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Beta rev 4-t 300 sometimes running unstable

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Hi all,

I have a rev 4-t 2008 racing.

Most of the time it runs fine.

But after some time it starts to runs unstable stationary (misfires?).

Also sometimes the engine stops in the middle of a nonstop. After a kick it runs fine.

Does any of the above sounds familair to anybody?

Or maybe someone got any advise?

Thanks in advance.

Edited by Rollo

Hi rolo, check the thread out below " lampkins silsden " had a problem with our beta 300 evo 4t.

regards Mike.

  • Author

Thanks Mike, a good idea to start with, replacing the cdu unit. Only my bike is not an evo. maybe some other suggestions?

Hi all,

I have a rev 4-t 2008 racing.

Most of the time it runs fine.

But after some time it starts to runs unstable stationary (misfires?).

Also sometimes the engine stops in the middle of a nonstop. After a kick it runs fine.

Does any of the above sounds familair to anybody?

Or maybe someone got any advise?

Thanks in advance.

Mine was exactly the same. The bikes come with jetting that is way too lean, and causes this problem. The carb is the same as that used on the Yamaha Raptor, so you can get parts from the Yamaha shop.

You want to start here:

Pilot jet: 22.5

Main jet: 130 to 135

Air screw: 2 3/8 turns out

Needle clip: 2nd slot down from the top (thick washer below clip and thin washer above)

Once done, it was a totally different bike and ran smooth as silk, with perfect idle.

As he said.

Is the carb clean?

Check fuel is running through the fuel tap and filter.

Check there are no blockages to the fuel tank air vent.

  • 5 months later...
  • Author

Mine was exactly the same. The bikes come with jetting that is way too lean, and causes this problem. The carb is the same as that used on the Yamaha Raptor, so you can get parts from the Yamaha shop.

You want to start here:

Pilot jet: 22.5

Main jet: 130 to 135

Air screw: 2 3/8 turns out

Needle clip: 2nd slot down from the top (thick washer below clip and thin washer above)

Once done, it was a totally different bike and ran smooth as silk, with perfect idle.

@DGShannon

I've cleaned my carb and made a picture of the needle, is this the setting you mentioned?

I've changed the clip to the position marked with the arrow.

In my opinion this way the needle gets more lifted, so a richer mixture gets in the engine.

image_url-10868-1326650029.jpg

Put the clip on the bottom so the needle is raised right up and the bike will have a much stronger mid range

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