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aj201280

New Rev 3 Mikuni Carb?

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I'v done all three mods. Drilling, float tangs mods. and atmosphere tubes mods. and now the problem is solved..;)

I think that you can see on the spark ( black or brown ) if the float level is corect..

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what exactly gets the treatment from the drill?

would be nice if the above mod works, ill try that for starters but am interested in what you guys are drilling.

Si

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The drill mod isn't necessary. Just set the floats per Billy T's instructions and nipper a hole in the vent tubes halfway up the body and it's fixed. The reason the Mikuni pees fuel out of the vent tubes is the vent tubes on the Beta are too long and end below the float bowl. If fuel gets splashed up into the tubes they can form a siphon and will flow fuel until the supply stops. Nippering a hole above the level of the float bowl kills the siphon. Any fuel that gets up into the vent tube will just go back down into the float bowl or out the end of the vent tube but it won't keep sucking fuel out of the float bowl. It really is that easy to fix.

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The float tang adjustments do the job, thanks to Billy T.

pdf here

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Hi.

I would like to show the solution I have addopted to solve the leakage problems. There is no nedd to drill, and the mod is completely reversible.

The little pipe is a brass ballpen refill. Is easyer to weld than stainless steel ones.

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I have modified two carbs, an there is no leackage, even with the bike at extreme positions.

Regards

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Hi Everyone,

Quick Update on My Beta ,

Having a blast with this bike and the whole trial riding skills.. cant beleive how much fun Im having !!!

Great choice on Going for the BETA and not the GAS GAS,,, these bikes are solid and really reliables...

Glad I heard advices from all the guys who ride in my area...

Now, Ive learned a lot in these weeks and now im noticing my bike not responding clean at higher revs in the longer climbs sections we have arround here...

Did Billy T mod, so no alarming fuel leaks... just the usual problems when going steep and long downhills , that always kinda floods teh carb and she takes the The EXTRA Kicks to fire her up when arriving down.

So, Im about Attack this problem at high revs going for the long steep climbs , on GOING DOWN 1 size on the Main Pilot , Will leave the needle POS right were I found it ( at the middle or 3rd groove ) and he usual adjust of the air screw which requieres the every PRE RIDE , adjustment... My Bike DOWN LOW low feels really good... <its just like on 3rd gear pinned going up on a long steep climb...OR a 2nd gear pre hard acceleration to attack a step rock section... just like the bikes of the guys I ride with...

What are your oppinions on going DOWN 1 SIZE ON THE MAIN PILOT ?

We are at 800mts seal level and the trail rides sometimes go up to 1200mts...

The jetting is Totally Stock.

I KNOW, I was tempted to just change the whole carb for a KEIHIN, bu rather prefer fine tunning this one..and keep those $$ down on more expenses... The carb, the both air boots, the throttlr cable... Nahhhh... Ill keep this and at least try to make it better :thumbup:

<on <hold for advices...

Thanks

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I just picked up a 2002 beta rev 3 270, and while testing in the parking lot fuel was coming out the overflow...just assumed the float was sticking as it did stop.  I'll have to have a look.

 

real quick qestion:  without pulling the fuel line to check, which petcock position is closed, open, and reserve.  the previous owner told me arrow pointing towards the cylinder is off, down-on, and back towards air boot is reserve.  Does this sound right

 

 

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My 04 bike is the opposite away from cylinder off. Up is on and towards cylinder reserve.

Reset the tangs as described above and it will stop.

Edited by richfr

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Yes toward cylinder is on. Reset tangs as per Billy Traynor's fix and nip a hole in the vent tubes above the level of the float bowl and the fuel piddle stops. It happens because the tubes are too long and once fuel gets splashed up into the vent circuits they act like siphons.

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The float tang adjustments do the job, thanks to Billy T.

pdf here

 

Just done my 2003 250, not smokey, throttle response is much better, a quick spin up the road flat out in top (It's road registered honest Constable) and no smoke trail, Now to get to the practice grounds and see if it stalls so easy downhill?

 

In my opinion this thread needs a tidy up, and get rid of some of the innapropriate posts, as the title suggests it refers to the known problem! that's why people look on this thread to start with and are looking for an answer quickly without wading through posts that tell them nothing!........Until they find this pdf  :thumbup: 

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Glad this old over the hill washed up Trials rider could help.

 

 

 

 

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Just done my 2003 250, not smokey, throttle response is much better, a quick spin up the road flat out in top (It's road registered honest Constable) and no smoke trail, Now to get to the practice grounds and see if it stalls so easy downhill?

 

In my opinion this thread needs a tidy up, and get rid of some of the innapropriate posts, as the title suggests it refers to the known problem! that's why people look on this thread to start with and are looking for an answer quickly without wading through posts that tell them nothing!........Until they find this pdf  :thumbup:

 Originally this was a pinned thread of Billy T`s Fix. (Which I used when the Rev`s were new.) Some how someone thought they had a better solution. :stupid:

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Glad this old over the hill washed up Trials rider could help.

 

Thank you very much Billy T :thumbup: Being from an automotive background all I needed was some measurements to work to, I can now say the results are amazing, took the old girl to the practice grounds today and it is amazing the difference! No bogging down on inclines, no stalling on decents, no excessive smoke, and a much more responsive engine all together, and I'm well chuffed with the results! :bouncy:

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