Hi, I just purchased my first trials bike (2013 Beta Evo) and starting my journey in trials. I'm trying to teach myself about the mechanics of the bike so I can personally take the best care of it.

Upon purchasing the bike the idle was a bit rough. The sound of the bike would fire and give a slight jolt to the bike. The owner said the bike had been sitting a while so the carburetor most likely needed a clean.

I poured the petrol out that was in it and added 98 octane unleaded mixed with Castrol Power 1 TTS racing 2T  (70:1 ratio or 71ml to 5L) & Liqui Moly carburetor and valve cleaner (20ml).

As described in the owners manual -  EVO 250/300 2T MY13 [2013] I adjusted the idle speed which improved the performance and the jolt I was feeling before. I went to check the Air. The manual states to "From all closed recommend to 11/2 turns" From reading posts on this forum it appears that needs to be 1 to 2 turns with most people set it at 1 1/2 turns. The bad news is I could not find this valve or the screw to adjust the mixture at idling.

Any recommendations on what to look for?

Here is a video of what the bike sounds like after the idle speed adjustment. See how there is a bit of shaking at the back of the bike? Is that normal?

My next issue is that the fuel take valve doesn't shut off petrol. I thought the 20+ seconds would be enough for the engine to die. 

 

 

 

 

 

Thanks

Edited January 4, 20197 yr by Teddy
Grammar

I think the mixture screw can only be accessed from the left hand side. Adjustments should only be made with the bike fully up to temperature.

Take the fuel line off, then operate the tap so you can check if the tap is working, it takes longer than 30 secs for the engine to use the fuel in the float chamber at idle.

The air mixture screw is at back of the carb, if you look through where your exhaust is you will see it it’s a brass coloured one, you can get a adaptor for this from beta it replaces the screw and has a big head on it to adjust it when riding, if not long screwdriver will do it, as said I would take fuel pipe off and see if fuel tap is working ok the photo you put on with the purple highlight is when the mixture adapter is fitted these are hot standard 

Also when air mixture is correct the idle wants to be just above stalling speed 

add they shake like a dog crapping peach seeds!

Get a long thin flat blade screwdriver. Actually buy a couple because you’ll lose them. Grind the end round. Voila! Beta mixture adjusting tool.

Edited January 6, 20197 yr by dan williams