2017 4T miss fire on high RPM

[billyt]

The old factory Beta REV 3 4T did NOT rev out as high as the stock 4T due to the titanium valves and different cam profiles.

The Titanium valves and springs would float or flutter at higher RPM's.

The factory Rev 3 Beta 4T had a RPM limiter that was lower than stock.

It did not need to rev as high anyway due to the quicker pick of the lighter valve train.

Voice of experience...........  

 

 

 

 

 

Edited April 19, 2017 by billyt

[betasweden]

16 hours 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.

Thanks! Then i can say its not an good bike for an more expert rider. 

I hit that rev limiter every practice. .. 

Other wise it runs really good! 

[betasweden]

 

10 hours ago, oni nou said:

Have you thought about getting a 300 2 stroke.

haha been riding 300 2 Stroke for many years! 

But the Beta importer wanted me on a 4 Stroke this year  

[betasweden]

16 hours ago, timp said:

Have you tried it without the air filter?

 

It will be my first test tonight!

[carlos]

The 130 Main jet cured a lag that my 2016 Factory 300 had, needle in the middle position. Stock pilot jet. Runs and starts perfect now.

 

[carl ekblom]

It´s easy to hit the electronic rev limiter. Even I do it sometimes. The very high steps you manage to master need speed. Perhaps you should change the gearing (larger front sprocket or smaller rear sprocket). Main jet 125-130 would be fine.

[2stroke4stroke]

12 hours ago, betasweden said:

 

haha been riding 300 2 Stroke for many years! 

But the Beta importer wanted me on a 4 Stroke this year  

Can't the Beta importer answer the questions?

[betasweden]

On 2017-04-18 at 2:56 PM, timp said:

Have you tried it without the air filter?

 

I did remove the air filter last night and it was an huge difference. No misfiring almost.

But was a little bit “slow” on low register instead.

Also I removed the sparkplug and saw it was weary black.

So I will check my Main Jet and fit a 130 that I have. (Think I have 137 now..)

I know I have used the 130 before but wanted to go up to 132. But the seller did only have 137 so I took that.

But can’t remember why I wanted to go from 130 à132 (137)

Maybe a 130 and calibrate with mixture screw more will work?

 

Let me test! J

 

[betasweden]

9 hours ago, oni nou said:

Are you mad, what kind of sense does that make.

haha

[carlos]

What is your fuel mixture screw set at? Mine fell out on the trail once, ran like a bag of crap all the way back to the truck.

[betasweden]

13 hours ago, carlos said:

What is your fuel mixture screw set at? Mine fell out on the trail once, ran like a bag of crap all the way back to the truck.

I’m experimenting a little bit on that. Right now 1->2 turns out.

[carlos]

What is your fuel mixture screw set at? Mine fell out on the trail once, ran like a bag of crap all the way back to the truck.

Think mine was left at 2 1/4. Once set that should be the end of it. The larger 130 main jet was the key to getting mine to run properly.

[timp]

I get a feeling that the mixture screw should be 4 turns out?

That info may of come from Beta uk ssdt preparation list.

Try less oil on your filter. Often they are over oiled.

[timp]

Also the plug needs changing regularly.