the ideas coming

 

[(RIP) pastyman]

Sounds to me like you are at the point of trying another carb to see if that will identify which of yours is the problem and go from there. at least that way you may only have one side to deal with. Seem to be plenty in various breakers on flebay and a spare is always worth while.
Oh. just as a matter of interest I have just tought of something.... When I first got mine, the top of the vacum cap, the bit at the top of the carb, had a rubber bung in it where the original metal cap had come out, It was leaking air ( and water ) there. I fitted a new top and that sorted it. Could be that yours might be leaking there too. Only a thought, Best of luck

 

[(RIP) Kaister]

you say it doesn't return to idle 'for a minute' ?

is that a real minute ?

or 10 sec ?

a minute may mean a physical thing, 10 sec would be mixture.

diaphragms dont affect idle, needles don't affect idle
its just the idle circuit and bypass drillings - plus air

 

[DrFarkoff]

Oh. just as a matter of interest I have just tought of something.... When I first got mine, the top of the vacum cap, the bit at the top of the carb, had a rubber bung in it where the original metal cap had come out, It was leaking air ( and water ) there. I fitted a new top and that sorted it. Could be that yours might be leaking there too. Only a thought, Best of luck

Spot On! Nice one Pastyman The Right hand carb top metal disc was bypassing air I was able to blow up the pipe and it blew out by the disc on the top but you'd never see the crack

I knocked it out and cleaned it and sorted it lightly sealed the edge with agood quality RTV and lightly peened the alloy back down to seal it so it's made a dramatic improvement checked left and it was good

Last Few wee tweeks and she can go home and I think I'll do the idle circuits again as the tank was extremely Keek! Idle on the right carb is not as good when you do the old one plug trick

 

[DrFarkoff]

you say it doesn't return to idle 'for a minute' ?

is that a real minute ?

or 10 sec ?

a minute may mean a physical thing, 10 sec would be mixture.

diaphragms dont affect idle, needles don't affect idle
its just the idle circuit and bypass drillings - plus air

30 ~ 40 seconds

Not 10 seconds

Diaphragms don't affect idle but if they're jammed up a bit off their base mark then they will overrichen the mixture at idle and it'll run like a bag of poo

Nice one about the Idle circuit I did clean it but it would just take another bit of Tank Keek to fcuk it up again!

Cheers Moto!