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2017 4T miss fire on high RPM


betasweden
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Hello,

 

Seeking help with this issue.

My 2017 300 4T is running great. Except for one thing.

On really high RPMs the engine misfire. Like an Enduro 4T.

Really annoying when you need to have high RPMs on a big step with short run up.

 

Is in any kind of "RPM stop" on them?

I have changed, jets etc..

Thank full for all help!

 

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29 minutes ago, oni nou said:

Change the jets again. Changing the jets from what used to work fine if you develop  a problem is one of the avenues to go down.

Hello

It has always been this problem. Dont think it has to do with the jets. Dose not sound like that. 

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5 minutes ago, lineaway said:

The std exhaust does not breath very well. My son has an `15 with a header pipe and the factory exhaust. I would start with the a new muffle . What jets did you go to.?

What is an header pip? I have now an Bosi exhaust. But this problem was even before i changed.. 

Think Main is 137,5 right now. 

But this issue on high RPMs has been sens new :(

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15 minutes ago, lineaway said:

A 137 is pretty big, what pilot and elevation are you at. You have the complete Bosi exhaust?

Yes, i know... But i did go bigger and bigger. And stoped at 137. Could probably go back a bit. But runns ok now. And its not that fun to change on the 4T..

 No, Bosi only have an exhaust pip for 4T. Not full.. 

But should not misfire on high RPMs any way? 

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1 minute ago, oni nou said:

Did the problem start after you changed the jets or before......did you change the jets because you had them in the garage so you thought you would try them out.

As i stated, it has always been this issue. And the bike comes "lean" from factory. So you need to change from the beginning. Dose not run good at all from Factory. 

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 Yes, I think you are right that you are hitting the limiter. Beta used to sell a race kit for the 4T. Cam, valves and a hotter ignition. Supposedly the Factory model has these. Talk to your Beta dealer/importer and see if it is available. I have ridden one with these mods and with higher compression, it was a monster of a bike. And the owner was one of our top riders. Very fun machine Good luck.

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8 minutes ago, oni nou said:

If you had the problem right from when you purchased it then it must be the way they are supposed to be.

I know that Beta probably do not know if there is a rev limiter on them as they made it, but it should not misfire 

At the last trial I was at there was a rider on a Beta 4T that kept back firing so perhaps its just a quirk of those engines.

 They come from the Factory very lean. We ride at over 7000 ft and up and the jetting comes pretty good. We just rode our western Nationals. The first event at 3300 ft and second event at 800 ft. We had 3 Beta 4T`s with us. A `15 with a full pipe, a `17 factory and a `17 std. Stock is a 122. We ended up at a 130 main with a 27.5 pilot.  The mixture screw has quite a range of adjustment. Most people never jet these bikes as it is very difficult to get too. I have to rejett my son`s before we go back to our summer riding in the mountains. (Up to 10,000 ft). 

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2 minutes ago, oni nou said:

Perhaps you could talk to the dealer that you purchased it from and ask him why it is that Beta sells bikes that do not work properly and get the dealer to make an effort to try and fix the problem. If the customer has to make changes to the bike setup to make it work properly surely that is not right ..........................Would people buy a new car..find that it did not run properly and then start trying to fix the problem themselves ...................................I don't think so

 It works fine, he is running it hard and he know`s  it, Beta know`s it and they make the parts to make it rev more. :P  

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