When carbs go bad

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rodbargee
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When carbs go bad

Post by rodbargee »

Ok peeps perhaps this should be in tech but Im sure you'll have a view here too.
The mighty Mirage that Ive been blatting about on this summer displays a tendancy to bog a little on certain throttle openings not electricaL Im pretty sure. Hypothetically could I (waits for court gasp replace the carbs with throttle bodies and is this a good or /purist mode) total disaster (almost certainly) SECONDLY Is it really difficult? Should perhaps say the carbs have overflowed a couple of times despite new valves recently (bit sticky a tap cured that and its not done it since.
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Re: When carbs go bad

Post by 1888 »

Needle valve/seats sticking
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Re: When carbs go bad

Post by Julian_Boolean »

Carbs overflowing is caused by the float valves not sealing or the float heights are wrong, but be aware some carbs on some bikes don't like being leant over and always leak a little, Mikuni flatslides do this because the float chambers are linked and when the bike is leant over all the fuel ends up in the lowest float chamber.

The bogging on certain throttle openings can be tuned out and this is probably easier and cheaper than fitting fuel injection, if you don't want to fiddle with the carbs yourself, take it to someone who knows Laverdas, I assume it's got DellOrto slide carbs and in my experience these aren't great, though you do wonder how something as simple as a slide carb can be bad.

For fuel injection you will need the throttle bodies, a fuel pump, a way for the fuel to return to the tank plus a whole load of sensors and an ECU for it to work properly.
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Re: When carbs go bad

Post by IOU0 »

As has been said, does sound suspiciously like needle valve.
Pretty sure you could convert it all to FI for a couple of grand............or buy some new seats/valves for @ £10 ea
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Re: When carbs go bad

Post by rodbargee »

theres a bill with t for three new valves it had had a carb balance when I picked it up so they dont last long...
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Re: When carbs go bad

Post by Julian_Boolean »

rodbargee wrote: Wed Sep 16, 2020 10:10 am theres a bill with t for three new valves it had had a carb balance when I picked it up so they dont last long...
They've probably got dirt in them, the inside of your tank might be corroding, or if it's been sealed the sealant is coming off.
I've tried sealing tanks and it doesn't last, you're better off getting the bottom of the tank cut off, it cleaned properly by shot blasting and then the bottom welding back on again - not cheap, but cheaper than a new tank.

If you're going to keep the bike fix it properly, if you're not keeping it do what all the other shysters selling classic bikes do, bodge it and enjoy the profit.
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Re: When carbs go bad

Post by IOU0 »

rodbargee wrote: Wed Sep 16, 2020 10:10 am theres a bill with t for three new valves it had had a carb balance when I picked it up so they dont last long...
Were the seats replaced as well?
If you can drop the bottom of the float bowl (jet access) get some compressed air in there and see if that makes a difference!
But a carb strip is in order!
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Re: When carbs go bad

Post by JackyJoll »

Inline paper element filters stop rust and dirt going from the tank to the carbs.
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Re: When carbs go bad

Post by JackyJoll »

roadbargee wrote:a tendancy to bog a little on certain throttle openings
What throttle openings?
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rodbargee
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Re: When carbs go bad

Post by rodbargee »

4th (Of 5) Half throttle if held slightly too long.
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Re: When carbs go bad

Post by cheb »

rodbargee wrote: Wed Sep 16, 2020 10:10 am theres a bill with t for three new valves it had had a carb balance when I picked it up so they dont last long...
Can you be certain they were done, or were they just billed for?
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Re: When carbs go bad

Post by Nobby »

Emulsion Tubes worn oval. Possibly.
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Re: When carbs go bad

Post by inewham »

Do the float needles have viton tips? I've had the tips lift before If I've left the carbs standing over winter with fuel in the bowls
The petrol evaporates leaving ethanol and water which gets under the viton tip. Your new ones might be shot if they've stood a while

After changing a couple of sets I've got into the habit of turning off the petrol and letting the float bowls run dry if I don't expect to ride for more than 14days and in winter I'll even open the drain screws
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Re: When carbs go bad

Post by rodbargee »

cheb wrote: Wed Sep 16, 2020 5:32 pm
rodbargee wrote: Wed Sep 16, 2020 10:10 am theres a bill with t for three new valves it had had a carb balance when I picked it up so they dont last long...
Can you be certain they were done, or were they just billed for?
pretty sure they were replaced Ged shorten has a good rep.
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Re: When carbs go bad

Post by cheb »

That's a positive then. :clap: