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aj201280

New Rev 3 Mikuni Carb?

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I made the drilling mods, too. The fuel leaking problem solved. But I don't see any differnce about the engine stalling downhill. So, I've set the fuel tangs a bit even higher, and I think that now it's ok. Still not perfect, in some really steep downhills the idle speed still decreases, but most of the time it doesn't stall.

I saw a picture here about a float extension bowl and a main jet shroud. From where can I order theese, and how much do they cost? And are they making the carb absolutely perfect?

You can buy it from your local Beta dealer. The part number is # 20.00211.000

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I have the float bowl extension on my '05 rev 3, but my question is this. Shouldn't you need a longer main jet so it actually reaches the aditional fuel? Is this what the little "extendo thingy" is supposed to simulate?

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Yeah, it is a bit like put a glass in water, so it fills up, then turn it upside down so it is full of water, you'll be able to lift it right out of the water to the rim before the water gushes out and replenished with air. The same happens in that little up turned brass cup, once fuel is in there it won't leave until air can flow down the main jet, in which case the engine will be stopped and the fuel level will rise immediately anyhow.

Bob

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How much are the float bowl extensions?

Not sure how that cup works because mine has little holes drilled in it so it would not work like an upturned glass would it?

Edited by Anotherfive

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Not sure how that cup works because mine has little holes drilled in it so it would not work like an upturned glass would it?

That ruins my theory then, unless the holes aren't right at the top.

God knows what it does to help then :D

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My '06 270 has had the Keihin carb fitted, Nigel at Inchains reckons that this was to cure the known carb problems. Anybody else running one of these. Any advantages/disadvantages.

My machine never leaks fuel, starts very easily, although i've noticed a tendency for it to stall if I don't blip the throttle on a long and very steep down hill descent.

Shaun.

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I have some additional information to the float level mod!

After you set the float level properly it's recommended to richen the mixture. If the petrol level is lower in the carb then more vacuum is needed to suck the same amount of petrol. So by setting the float level lower, your bike will run leaner (or richer if you set the float level higher). To make the bike to run the same as before, you should turn the air screw clock-wise so the mixture will be good again. I don't think that it's needed to change the jets, the air screw setting is enough.

Edited by fkrisztian
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Hi to all.

BillyT here.

Interesting to still see this topic floating around after all of these years.

The mods posted to the tangs and the hose routing solves this problem WHEN DONE CORRECTLY.

There is no need to drill any holes or add any float bowl extensions.

Granted these adjustments should have been done at the Beta factory, but they were not.

The adjustment I posted many years ago where indeed part of a standard training I received and most good carb tuners

out there are well aware of this basic adjustment. I did not invent it I just applied it.

I see too many suggestions that re-act to the symptoms and not actually addressing the problem. Kind of like taking an asprin for a

headache, the asprin only masks the reason why the headache is there to begin with.

Many new riders to a Beta or new posters to this forum are unware of the history af this carb as to why, how it ended up on a Beta.

And why the carb came from Japan (Mikuni) like it did.

:thumbup:

Take care all.............

BillyT

Edited by BillyTraynor
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Hi Billy,

Nice to see you are still lookin' out for us. I've done the carb mods many times on many bikes with the expected great results. No drilling just the vent hose and tang thing. Many thanks for the enlightenment. It has made for many sweet running Beta's in this neck of the woods. Now if you can just come up with an easy way to get that &*%$*@& Keihin to go back in place I'd be forever grateful.

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I found a description of the drill mod:

http://www.motoclubgiaveno.com/page12.html

Unfortunately the description is italian (?), but the pictures are self-explaining.

Hi all I have translated to english

I hope this helps. You will need to read between the lines though!

1) After having well washed with petrol totally dismantle the carburetor paying attention to positioning of all components.

2) Punching the central portion of the cap processing Figure 1.

3) Pierce cap with a peak of 2mm and use a small screw extractor as Parker.

4) 's support of the measure noted caliber A channel of Figure 2.

5) With a tip from 3mm to extend the hole released by the cap Figure 1. VERY CARFUL a stop at 1.5mm by the end of the channel.

6) With a tip of 2mm. Making the new Bar B of Figure 3 until you reach the canal.

7) 's aid of a compressor to clean carefully all the various steps of carburetor air blowing THOROUGHLY.

8) With the dots lead to appropriate measures ( available in any stoe hunting & fisheries), provide fill the hole of C Figure 3

and the channel for processing of Figure 1.

Paul.

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leaking doesnt bother me just going do the carb mods so i know the bike is setup properly and i think it will keep it running a bit cleaner.

Overflowing is a major problem, as the float level is above what it should be, therefore making it too rich and maybe flooding/fouling plugs. Also makes your exhaust port and pipe full of depositis.

My old Beta with a Dellorto never leaked.

Koz

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