Hi all,

 

I'm a lucky guy that will throw a leg over a new Beta Evo 250 4T in few days. I came across this information about carb settings

 

 

 I understand that homologation requirements are on the lean side and the bike should run with the competition settings.  I have a pair of questions:

- What means 'spacer'? In what part of the carb is located?
- Are you, beta 4T users, in agreement with the recommended settings?
- Are the needed jets supplied in the crate?

Well, three of them.  Sorry...

 

I hope to share with you my new Beta-times.

Cheers,

JM

Mine is still as it came with no issues other than a backfire on the road mainly when running with throttle closed.

Hi Timp,

 

  Thank you for your feedback.  Maybe your bike has been modified in the PDI with the 'competition settings'?  By the way, is it yours a 2016?

 

Cheers,

 

JM

2015 model.

I would ring Lampkins for advice before fiddling. The carb is quite complex and not easy to work on. You can't actually adjust the mixture screw without removing the carb.

Thanks again, Timp. 

 

Those mikunis are really bizarre in trials, but work very well in other applications.   The mixture screw is located in the rear, with vertical orientation, I suppose?   I'm really dangerous fiddling with sensible parts, but can't resist!  A search in TC forums has revealed that Betas 4T of previous years came with lean jetting to overcome homologation.  Maybe yours also, and Lampkins fixed it in PDI before send your bike.

 

I would pleased to ring Lampkins, but I live in Spain...

 

Cherrs,

 

JM

You could always email them

I'll do, for sure. However, the main question still stands. What are the jets on your bikes?

Subscribed to this topic. Interesting that with the much bigger slow jet the mixture screw gets turned in. Also you can adjust the screw which is a flat head with the bike in tact, it's just not easy.

Also curious to learn about this spacer?

   

   

 

Sorry?

Hi,

  I self-answer to me: the bike comes with a catalysed exhaust and the concomitant air-injector (at least, in Spain).  I just trashed them and fitted the clean exhaust supplied apart.  In the same box, there  are an homologation kit with, among others, the small jets.  So, I suppose the big ones are fitted on the bike.

  The only thing I haven't discovered is the 'spacer'.  There is a 2x5 cm approx. tang that seems to be a external stop for the carb butterfly, but I have no idea (neither the manual).

Cheers,

JM

Ok, I think my bike (2015 300 4t) is dialed in.

 

How you know your bike isn't dialed in:

1. It doesn't start as easily as this: https://www.youtube.com/watch?v=0_mTyAw0MoI

2. You can't tell the difference between the maps - poor jetting masks the difference

3. Fan never shuts off

4. Bike backfires under engine braking

 

My bike has a 127.5 main, 22.5 Slow Jet, 60 start jet. That's how I got it from the dealer that dialed it in for a year. I'd rather have the settings on the chart to be honest as I think the slow jet is too small and I trust the manufacturer more. Anyway he also put a different CV spring in (lighter) for more snappy response, but don't worry about that. I would simply recommend the 'Competition' settings listed on the chart at the top of this thread. The 'Spacer' is simply a little metal ring on top of the Needle. Mine is still on there. I was going to take it off, but since I have a larger than normal main jet I figured I'd leave it.

 

My bike ran poorly because the air screw needed another turn out, but more importantly the rubber cap on the kickstarter side of the bike that covers a metal vent tube from the carb had perished and split, which caused the bike to run lean. Check this. Fixing it transformed my bike.

 

I was very daunted taking the carb out, these bikes are very fiddly and the air boots and jubilee clips are very hard to work with. I just took my time and all was good. What cemented my decision to do this was the fact that I rode a friends Montesa 4rt and it seemed much more powerful with 40cc's less!

 

 

I think this is the spacer:

 

Here is the cap that splits. IF SOMEONE COULD TELL ME WHERE THE RUBBER HOSE TO THE LEFT IS SUPPOSED TO GO I WOULD REALLY APPRECIATE IT! I think it just vents to the atmosphere?

 

Thank you very much for your input and the photgraphs!  I would also stick to the manufacturer's recommendations.  I can't figure out what is the point of the 'spacer' above the circlip (?).

 

I think that these hose on the left-down of your last photo is just a vent to allow the operation of the membrane that holds the needle.  Or to vent the float chamber, maybe?  I'll keep an eye on these faulty cap.  Thank you for the tip.

 

And finally, a stupid question:  The choke knob has 3 positions.  I supose that the outer is for cold start, but... Should be in the middle or in the inner position for normal riding?

 

Cheers!

 

JM