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betasweden

2017 4T miss fire on high RPM

36 posts in this topic

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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13 minutes ago, betasweden said:

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!

 

 

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.

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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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 The standard or the factory?

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1 minute ago, lineaway said:

 The standard or the factory?

 

Sorry, Standard 2017. 

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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.?

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

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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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14 minutes ago, betasweden said:

Hello

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

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.

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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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Just now, betasweden said:

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? 

Maybe you need to set the valves up to service limits or mess about with the jetting some more.

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6 minutes ago, oni nou said:

Maybe you need to set the valves up to service limits or mess about with the jetting some more.

The bike is almost new. 

But is there any RPM stop on them? 

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Posted (edited)

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.

Edited by oni nou

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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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