Rotax mini evo upgraded motor bogs and dies. Help?

This topic has 8 replies, 5 voices, and was last updated 11 years, 2 months ago by Christian Fox.

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- June 11, 2015 at 10:37 am #49728
  
  Samir Shah
  Participant
  
  Check your spark plug. Is it way rich? Did you change to a much leaner jet? I am learning that the JR EVO jet is 115-125 vs 150-160 for the PREVO JR jet.
- June 11, 2015 at 10:52 am #49730
  
  Josh Dutey
  Participant
  
  Oops returned answer as email. <span style=”color: #000000; font-family: UICTFontTextStyleBody; font-size: 17px; line-height: normal; -webkit-text-size-adjust: auto;”>I put in a new plug, the denso 29 something. 30$ plug which sucks in itself. And running a 125 jet. Both karts are set up exactly the same. One runs perfect and one doesn’t. The one thing that is constant is it always seems to only have problems when on the track under load. Which things would cause that under load? I was thinking a bad battery ( didn’t get a chance to test it yet ). Other than that I’m not sure. Jetting way to rich was my first thought having a dirt bike background but the other kart doesn’t have a problem. I did see a lot of posts of people having problems with wiring being defective.</span>
- June 11, 2015 at 11:35 am #49738
  
  tony zambos
  Participant
  
  Go thru the carb for any obvious issues like floats at the wrong height or one filling with fuel. Next try swapping batteries between karts and the carbs second.
  And call your engine guy.
- June 11, 2015 at 11:56 am #49739
  
  Josh Dutey
  Participant
  
  Im going to get some testing in wensday, try swapping some parts around, unfortunately we have 2 day race following weekend which only gives me 2 days to get parts if needed. I’ve talked with my motor guy and he’s had no similar problems with any of his other evo upgrades. How exactly would you know if one side was filling with fuel?
- June 11, 2015 at 1:09 pm #49742
  
  Vincent Ciolino
  Participant
  
  Are you using the new throttle stop sleeve that they just started to include with the upgrade kits? Also, make sure that you are using rubber mounts on both the ECU and Coil. I did not have one on the coil and it shorted out, it actually melted and was replaced by warranty. I noticed the new throttle sleeve resolved a lot of the carburetor issues.
- June 11, 2015 at 1:39 pm #49743
  
  tony zambos
  Participant
  
  Josh,
  as a reference, download the article by John Savage on Rotax carbs. It’s pre-EVO. Go to http://www.karting1.co.uk/jetting-karting.htm and at the bottom of the page, click on Rotax Jetting Secrets. The floats are opaque so you’ll see fuel in the one that’s leaking. Use caution in putting the floats back in the carb, ALTO = UP.
  Non-EVO things to check:
  * fuel line that’s been pinched or kinked.
  * fuel & pulse lines firmly seated at all the connections.
  * Clogged fuel filter, either an external or internal to the carb.
  * With engine running on the stand, wiggle the wire harnesses & the plug wire.
  * Possible bad clutch.
  * The idle and air screws on the carb set the same on both carbs.
  * Nothing left inside the air box.
  Good Luck.
- June 11, 2015 at 2:11 pm #49745
  
  Josh Dutey
  Participant
  
  I didn’t receive any throttle stop sleeves and my upgrades shipped from max speed on May 29th. When did they start including them? I do have both rubber mounted. Thanks for all the information guys!!
- June 11, 2015 at 4:29 pm #49750
  
  Christian Fox
  Participant
  
  Josh, the throttle stop is for Micro only. You are fine there. Have you stripped and cleaned the carb? A tiny particle of dirt in the main jet will cause the exact problem you are having. The carb is so huge it’s very easy to work on. I would swap coils and ECUs between the motors just to check, although the electrical issues usually prevent the motor from starting in the first place. And try a different plug…you can order Densos from Amazon at great prices. Rotax motors nuke plugs…a plug that won’t start a Rotax will fire up another motor just fine. Good luck!
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