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Beta Rev-3 270 rough running? Petrol Info?

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I have a new to me 2004 Beta Rev3 270cc and I don’t think it runs correctly but I am not sure. The bike is supposed to of had a full rebuild by the last owner including a re-plated cylinder and new piston etc. The bike start first or second kick and seems to have lots of power. What concerns me is that when you blip the throttle about 30% + it revs cleanly but then as it is dying down you get a sort of uneven roughness and a couple of loudish bangs/ coughs. I am not a mechanic and am not familiar with this engine. I don’t know if this noise is just normal overrun of excess fuel or if the carb is not set up correctly and the bike is to lean or reach? It may be low quality fuel or a problem with the timing, or if there is something more seriously wrong with the bike. Any advice would be greatly appreciated.  

As a side note should I use super unleaded or normal unleaded? The reason I ask as I have been told conflicting things. I know lots of people run super unleaded but I was told by a Beta dealer a few years ago to use normal unleaded?

What is considered old fuel and not suitable for use in bikes? I always use to think that anything older than 6 months should not be used but I have read about people saying not to use fuel that is over 30 days old.

Sorry to squeeze multiple issues in to one but I think they may be connected.

Thanks James

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I have a 2007 model and the previous owner told me to use the super unleaded (97) which I have done - I don't get the effect you describe.

Hope you get it sorted.

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Beta's handbook states to run them on "super grade unleaded".

They pink and knock on anything less than 97 ron.

 

They are also quite fussy with the float height setting due to the angle of the carb, you might find some help on here to set it, though you should be able to find a handbook to download for it on the web somewhere, any Rev 3 book from 2002 to 2007 will do.

(2000, 2001 were similar but certain parts like forks and airbox were different and 2008 had a different carb altogether)

 

If someone has had it apart, did they put it back together properly?

I'd check the timing at the very least.

Edited by goudrons

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I have a rev 3 that will pop in the exhaust when chopping the throttle off, sort of a Pop...Pop...Pop   I chased/ tried everything you can imagine to eliminate the issue but it is still there.  I tried all different fuels including race gas by the can.  Other bikes I have ridden will do that occasionally but mine does it a lot.  Otherwise, it works fine.  It was sold as a 200 and I put a 250 top end on it.  The top end is from a different year so maybe that has something to do with it.  When Beta sold 270 kits, I noticed that there were different kits for different years but I could never find out was was different.    

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Ah...yes, mine does the "pop pop" thing as well - I think it's quite normal and I quite like the sound (which comes from the exhaust). Maybe you should video it making the noise and post it so others with more knowledge than me can diagnose it?

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The popping I can get from mine is like adding up 5 or 10 of those pops.  It only happens when winding up the engine and chopping the throttle off. 

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I think if it was mine, I'd run it on super unleaded as recommended and just enjoy it - if it is running well and has power as you say, I think you should have some fun with it. 

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