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darco

beta rev3 modifications through the years?

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hello guys, just bought a 2001 rev3 250

and i want to know what modifications have been made to the rev3 through the years

i know mine is the one with the stupid airbox, airfilter. i also know mine is the one with the mikuni carb. the dellorto carb comes from 2004 on?

and if i want to change my airbox with the newer model can i simply do that or it doesn't fit? also are is the frame the same til 2008?

i haven't been riding it since i have to do some work on it, but i read that the mikuni carb has a problem stalling, i found an dellorto phbs26 at a very cheap price, i think that model is from the gasgas txt, will it fit?

thanks in advance

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D/O carb may fit   BUT    you will have trouble adjusting the idle and the idle mixture. To change to a D/O carb you will need a right hand model. To change airbox you will need to change to the 2 piece rear frame   m/y 2002 to 2008  ,   and also change the r fender to a    m / y   2002  to 2006  , as well as the airbox

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 There is no reason to do either mod. They only went to the Del Orto one year and it did not carb well. In 2008 they had a Keihen and it ran the best. I had three 2001 Rev 3`s and they all worked great. But then again they were new.

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Well, about the airbox you are right, it s no need to change it. And for the carb, well, i got the bike from a friend and he told me that the bike will start very hard if i leave it sittint with the fuel button on.

A problem i have with it is that the front brake doesn't have power at all, i mean it is very weak, if the bike is moving and i brake it will.never block the wheel. I was thinking to start with changing the brake pads but I'm not sure that those are the problem.

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Yes, start with pads as those could be contaminated with oil. And yes, if you leave the fuel on it could flood the motor.

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this flooding thing is driving me crazy

i started the trials in the morning for a few minutes, then i started working on it and left the fuel on because i forgot, i worked on it for maximum an hour, i tried starting it now and it wont start, its flooded again, i got the spark plug out, kickstarted it a few times, etc, still i couldnt start it again. i left it with the spark plug out cause i think this way it will dry until tomorrow. anyways i had a gas gas txt before and i regret buying this beta

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ok, i did the setting in the link above,

i opened up the carb, did the thing, assembled the carb back and it does the same thing as before, if i leave the gas on the carb start pouring gas through the lower hose until i shut the gas of, and that is at a stand still.

tell me something guys, i know that 2002 onwards has a keihin carb, is that right? will that carb fit my bike? or what other carb should i get, i just had enough with this one.

actually i think im wrong, is the dellorto carb next?

38207405_2166489526757015_6100809814844112896_n.jpg

Edited by darco

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The Mikuni is quite a good carb when tuned and you may be confusing some things here. The classical definition of flooding an engine comes from the days of carburetors in cars that had accelerator pumps. If the engine wasn't running and you pumped the throttle too many times the intake manifold was full of fuel often fouling plugs with gas. These carbs don't have accelerator pumps so that can't happen.

The problems commonly ascribed to the Mikuni is a condition where fuel gets splashed up into the vent tubes for the float bowl and then continues to flow because the vent tubes are too long and end below the float bowl causing them to act like siphons. The vent tubes are the two hoses that come out of the sides of the carb. The other hose that comes out of the bottom of the carb is the overflow for the float bowl. If fuel is pouring out of the overflow your float valve is malfunctioning. This could be an assembly issue, floats rubbing on gasket, adjustment way off or a worn /damaged float valve.

First off remove the carb and nip a small hole in both of the vent tubes about halfway up the carb body. This kills the siphon action and any fuel that gets splashed up into the tube will just flow out the tube or flow back into the float bowl. While you have the carb off open the float bowl and make sure the floats are not rubbing on the float bowl gasket. If the show and wear marks trim the gasket with an X-Acto or similar razor knife. Make sure there is no gas in the floats as they can spring leaks and hold the valve open. Check adjustment for float height and travel (that little tab that's bent at a 90 degree angle and hits the tower the float pivot pin goes in). The valve only needs to open a few mm. More than that and you won't get anymore fuel flow but the floats will slam around causing the mixture to be inconsistent over rough terrain. This tab is usually set to allow far too much float travel.  Check the Viton tipped needle for debris or damage and same for the brass valve seat. Big advantage of the Mikuni is the replaceable valve assembly. The Keihin is just machined into the body.

All the instructions for soldering tubes and drilling extra vent holes is overkill. Nipping the holes in the tubes works.

As for starting issues that generation of Betas was infamous for the ignition trigger coil going bad. It's easy to think the problem is caused by the dribbly carb but it was often not the root cause.

...and I hate Del'Ortos

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thanks for the info, my english is quite good but not in technical terms like this, but ill go to a mechanic.

so can you guys tell me what carbs fit my rev3 2001?

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Maybe some pics help, i did the float level as in the link above, i did hole the hoses...

IMG_20180802_180739.jpg

IMG_20180802_180706.jpg

IMG_20180802_180655.jpg

IMG_20180802_180638.jpg

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i figured it out, its the float level needle, i need another one, does anybody know if one from a keihin ktm/beta would work? or i need to buy it original from beta.

rev3 mikuni float level needle.jpg

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