MTX4-R acting sporadic, shifting when it wants...
 

Hey guys, I have an issue with my MTX4-R and I have no idea why. On one straight away it will shift perfectly and then on the next it will act like it has no balls and stays in first gear and then will shift perfectly in the next straight. On the long straight, I have to double tap the throttle to make it shift. Any ideas? I just made sure that the carb was sealed to the engine body but have not checked the needles. Also, the 2 speed transmission is adjusted correctly and shows very minimal wear. It was replaced at the end of last season.

Thanks for any help!
Kyle
210-722-6891

Is it not shifting because the engine rpms just aren't getting high enough or is it screaming like crazy while stuck in 1st?

If it's the first, try leaning it just a hair and the problem will probably go away.

If it's the second, the problem is the 2 speed itself. Pull it apart and inspect everything. If you don't see anything wrong, replace everything and start from scratch.

It's kind of a mix of both. Sometimes the engine will just scream down the back stretch and sometimes it will sound like its just not getting up there. My plan is to just replace all of the o rings on the carb thinking maybe and air leak and then if that is not the case, than I will put in a new 2 speed. I dont think there is anything else that could be effecting it. Right?

One of the things to look out for with the MTX-4 is the center piece that goes on the shaft that you assemble the 2-speed shoes around. The older kits had issues with that pieces rounded corners eventually rounding the channel within the shoes. This would cause that piece to stick the shoes open (keeping it engaged is second gear) or make engaging second gear really irratic. The newer kits (before the MTX-5) had the newer design center piece and shoes that reduced the 2-speed issues. Also, check the gaps between the 2-speed shoes to make sure that are even. If one side has more gap that the other (which could happen at times), it could cause some shifting issues as well.

Thank you Jlock, I did not know that. I'll just order the newer version of the 2speed so I kniw it's all good. Thanks man!
Kyle

No problems man, glad that I could help. When I was running my MTX-4, I had similar issues that drove me crazy for a while. Jeff Whiting was the racer that told me about what I passed on to you. He had the same issues when he was sponsored by Mugen at that time. Once I got the new stuff, the shifting issues stopped. :)

Excellent, I think just for good measure tho, I'm going to rebuild the carb as well. So new 2 speed and rebuild should take care of all the issues. I looked on Amain and all they show for transmission parts is the middle adapter is mtx3 and the rest is mtx4. Is that correct or is there a newer middle part?

Oh, I will have to research that bit of information. Check on www.nitrohouse.com as well. They carry a lot of Mugen stuff as well.

thanks man, i'll check it out.

Here is the link to the 2-speed adapter part from Nitrohouse:

http://www.nitrohouse.com/2-Speed-Ad...4_p_11442.html

Hey guys, I'm having a hard time finding a lot of parts for this car. Apparently everything has been discontinued. Any idea if the mtx5 2 speed will fit the 4?

Check with Robbie Collins at Mugen at their California office for details on your inquiry. I don't know much about the MTX-5 to say "yea or nay".

ok, i just emailed them and we will see what they say. i'm sure they are just going to tell me to upgrade to an mtx5 which I have been contemplating anyway or the Xray NT1 2013