4RT Engine Response On Throttle Chop

[mcman56]

I got out for a ride on a new to me 4RT and it is quite different from my Beta 300 4t.  This is a 300RR version, 2018.  Power is much sharper than the Beta but it seems like power is cut much quicker than on the Beta.  The front wheel really slams down on the backside of logs, even a small 10 inch diameter log..  I tend to double blip most any obstacle.  I'll do a second blip when the tire is on the front of the log or on top, chop the throttle, bikes roll over and set the front end down.  This 4RT just drops the front wheel like a rock hitting the ground pretty hard on the back side.  I'm wondering if this is the way fuel injection works or could it be something else. 

 

Could it have less flywheel weight than the Beta for less run on?  I put the electric start kit on but the flywheel is still very close in weight to the OEM flywheel so I don't think the starter has an effect.  Simply bouncing up and down on the suspension seems OK but I wonder if too little sag, too much compression damping or too little rebound damping makes the rear tire slam in causing the front tire to slam down.  Or is the Montesa just like that.       

[lemur]

Sounds like you are riding in first gear, 300RR will pull 3rd.  Montesa has a slightly more settled suspension compared to the Beta, not as lively suspension but the engine performance should never be lacking.

[mcman56]

Engine performance is very strong.  This is in first gear, clutch out, double blip.  I'm an old guy with damaged hands so more clutch usage would not be a good solution. 

To rephrase my question, what can make a bike nose dive on the back side of a log.  I have not been on a modern or vintage bike that did this.     
 

[lineaway]

You need a 301. They removed most of the engine braking starting with the 2020 models. My son loves his 300 for the engine braking. He hates my 301 as it acts more like a 2 stroke.

[mcman56]

engine braking - maybe but rolling on and off the throttle in first gear, my beta feels like it has more engine braking

[jonnyc21]

On front end dropping quickly maybe this might help. 

I found the suspension setup between my 2007 4RT 250 and my 2017 300RR was quit different with the 300 seeming to drop a bit quicker than the older bike.  I had had the 2007 re-valved and set it up with a little bit more squat in the rear that standard as it felt better in section riding that way.  The newer bike seemed to drop the front a bit more tell I did the same tweak to squat the rear a bit as well and that quicker drop feel went away. 

On another note I have had a good ride on a 2017 Beta 4T 300 and do to the geometry difference they feel quite different but to me most of the biggest differences seem to be suspension setup and head angle.  I suspect with some light tweaking on things you should be able to help improve any of the differences between them, however they will never be exactly the same as I am sure you already are aware. 

Good luck and hope this information helps. 

[lemur]

Cog it up one or two gears, use the clutch more and fully extend your arms 👍  1st. gear is geared so low there will always be tons of engine braking.

[mcman56]

On 1/24/2025 at 2:20 PM, jonnyc21 said:

On front end dropping quickly maybe this might help. 

I found the suspension setup between my 2007 4RT 250 and my 2017 300RR was quit different with the 300 seeming to drop a bit quicker than the older bike.  I had had the 2007 re-valved and set it up with a little bit more squat in the rear that standard as it felt better in section riding that way.  The newer bike seemed to drop the front a bit more tell I did the same tweak to squat the rear a bit as well and that quicker drop feel went away. 

On another note I have had a good ride on a 2017 Beta 4T 300 and do to the geometry difference they feel quite different but to me most of the biggest differences seem to be suspension setup and head angle.  I suspect with some light tweaking on things you should be able to help improve any of the differences between them, however they will never be exactly the same as I am sure you already are aware. 

Good luck and hope this information helps. 

Did you measure how much squat was in the back?  I added some spring preload to the forks plus more rebound damping to the shock and it feels better.  Still, the shock feels stiffer than the forks.  This bike has a fork compression damping adjustment on the bottom of the left fork leg.  The manul implies it is only effective when the forks are bottoming.  

[jonnyc21]

55 minutes ago, mcman56 said:

Did you measure how much squat was in the back?  I added some spring preload to the forks plus more rebound damping to the shock and it feels better.  Still, the shock feels stiffer than the forks.  This bike has a fork compression damping adjustment on the bottom of the left fork leg.  The manul implies it is only effective when the forks are bottoming.  

I did write it down but apparently when I moved recently I misplaced my binder with the information so regret I am not able to provide the amount different from standard.