My new to me 2011 Beta Evo 300 4T wasn't running right this past event. I just bogged down and run it like cr@p for a while. I could barely keep it alive by playing with the throttle. Even after a new Iridium plug, it still was bogging down on full throttle, after some play with the choke on and throttle, it cleared and ran fine for the rest of the day but ruined my mojo and scared me anytime I needed a handful of throttle and I ended up chickening out.

Air filter is clean, she runs on M99 (Tesco 99 oct fuel), wiring and plug is clean.

It felt like there wasn't getting any fuel in higher revs to the engine....

 

Any suggestion where to start looking for the problem? Many thanks

Strip the carb and clean everything with carb cleaner and (if possible) ultra-sonic. Check everything in there including float height. When you put it back, be sure that the rubbers to the air box and engine are properly seated and sealed. Try it like that.

PS. Taking the carb off is a swine of a job. You'll need to remove the airbox, exhaust, the upper rear shock bolt, the ignition thingie on the right of the engine and the other ignition thingie bolted to the back of the gearbox. When you put it back together make sure that the various breather pipes are routed in a tidy manner. I've always had to use a ty-rap the keep one of them clear of the exhaust.

Just reminded me why I got a 4RT   

Hi Bonito. The 4 st engine is prone to air leaks on the exhaust joint, this allows oxygen in and causes the misfire at higher revs. Reseal using fireproof silicone and some aluminium foil wrapped around pipecovered in goo, make sure it cures before starting engine.The worst joint is between front pipe and rear silencer btw

Hope this helps.

ps also check for air leaks on inlet rubber, again prone to splitting.

Edited December 29, 20178 yr by 4banger

Is the electric fuel tap OK?

 

14 minutes ago, petert said:

Is the electric fuel tap OK?

 

I was wondering that too. How does that thing work anyway? Previous owner told me just leave it and its ok, I haven't touched it since I got the bike. I have tried various positions on the first day, but can't see any difference 

 

I suggest you also check the tank cap to make sure it is allowing air in to replace the fuel flowing out to the carb.  The cap incorporates a one-way valve to ensure fuel does not escape when the bike is upside down/on its side.

You can check two ways.  If the bike is misbehaving again, undo the tank cap completely and it it runs OK that's probably your problem.  Alternatively, remove the cap and let the air get to it to evaporate any fuel or vapour.  Then alternatively suck/blow on the tiny black breather pipe on the cap to see if allows air through one way (as if into the tank) but not the other way. 

1 hour ago, bonito said:

I was wondering that too. How does that thing work anyway? Previous owner told me just leave it and its ok, I haven't touched it since I got the bike. I have tried various positions on the first day, but can't see any difference 

 

The tap has a solenoid (an electrical coil which generates a magnetic field which attracts the centre core causing it to move and open the tap).  As soon as the engine turns over sufficient electrical energy flows to the tap to open the fuel flow.  The tap also includes an alternative setting to allow the carb to be filled with fuel (primed) in those situations such as where the bike has been out of use for some time and the carb contains no fuel.  Can't remember which position is the priming one but the owners manual shows it clearly.

If you search the Beta forum on this site there's some more info to be gained.

1 hour ago, portman said:

The tap has a solenoid (an electrical coil which generates a magnetic field which attracts the centre core causing it to move and open the tap).  As soon as the engine turns over sufficient electrical energy flows to the tap to open the fuel flow.  The tap also includes an alternative setting to allow the carb to be filled with fuel (primed) in those situations such as where the bike has been out of use for some time and the carb contains no fuel.  Can't remember which position is the priming one but the owners manual shows it clearly.

If you search the Beta forum on this site there's some more info to be gained.

found it

Where can I get the Jitsie air mixture screw for the carb in the uk?

Update, what I found so far is that the hose (silicone) carb to engine was loos. need to replace it with a rubber one, the silicone one is way to slippery. Hope that was the problem.

Found the mix screw on ebay.  

 

Thanks for all the help.

On 29/12/2017 at 7:54 PM, bonito said:

Where can I get the Jitsie air mixture screw for the carb in the uk?

Mine came from bvm

Flipped my 2016 Evo 300 4t upside down once in the bush's, took a while to get to it. Went to start it, backfired and blew the carb right out of the boot!

I have installed the Jitsie mix screw, and since I tighten the carb it has been running great. 

What a pita to get to the carb, holy cow  what an ordeal to get to it.

Only thing I wish was a bit more grunt from the exhaust and maybe a wee bit more power. Need to look for a muffler, hope they still make the Bosi titanium one. 

3 hours ago, bonito said:

What a pita to get to the carb, holy cow  what an ordeal to get to it.

It gets easier with practice.